publications of the 1NSTITUTE of MARINE SCIENCE EDITOR'S NOTE This is a special issue entirely devoted to papers summarizing part o/ the extensive unpublished reports on. oysters and their relationship to the oil industry prepared /rom 1947 to 1960 as part o/ projects 9 and 23 o/ the Texas A and M Research Foundation. As part o/ its responsibüity /or dissemination o/ knowledge in the marine sciences, the Publications o/ the lnstitute o/ Marine Science joins the Texas A and M Research Foundation in publishing at joint expense summaries o/ this important work. Volume7 For 1961 Published by the lnstitute of Marine Seience The University of Texas Port Aransas, Texas July, 1962 PUBLICATIONS OF THE INSTITUTE OF MARINE SCIENCE lssue Volume Number Year Pages tList Price First 1 1 1945 190 (out of print) Second 1 2 1950 194 (out of print) Third 11 1 1951 212 2.15 Fourth 11 2 1952 215 2.40 Fifth III 1 1953 224 2.15 Sixth III 2 1954 131 (out of print) Seventh IV 1 1955 302 2.65 Eighth IV 2 1957 341 4.15 Ninth 5 1958 492 4.40 Tenth 6 1959 403 4.15 *Eleventh 7 (This issue) 1961 319 4.15 * Beginning with Volume 7, regular subscription to the Annual Volume is $4.15 per year. t Prices include postage. Please add 2% sales tax. publications of the INSTITUTE of MARINE SCIENCE EDITOR'S NOTE This is a special issue entirely devoted to papers summarizing part o/ the extensive unpublished reports on oysters and their relationship to the oíl industry prepared from 1947 to 1960 as part o/ projects 9 and 23 o/ the Texas A and M Research Foundation. As part o/ its responsibility for dissemination o/ knowledge in the marine sciences, the Publications o/ the lnstitute o/ Marine Science joins the Texas A and M Research Foundation in publishing at joint expense summaries o/ this important work. Volume 7 For 1961 Published by the lnstitute of Marine Science The University of Texas Port Aransas, Texas July, 1962 Puhlications of the Institute of Marine Science Volume 7 HowARD T. OouM, Editor MRs. ANNE WILKEY, Technical Editor MRs. JoHNNIE MoRGAN, Typist The Publü:ations of the lnstitute of Marine Science is printed annually by The Uni­versity of Texas and includes papers of basic or regional importance by Gulf workers or on Gulf waters in Marine Science and related fields of Bacteriology, Botany, Chemistry, Geology, Meteorology, Physics, and Zoology. Papers are read by three referees; papers by the editors are processed by the Chairman of the Budget Council. EDITORIAL ADVISORY COMMITTEE OF THE PUBLICATIONS W. Frank Blair, Department of Zoology, The University of Texas, Austin, Texas. Harold C. Bold, Department of Botany, The University of Texas, Austin, Texas. Albert Collier, A &M College of Texas, Galveston, Texas. R. L. Folk, Department of Geology, The University of Texas, Austin, Texas. Marcus A. Hanna, Gulf Oíl Corporation, Houston, Texas. Willis G. Hewatt, Department of Biology and Geology, Texas Christian University, Fort Worth, Texas. Donald W. Hood, Department of Oceanography, A &M College of Texas, College Station, Texas. Sewell H. Hopkins, Department of Biology, A & M College of Texas, College Station, Texas. Clark Hubbs, Department of Zoology, The University of Texas, Austin, Texas. Edward lonas, Department of Geology, The University of Texas, Austin, Texas. R. J. LeBlanc, Shell Oíl Company, Houston, Texas. Howard T. Lee, Marine Division, Texas Game and Fish Commission, Rockport, Texas. W. Armstrong Price, Wilson Building, Corpus Christi, Texas. Cecil Reíd, Sportsmans Club of Texas, Austin, Texas. Robert O. Reíd, Department of Oceanography, A & M College C!Í Texas, College Station, Texas. Studies on Oysters in Relation to the Oil lndustry JoHN G. MAcKIN AND SEWELL H. HoPKINS Table of Contents Pages Preface V List of Unpublished Reports Deposited in Libraries ------------------------------------------------v1 Organization and Acknowledgments, Projects 9 and 23 --------------------------------------viii Studies on Oyster Mortality in Relation to Natural Environments and to Oil Fields in Louisiana. fohn G. Mackin and Sewell H. Hopkins ----------------------1 Oyster Diseases Caused by Dermocystidium marinum and Other Microorganisms in Louisiana. f ohn G. Mackin --------------------------------------------------------132 A Study of the Effect on Oysters of Crude Oil Loss from a Wild Well. fohn G. Mackin and A. K. Sparks ------------------------------------------------------------------230 Canal Dredging and Silting in Louisiana Bays. fohn G. Mackin --------------------------------262 Publications of the lnstitute of Marine Science, Cumulative Contents, 1945-1961 __ 315 Preface In the Louisiana parishes of Plaquernines, Jefferson, Lafourche, and Terrehonne there is a large cornrnercial production of oysters, Crassostrea virginica (Grnelin), on bottorns leased frorn the state by individuals. The oysters on these leases are the prívate property of the leaseholder, by law. In 1946 and 1947 a nurnber of the leaseholders filed claims, sorne of which later becarne law suits, asking cornpensation for the clairned financia] losses. These clairns were based on abnorrnally high rnortality of oysters on their·1eases, allegedly caused by operations of certain oil and sulphur cornpanies. Severa] of the oil cornpanies asked the Texas A & M Research Foundation, an independent non-profit organization with headquarters on the campus of the Agricultura] and Mechanical College of Texas, to undertake at their expense an impartía] scientific investigation of the extent and cause of oyster rnortality in Louisiana and Texas. Frorn the beginning, scientists of The University of Texas, Texas Christian University, and Louisiana State University, as well as the A & M College of Texas, were enlisted in this large cooperative research project, which ultirnately cost over 2 million dollars. The researches directed by the senior scientists served to train rnany young chernists and marine biologists, and becarne widely known in the region as "projects 9 and 23." Most of the findings have not heretofore been published. The original reports of Projects 9 and 23 that bear on this question are listed under "Literature Cited" and indicated by an asterisk. A few of these reports were later pub­lished in whole or in part, but rnost are in rnanuscript form only. A set of "processed" (rnirneographed or lithoprinted) reports, including rnost of those cited here, has heen sent to each of the institutional libraries narned below. Extra copies of. sorne of these reports are still available and will be sent to any institution or individual who will agree to pay postage and packing costs. The list of available reports will be rnailed by either of the authors on request. Sorne additional reports that are not on the list have been deposited in the libraries of Virginia Fisheries Laboratory and of the United States Bureau of Cornrnercial Fisheries, Annapolis, Maryland. Copies of these and ali other reports rnay be obtained on 30-day loan frorn the authors. The following 28 libraries were each fumished with a set of the reports that were available in sufficient nurnber to permit distribution. Agricultura] and Mechanical College of Texas, Oceanography and Meteorology Library, College Station, Texas. Bingharn Oceanographic Laboratory, Y ale University, New Haven, Conn. Biological Station, Fisheries Research Board of Canada, St. Andrews, New Brunswick, Canada. Chesapeake Bay lnstitute, Johns Hopkins University, Baltirnore, Md. Chesapeake Biological Laboratory, Solornons, Md. Duke University Marine Laboratory, Beaufort, N.C. Florida State Board of Conservation, Marine Laboratory, St. Petersburg, Fla. Hawaii Marine Laboratory, University of Hawaii, Honolulu, Hawaii. lnstitute of Fisheries Research, University of North Carolina, Morehead City, N.C. lnstitute of Marine Science, University of Texas, Port Aransas, Texas. Louisiana Departrnent of Wild Life and Fisheries, New Orleans, La. Narragansett Marine Laboratory, University of Rhode Island, Kingston, R.I. Oceanographic lnstitute, Florida State University, Tallahassee, Fla. Pacific Biological Station, Fisheries Research Board of Canada, Nanaimo, British Columbia, Canada. Pacific Marine Station, College of the Pacific, Dillon Beach, Calif. Rutgers University, Department of Zoology, Ntw Brunswick, N.J. Scripps Institution of Oceanography, La ]olla, Calif. Texas Game and Fish Commission Marine Laboratory, Rockport, Texas. U.S. Bureau of Commercial Fisheries, Gulf Fishery lnvestigation, Galveston, Texas. U.S. Bureau of Commercial Fisheries Biological Laboratory, Gulf Breeze, Fla; U.S. Bureau of Commercial Fisheries Biological Laboratory, Milford, Conn. U.S. Fish and Wildlife Service Library, Woods Hole, Mass. University of British Columbia Institute of Oceanography, Vancouver, B.C., Canada. University of Delaware Marine Laboratory, Lewes, Del. University of Georgia Marine lnstitute, Sapelo Island, Ga. University of Oregon Library, Eugene, Oregon. University of Washington Fisheries-Oceanography Library, Seattle, Wash. Virginia Fisheries Laboratory, Gloucester Point, Va. LIST OF UNPUBLISHED REPORTS DEPOSITED IN LIBRARIES Boswell, J. L. March 20, 1950. Report on experiments to determine the effects of a surface film of crude oil on the absorption of atmospheric oxygen by water. 6 pp. Mimeo. Boswell, J. L. July 6, 1950. The effect of crude oil on oysters ( Gowanloch method). 35 pp. Mimeo. Brown, S. O. May 31, 1950. Microbial oxidation of crude oils and water soluble frac­ tions of crude oil as shown by the B.O.D. method. 2 pp. Mimeo. Brown, S. O. and Virginia Van Horn. May 31, 1950. Aerobic and anaerobic oxidation of crude oils by microorganisms from Louisiana bay-bottom muds. 4 pp. Mimeo. Brown, S. O. and Bobby L. Reid. May 31, 1950. Report on experiments to test the diffusion of oxygen through a surface laycr of oil. 5 pp. Mimeo. Brown, S. O., Virginia Van Horn and Bobby L. Reid. May 31, 1950. Decomposition of organic compounds by mar~ne microorganisms. 11 pp. Mimeo. Cauthron, F. F., J. G. Mackin and S. H. Hopkins. December 7, 1951. Experiments to test the effects of shell-drilling and mud-injection upon oysters, 1948. 45 pp. Mimeo. Hewatt, W. G. July 26, 1950. Studies on dissolved oxygen content and hydrogen ion concentration in the waters of Barataria Bay, Louisiana, 1945-1947. 11 pp. Mimeo. Hewatt, W. G. (No date: circa 1951). An oyster feeding experiment. 28 pp. Mimeo. Hewatt, W. G. June 15, 1951. Salinity studies in Louisiana coastal embayments west of the Mississippi River. 156 pp. Mimeo. Hewatt, W. G. May 22, 1953. Ecological studies on salt marsh ponds in southern Louisiana. 38 pp. Multilith. Hewatt, W. G. June 15, 1953. An oyster mortality study in Lower Barataria Bay, Louisiana. 11 pp. Mimeo. Hewatt, W. G. August 12, 1953. Climatological and hydrological records on the Barataria Bay area, Louisiana. Part 11. 44 pp. Multilith. Preface Vll Hopkins, S. H. Novernber ll, 1948. Notes for a working hypothesis of the causes of oyster rnortality in Louisiana and Texas. 9 pp. Mirneo. Hopkins, S. H. February 1, 1950. History of sorne oyster rnortalities reported in foreign countries. 21 pp. Mirneo. Hopkins, S. H. February, 1950. A. brief list of references on oyster rnortality in sorne foreign countries. 5 pp. Mirneo. Hopkins, S. H. July 20, 1950. The inter-relationship of weight, volurne, and linear rneasurernents of oysters and the nurnber of oysters per Louisiana sack rneasure. 14 pp. Mirneo. Jensen, F. W. and W. M. Potts. January 16, 1953. Mud sarnples and analyses. Part 11. Volatile hydrocarbons, carbon tetrachloride extra~ts, and unsaponifiable residues in rnuds. 58 pp. Mirneo. Lunz, G. R., Jr. May 2, 1950. The effect of bleedwater and of water extracts of crude oil on the purnping rate of oysters. 107 pp. Mirneo. Mackin, J. G. April 11, 1950. Report on a study of the effect of application of crude petroleurn on salt grass, Distichlis spicata (L.) Greene. 8 pp. Mimeo. Mackin, J. G. April 12, 1950. A cornparison of the effect of application of crude petroleurn to rnarsh plants and to oysters. 4 pp. Mimeo. Mackin, J. G. April ll, 1950. A report on three experirnents to study the effect of oil bleedwater on oysters under aquariurn conditions. 5 pp. Mirneo. Mackin, J. G. April 19, 1950. The effect of crude petroleurn on oysters heavily in­fested with Polydora, Cliona, and Martesia. 5 pp. Mimeo. Mackin, J. G., Billy Welch and Charles Kent. April 10, 1950. A study of rnortality of oysters ofthe Buras area of Louisiana. 49 pp. Mirneo. Mackin, J. G. and D. A. Wray. February 1, 1949. A study of mortality and mortality­producing agencies in Barataria Bay, Louisiana. 73 pp. Mirneo. Mackin, J. G. and D. A. Wray. August 8, 1950. Report on the second study of mor­tality of oysters in Barataria Bay, Louisiana, and adjacent areas. Part I. 49 pp. Mirneo. Mackin, J. G. and D. A. Wray. August 9, 1952. Report on the second study of rnortality' of oysters in Barataria Bay, Louisiana, and adjacent areas. Part II. 59 pp. Mirneo. Menzel, R. W. July 27, 1950. Report on oyster studies in Caillou Island oil field, Terrebonne Parish, Louisiana. ll6 pp. Mirneo. Menzel, R. W. August 9, 1950. Report on oyster studies in Lake Felicity and Bayou Bas Bleu, Terrebonne Parish, Louisiana. 70 pp. Mirneo. Menzel, R. W. August 12, 1950. Report of oyster investigation at the Dog Lake oil field, Terrebonne Parish, Louisiana. 13 pp. Mirneo. Menzel, R. W. January 6, 1951. Report on oyster studies at Lake Pelto oil field, Terrebonne Parish, Louisiana. 20 pp. Mirneo. Menzel, R. W. and S. H. Hopkins. Septernber 11, 1951. Report on experiments to test the effects of oil well brine or "bleedwater" on oysters at Lake Barre oil field. Volume 11. 126 pp. Mirneo. Menzel, R. W. and S. H. Hopkins. July 21, 1951. Report on cornrnercial-scale oyster planting experirnents in Bayou Bas Bleu and in Bay Sainte Elaine oil field. 218 pp. Mimeo. Menzel, R. W. and S. H. Hopkins. August 3, 1953. Report on oyster experirnents at Bay Sainte Elaine oil field. 208 pp. Multilith. Menzel, R. W. and S. H. Hopkins. July 24, 1954. Studi~ on oyster predators in Terrebonne Parish, Louisiana. 156 pp. Multilith. Prokop, J. F. May 29, 1950. Report on a study of the microbial decomposition of crude oil. 81 pp. Mimeo. Prokop, J. F. August ll, 1950. lnfection and culture procedures employed in the study of Dermocystidium marinum. 25 pp. Mimeo. Seiling, Fred W. June 26, 1951. Experiments on the effects of seismographic explora· tion on oysters in the Barataria Bay region, 1949-1950. 59 pp. Mimeo. Seiling, Fred W. April 20, 1953. Experiments on the effects of seismographic explora· tion on oysters. 11 pp. Mimeo. ÜRGANIZATION AND AcKNOWLEDGMENTs, PRoJECTS 9 AND 23 Project 9 began February 1, 1947, and ended May 31, 1950. Project 23 began June 1, 1950, and was still continuing in 1960. Project 9 was a contract research project originating in the Department of Biology, Agricultura! and Mechanical College of Texas, and sponsored by the Texas Company (now Texaco, lnc.), Humble Oil and Refining Company, The California Company, Tide Water Associated Oil Company (now Tidewater Oil Company) , Phillips Petroleum Company, and Shell Oil Company. The same six companies plus Gulf Refining Company became joint donors of Project 23, which originated in the Department of Oceanography and Meteorology, A & M College of Texas. The original contract specified that the Foundation should conduct to conclusion a thorough, scientific and impartial research to determine whether or not an abnormal oyster mortality was occurring or had occurred during the past 12 months in Louisiana or Texas waters near operations of the sponsoring companies, the degree of abnormal mortality, if any, its cause, and, if connected with oíl company operations, exactly how it was connected. As outlined in a memorandum by Dr. A. A. Jakkula (1947), Executive Director of the Texas A & M Research Foundation, on July 15, 1947, Project 9 had the following research divisions: Bacteriology under Dr. S. O. Brown of the A & M College of Texas, Chemistry under Dr. F. W. Jensen of A & M, Ecology under Dr. Willis G. Hewatt of Texas Christian University, Field Studies on Oysters under Dr. J. G. Mackin of A & M, Geology under Professor S. A. Lynch of A &M, Library under Dr. C. C. Doak of A & M, Parasitology under Dr. H. J. Bennett of Louisiana State University, Pathology and Histology under Dr. S. O. Brown of A & M, and Physiology under Dr. E. J. Lund of The University of Texas. The Parasitology division did its work at Grand Isle and at the Baton Rouge campus of L.S.U., and Physiology was centered at the lnstitute of Marine Science of The University of Texas, Port Aransas. Dr. Hewatt of the Department of Biology and Geology, T.C.U., continued a study of the hydrobiology of Barataria Bay that he had been engaged in before Project 9 started. Dr. S. H. Hopkins was Director of Project 9, Dr. J. G. Mackin was Director of Field Work and Assistant Director of Project, and Dr. C. C. Doak was Coordinator. The consultants listed in the 1947 outline were Dr. Thurlow C. Nelson of Rutgers University, Dr. Herbert F. Prytherch of the U. S. Fish and Wildlife Service, Dr. C. R. Elsey of British Columbia Packers, Dr. Claude E. ZoBell of Scripps lnstitution of Oceanography, and Mr. H. A. Marmer of the U. S. Coast and Geodetic Survey. In 1942 Dr. P. Korringa of Bergen op Zoom, the chief shellfish biologist of Holland, was added to the list of consultants. All of these men inspected work in progress in the laboratory and in the field and gave valuable advice based on first-hand study of the procedures of Foundation workers. A revised plan of organization and a personnel chart for Project 9 were prepared by Dr. Jakkula on July 3, 1948. The chart is shown in Fig. l. The research divisions were now listed as Bacteriology, Biological Technique, Chemistry, Ecology and Hydro­biology, Geology and Hydrography, Oyster Biology, Parasitology, and Physiology. Ecology and Hydrobiology was headed by Dr. Hewatt at Texas Christian University, Oyster Biology by Dr. Mackin at Grand Isle, Parasitology by Dr. Bennett at Louisiana State University, and Physiology by Dr. Lund at Port Aransas (lnstitute of Marine Science). Ali other divisions had headquarters at the A & M College of Texas, under Dr. Brown (Bacteriology and Biological Technique), Dr. Jensen ( Chemistry), and Professor Lynch ( Geology and Hydrography). The duties and activities of each research division were outlined in a mimeographed memorandum of the same date. Under Chemistry 22 different phases of research were listed, under Oyster Biology 26, and under Physiology 9. Still other studies were added later. Sorne of these were conducted by persons at other institutions. Special bacteriological studies were carried out in the laboratory of Dr. Claude E. ZoBell at Scripps lnstitution of Oceanography, La Jolla, California. Physio­logical experiments were run at Bears Bluff Laboratories, W admalaw lsland, South Carolina, under the direction of Mr. G. Robert Lunz, Jr. Mr. Fred Sieling of the Mary­land Department of Research and Education directed a special field study of the effects of seismographic exploration on oysters at two localities in Louisiana. An annotated bibliography of oysters (794 pages) was compiled by Mr. J. L. Baughman of the Texas Game and Fish Commission and published by the Foundation. Later on in the development of Project 9 there were further changes in the actual working of the organization. Most of these changes tended toward centering more of the work at Grand Isle, under the direct supervision of Dr. Mackin. During the most active period in 1947 and 1948 over 90 persons were employed on the project, and there were still 43 employees at the end. As the contract indicated, the possible effects of oil operations and the improvement of commercial oyster-growing were the phases of Project 9 given priority at the beginning. However, studies of parasites and disease had been mentioned in the tentative plans for the investigation proposed on February 18, 1947. Divisions of Bacteriology and Parasitology were included in the original organization. By the summer of 1948 it had become certain that a disease was causing a constant mortality of oysters during the warm months in Louisiana waters west of the Mississippi River. lt was increasingly evident that this disease was harmful to oyster production. The drilling operations, oil losses, and bleedwater effiuents which had been pointed out by local oystermen began to look very doubtful as causes of significant mortality. The protozoan Nematopsis and the boring worm Polydora were investigated as possible causes of disease in 1947 and 1948, but the organism that caused most of the mortality remained unknown. Bacteriological studies gave no promising leads. Studies of diseased tissues and blood of oysters in the summer and fall of 1948 showed that a yeast-like organism was present in most gapers. These were studied in live smears. Sectioning of diseased oysters by Mackin in December, 1948 revealed a tissue-damaging organism of unknown nature. After a long literature search by Hopkins it was tentatively identified on August 2, 1949, as a new DONOR'S COMMITTEE FACILITIES WM. E. LOOSE , CHAIRMAN HOUSTON 1 RESEARCH FOUNDATION ADMINISTRATION ------------< FISCAL 1 OR. A. A. JAKKULA, EXECUTIVE DIRECTOR COLLEGE STATION 1 DEPARTMENT OF BIOLOGY RESEARCH SUPERVISION DR. S.H. HOPKINS, DIRECTOR OR. J. G. MACK IN, ;,!~'::~:'0:•:~c'1.':"wo11ttc DR. C. C. OOAK, COORDINATOR ~---' LIBRARY 1 1DR. C. C. OOAKCOLLEGE STATION 1 1 D V S o N S o F R E S E A R C H 1 1 BACTERIOLOGY Olt. S.0. e1tOWN , CMIEP" 011. C. [ , 109Ell , CONSULTANT 1 1 1 BIOLOGICAL TECHINIQUE Olt, S. O. llllOWlll, CMll' 111.1. LOf'LAMO, ASSOCllT( 1 ] COl.Lf:G[ STATION 11 Glt.t.NO ISL[ 1 COLLU[ IT4TIO• OR . $.O. lllOWN 11 J.f . "1101C0" Ollt. S.11. lltOWN [ ,H. GlllONS E. C00,[lt 1 H.I. LOll'lANO T. TAYLOlt I'!: W. Wll,.H[lllf 1 CHEMISTRY Oll '· W. J[NSlfll, CHIH Olll.W. 1111. "0TTS, l.UOCIAT[ HCHNICAL COMMITT[[ CONSULTANTS ECOLOGY a HYDROBIOLOGY Olt, W, l . Hl!'.W&TT, CH1[, Olt.T. C. N[LSON, CONSUL.TAHT Olt. C. E. ZOll[LL., CONSULTANT Olt. C. lt. EL.SE T, COHSUL.TANT lt. W. CAlllT[lt l ,L, CH...ll[tllS W,lt, OUHKELHllQ J , [VANS H. K. MATT(ltSOH 1111. r, NAV[ltT O. M. fllEltlOI. W. T, flOLll G, O, flOOI. fl, ltlO[lt C. fl. ltTAN 1 GEOLOGY a OYSTER BIOLOGY HYOROGRAPHY Olt. J.CI. Mil.ClllN, CHll, lt. W. IUNl[L, t.SIOCIAT[ S. A. l.TNCH , CHI[, Olt. f,C, N[\.SON, CONSUL Til.NT H. A. MAltM[lt , COHSULTll.NT Olt. C. lt. ELSIT, CONSULTANT Olt , C. [ . ZOl(LL, CONSULTANT Olt, P. ll'OltltlNliA, CONIULTANT 1 1 1COL.LEO[ ST&TJON 11 WASHINCOTON o.e. ¡ 1 !~ ~:~~~$S[lf 11 JU. MAltMl:lt 1 '"""º 111.[ 0111 • .J. l . MACIUlll 111,W. lll[Nlll L. IOIWll.L J. CAltYllll .l.L. CANNAT[LL• T. C, NOSO.. J,lt.FINEOAN A.,f, CANNATCLLA, l. WALLS ft, L.A,L[Vlt CLUIC F. ... CAUTHllON W. 0 . WILSON J. I. IWING , "HOTOGltAPHlllt IU.• HAllllll,,.ILOT e.e. KlNT C. L. WUT C. lt. WlLOllil O.A, WlllAY 1 PARASITOLOGY Olt. V. Sflft&IU[, CHllP' Olt. J.H, ltOl[ltTS, ASSOCIAT[ 1 1 ISL[ ll[ltHOOL.E l'OST SCHllll.OUI SHAV[LY 1 011 . W. G. KEWATT ,OltT AltUISAS Olt. E.J. LUNO N.A, IACHWAL.0 Olt. l . SUNTIUI O. Kltl\M[lt [.H. flOWEl.L S.I. W[\.CH 1 PHYSIOLOGY Olt. ( ,J. L.UNO, CHl[P' Qll, Q, IUNTEll, &llOCIAT[ Ofl. T. C. NILION, COfllllUt.TAffT Olt. C.'l ELIET, CONIUL'Til.NT Olt. C. I. ZOHLL, COfrtSUl.TANT 11 COLL[li[ $TATION Olt. f: W. JENS[N Olt. W. M. ll'OTTS IHITltt.INUITATION A. L. fl<ltll.CI( Sl"f:CTllOSCOflT OltGAHIC CHOI. Ol'I. C.ll. HANCOCK W&TEJt. CHEM, P.J.'4. UL.LU l. HOOO , , O'llll[N M. Ol'[ltSTUIT M, WIL$0H '· WITTlG 1 Glt&NO J.O. H,W. [ ,H. [ ,S. F1c. l. Organization and personnel of Research Project 9 of the Texas A&M Research Foundation. Xl species of the fungus genus Dermocystidium Perez. This information was passed on to H. M. Owen and Albert Collier, who were independently studying the same disease. A description of the new species, Dermocystidium marinum, was published jointly by Mackin, Owen, and Collier in Science on March 31, 1950. Thus, after three years study, was accomplished the major objective of Project 9, the discovery of the cause of those mysterious oyster losses which were not due to any of the known lethal agencies such as storms, floods, or predators. But when Project 9 terminated on May 31, 1950, much of the epidemiology and pathology of the Dermocystidium disease remained unknown. Project 23, sponsored by the six companies that sponsored Project 9 plus the Gulf Refining Company, started on Junc 1, 1950. The new Department of Oceanography (now Oceanography and Meteorology) at the A & M College of Texas was designated as the research agency. Project 23 was described as "maintenance of the Marine Lab­oratory at Grand Isle," but continuation of the oyster disease study was its main purpose. The nucleus of the staff consisted of four men, but more were employed for special work when necessary. More than 400 reports and memoranda have resulted from the two oyster mortality projects. About 200 of these reportcd final results of researches; the rest were reports of trips, conferences, or the progrcss of ur.completed studies, and are of historical interest only. fottN G. MACKI'.'i AND SEWELL H . HoPKINS Studies on Oyster Mortality in Relation to Natura! Environments and to Oil Fields in Louisiana1 J. G. MACKIN 2 Department o/ Oceanography and Meteorology AND SEWELL H. HoPKINS Department o/ Biology Agricultura}, and Mechanical College o/ Texas College Station, Texas Table of Contents Page ABSTRACT --------------------------------------------------------------------------------------------------------------3 lNTRODUCTION ____-----------------------------------------------------------------------------------------------_____________ 3 Preliminary Studies and Definition of the Problem THE ÜYSTER lNDUSTRY IN LOUISIANA --------------------------------------------------------------------------7 The Natural Reefs Locations of the Natural Reefs Depletion of the Natura! Reefs Causes of Depletion of the Natural Reefs The Development of the Planting Industry Production Statistics Production in Jefferson Parish Compared with Production in the Louisiana Marsh State Shell Planting for Rehabilitation Purposes PHYSICAL AND CHEMICAL CoNDITIONs ------------------------------------------------------------------------21 Tides and Tidal Currents Oxygen, Redox Potential, and Hydrogen Sulphide in the Barataria Area Turbidity Water Temeprature Salinity Salinity of Barataria Bay and its Relation to Rainfall Salinities in Barataria Bay after Severa! Months of Rainfall Deficit Eff ect of the Mississippi River Salinity Gradients from East to W est in Barataria Bay Rising Salinity During the First Half of the 20th Century Biological Significance of Salinity 1 Oceanography and Meteorology Series from the Department of Oceanography and Mcteorology, the A & M College of Texas. A report from Project 23E, Texas A & M Research Foundation, spon­sored by Texaco Incorporated, Humble Oíl and Refining Company, The California Company, Gulf Refining Company, Phillips Petroleum Company, and Shell Oil Company. 2 Now Department of Biology, Agricultura! and Mechanical College of Texas. HYDROCARBONS IN Muns AND wATER --------------------------------------------------------------------------50 Methods of Sampling Possible Sources of Pollution Natural Hydrocarbons in Muds Origin of Hydrocarbons in Muds Hydrocarbons in Muds and Their Relation to Oyster Mortality Petroleum Hydrocarbons around Bleedwater Outlets Hydrocarbons in the Bottom Muds of Barataria Bay Hydrocarbons in Water Studies of Dilution of Bleedwater Calculations on Dilution of Pollutants Factors Affecting the Length of Time Crude Petroleum May Be Retained in an Area Bacteria] Oxidation of Hydrocarbons Rates of Oxidation of Louisiana Crude Oils Summary of Data on Hydrocarbons EXPERIMENTATION WITH ÜIL AND BLEEDWATER --------------------------------------------------------82 Research Foundation Studies of the Effed of Oil on Oysters Normal Rates of Mortality in Louisiana Oysters Laboratory and Field Studies of the Effect of Crude Petroleum on Oysters Physiological Studies of the Effect of Crude Petroleum on Oysters Studies of the Effects of Oil Field Bleedwater on Oysters Physiological Effects of Bleedwater Studies on the Effect of Bleedwater on Mortality of Oysters in the Bay Ste. Elaine Oil Field Experiments to Test the Effect on Oysters of Bleedwater Produced in the Lake Barre Oil Field Summary of the Bleedwater Studies at Lake Barre Experiments Testing the Effect of Bleedwater Effiuents of the Caillou Island Oil Field on Oysters Experimentation on the Effect of Bleedwater on Oysters at the Dog Lake Oíl Field Experimentation on the Effect of Bleedwater on Oysters at the Lake Pelto Oil Field Growth of Oysters Subjected to Crude Petroleum Growth of Oysters Near Bleedwater Discharge Sites Studies of Accidental Losses of Oil Studies on Glycogen in Oysters Treated with Oil and Bleedwa,ter Studies on the Effect of Natural Gas from Deep Wells on Mortality, Growth, and Glycogen Content of Oysters Experiments with Components of Drilling Mud Studies of Seismographing and Its Effect on Oysters Studies by the Research Foundation SuMMARY AND CoNCLUSIONs ---------------------------------------------------------------------------------------124 LITERATURE CITED ----------------------------------------------------------------------------------------------. ---... -. . 126 Abstract Field and laboratory studies and examination of historical records were made in the tidal waters of Louisiana to determine the possible role of operations of oil companies on mortality of commercial oysters, Crassostrea virginica. Periods of disastrously high mortality were found in past records, both before and after the beginning of oil operations in the area. According to official figures, 1940-1947 as a whole was a period of good production, but there was a decline in 1944-1947 due mainly to a sharp drop in St. Bernard Parish, outside the area of major oil operations. Field studies showed that oysters had a consistently high mortality rate throughout the warmer half of the year in the study area, and that mortality rate increased with salinity increase within this area. There was no such correlation with proximity of oil fields. Chemical studies revealed measurable quantities (0.001 to 0.010 percent dry weight) of un· saponifiable carbon tetrachloride extractives, called "hydrocarbons" by sorne chemists, in ali mud samples tested, including many from locations where no pollution seemed possible. In sorne cases the quantity oí such materials was correlated with the amount of plant debris in samples, and it was found that unsaponifiahle material could be extracted by carbon tetrachloride directly from plants in areas distant from any source of petroleum. Within oil fields, the amounts of unsaponifiable carbon tetrachloride extractives were highest (up to 5.8 percent) in mud samples taken near bleedwater outlets and other known centers of pollution, and were correlated with high ( up to 0.00578 percent) "pentane and heavier hydrocarbons" as measured independently by a commercial laboratory. Water samples showed minute quantities (approximately 1 ppm) of substances identifiable by routine analysis as "hydrocarbons" to be very widely distributed in Louisiana hay waters. These suhstances showed highest concentrations (up to 226 ppm) in oil field bleedwater and were still high (up to 7.6 ppm) in hay or bayou waters near the point of discharge, but decreased rapidly with distance from the source. "Hydrocarbon" content of mud and water was no higher in areas of high oyster mortality than in areas of low mortality. Calculations showed that bleedwater alone could not significantly increase the hydrocarbon content of mud or water on the commercial oyster heds where mortality occurred even if none were destroyed. Bacteriological studies showed that crude oil and its fractions were rapidly destroyed by bacteria living in Louisiana hay muds. Accidental oil spillages were found to cause enough oily taste to make nearby oysters unpalatahle for periods ranging from severa! days to severa! weeks, but did not kili any oysters on commercial beds. In one case, however, a few intertidal oysters were killed by smothering. Lahoratory experiments showed that bleedwater, crude oil, water extracts or emulsions of crude oil, and the principal constituent of drilling mud (barium sulphate) had no effect on survival of oysters over periods of severa! months, when :he concentrations tested were far above the maximum that could be maintained on an oyster bed. Quebracho, another constituent of drilling mud, caused sorne increase in mortality when used in concentrations much higher than could occur on an oyster bed. In phvsiological experiments, bleedwater and water extracts of crude oil slowed water pumping and filtering rates of oysters when used at concentrations much higher than could be expected in oyster­growing waters, but these effects were temporary and reversible. In field experiments, spraying oysters repeatedly with crude oil and keeping them under a surface !ayer of crude oil did not affect survival or growth overa period of months. In other field experiments oysters were kept for months at various distances from bleedwater outlets, underwater natural gas discharges, and other sources of pollution. A discharge of 6600 barreis of bleedwater per day at Lake Barre increased mortality of oysters as far as 50 to 75 feet from the point of discharge, and apparently caused decrease of shell growth and glycogen storage in oysters as far as 150 feet away, but had no detectable effect at greater distances. Field experiments at Dog Lake, Caillou Island, Lake Pelto, . and Bay Sainte Elaine oil fields did not show any adverse effect of bleedwater, natural gas, or small oil spillages upon the setting, survival, growth, or fattening of oysters. High explosives used for seismographic exploration in the manner prescribed by Louisiana law did not injure oysters either immediately or overa period of months. lt was concluded that oil production factors of the kinds tested could not be responsible for the oyster mortalities spread throughout the large area whe.re damage was claimed. The widesprearl mortalities that did occur during the study period were correlated with high temperature and high salinity, hut not with proximity to oil operations. lntroduction Projects 9 and 23 of the Texas A & M Research Foundation were aimed at deter· mining the cause or causes of mortality of oysters on the Gulf Coast, especially in Louisiana and especially during the period beginning in 1940, when the oyster growers' claims of abnormal mortality began. This paper summarizes researches and findings on the Louisiana oyster industry and its history, the environmental conditions in the area where oyster mortality was claimed, and the interrelationships of the oil and oyster industries in that area. It is a summary, not an attempt to present complete data; it organizes, in a condensed form, data from a large number of separate reports that bear on one question: Has pollution by oil or oil well effiuents, or seismographic explora­tion, caused mortality of oysters in Louisiana? For acknowledgment and an account of proj ect administration (Fig. 1) see the preface to this volume. PRELIMINARY STUDIES AND DEFI'.'IITIO~ OF THE PROBLEM The Research Foundation undertook (1) to determine whether or not mortalities of oysters in Louisiana were excessive, (2) to determine if mortality of oysters of con­siderable extent had occurred or was occurring, to determine the causes of the losses, and (3) if oil operations were responsible for any part of the mortalities, to determine what was to be done about it. It was noted that recent accounts assumed that oyster mortalities were something new, and that the industry in Louisiana had previously been in a continuous state of good health. For this reason it was deemed wise to consult as many historical records as were available. The early records of the various state commissions having to do with oysters from the inception of state or parish supervision were found to be good sources of information. In a later section, data on oyster mortality from these historical sources are more fully detailed. Here suffice it to say that the record was puzzling in the extreme, for there appeared to be few periods within written history when the oyster industry was not in trouble. State production records show that there was no decline below the average in production at the time of alleged mortalities. The earliest records showed a steady decline in number of producing natural reefs, with here and there relatively catastrophic and rapid periods of decline during which production in whole areas was greatly reduced. Sorne of this loss occurred prior to 1900, but much was in the period from 1900 to 1920. In this period were witnessed severa] major attempts to rehabilitate an industry which considered itself in deep trouble at this early date. First the Gulf Biologic Station was established and devoted most of its efforts in its short life time (from 1902 to 1910) to detailed studies of the oyster industry and its troubles. In the same period the U. S. Bureau of Fisheries was sufficiently interested to send H. F. Moore (in 1898) and later Moore and T. E. B. Pope (in 1906-1908) to study means of developing a planting industry and to work out methods of rehabilitation of the moribund Barataria Bay industry. As the century progressed a clearer picture of the situation began to take shape in published reports on the Louisiana oyster industry. First, it was apparent that depletion of natural reefs and the later troubles of the planted beds were associated primarily with high salinity of the oyster-producing waters. The occasional heavy losses to crevasses (Gunter, 1949) were well understood and these floods often did as much good as harm to the industry. But the unexplained losses were in nearly all cases associated with en­croachment of Gulf waters carrying high salinities. Second, the mortality waves were associated with high water temperature. Even when mortalities occurred in winter, they were asrnciated with unseasonable warm weather. Third, the mortality waves were selective of older oysters, and those used for counter stock were most affected. This is only another way of saying that mortality rates increase with age of the adult oyster. There was an apparent difference in death rates of seed oysters and those which had been on the bed for a year or more, the latter having a much higher mortality. Fourth, the mortalities affecting oysters did not extend to the community of animals associated with them on the beds. Vigorously developing communities were reported on beds where 50 to 90 percent of the oysters died. Certain data were compiled for the purpose of determining when and where mor­talities occurred in the 1940 to 1947 period. These included (1) the locality of greatest alleged losses as indicated by the location of leases on which claims were filed and the amount of damages claimed, and (2) the period of greatest losses as indicated by the year for which claims were made. The data are contained in Tables 1 and 3. A summary of the data which are presented in Table 1 shows that the damages were said to begin in 1940-41 with a quite modest total of less than $10,000 in claims. TABLE 'l Claims for each of the years 1940 to 1948 in percent of the total $32,831,079 ( 1940-48 ) Year Percenl of total 1940-41 1941-42 1942-43 1943-44 1944-45 1945--46 1946--47 1947-48 0.03 1.59 2.18 4.95 !i.69 28.47 55.53 1.57 TABLE 2 Estimated value of total recorded oyster crop for Louisiana 1920-'1949 at $5.00 per barrel*,t 1920-2,115,560 1921_.:2,204,160 1922-2,153,860 1923-2,666,655 1924-3,898,030 1925-3,365,645 1926_.:3,372,515 1927-3,791,115 1928-2,483,705 1929-3,858,170 1930-3;230,770 1931-2,192,310 1932-2,'157,680 1933-3,084,080 1934-4,716,040 1935-3,5'22,030 1936--3,838,485 1937-5,435,880 1938-2,880,250 1939-4,324,370 1940-5,407,290 1941-4,889,035 1942-5,894,800 19~5,389,325 1944-3,171,510 1945-3,142,145 1946--3,105,650 1947-3,306,295 1948-3,482,005 1949-4,133,700 *This estímate is admilledly much loo high for most of the period of the table. It is used throughout to preserve unifo1·mity. t A Louisiana barrel is approximately 3.7 cubic feet and 0.106 cubic mcters. TABLE 3 Percent of claimed losses of oysters in different sectors of the Louisiana oyster-producing area Total amount claimed was $32,831,079 St. Bemard Parish Placr¡uemines, Eof Miss. R. W. ol Miss. R. & E ol Grand Bayou Creater Baralaria Bay Tirnbalier, Terrebonne Bay Wof Terrebonne Bay Zero 3.0 16.0 67.0 14.0 Zero NOTE: Because of the manner of filing the claims9 the exacl percentages belonging to each area could not be ascertained. The figures are approximale only. In the year 1946--47 the claims reached their apex at over $18,000,000 or 55.5 percent of the total. lt was clear that it was thought that there were catastrophic losses in the period 1945 to 1947 inclusive. A comparison of the dollar amounts with the estimated mean yearly value of the total Louisiana crop from 1920 to 1949 shows that the claims for the fiscal year 1945-46 totaled more than twice the mean, and the claims for 1946-47 were about four times the mean (Table 2). lt was noted that according to Louisiana production statistics, the period from 1940 to 1947 did not produce less than the mean for all of the years, and the period from 1940 to 1943 had production sig­nificantly greater than the mean for the thirty years included in the table. Not all of the claims were for dead oysters. Damage to leases was also alleged but the comparative amounts of such losses were not generally stated. The petitions pinpointed Barataria Bay, including its contiguous satellite bays and bayous, as the locale of the biggest part of the claimed losses. In Table 3 is a breakdown by areas, showing percentage of claimed losses in each. With 67 percent of the alleged losses in the Barataria basin, there was little trouble in deciding where to concentrate the efforts aimed at solution of the oyster mortality problem. The views of oystermen were of importance in shaping the direction of researches. The Research Foundation made a study of the opinions of oystermen scattered through­out the area where heavy mortality was said to be a recurring annual event. In 1947, S. H. Hopkins interviewed 10 oystermen for opinions as to the causes of the mor­talities, of whom four thought the operations of the oil companies were responsible for mortalities. Others made explanations which involved only natural causes. Earlier Galtsoff (1942) had reported on a similar survey by Kavanaugh made in October, 1941. Kavanaugh talked to 13 oystermen, of whom two thought that pollution was one cause of the troubles. One of these named oil as the polluting agency. The other named both oil and sulphur bleedwater. Both named natural causes as responsible for part of the mortalities. Seven out of the 13 named natural causes; the others had no opinion on the losses. Of the natural causes given, high salinity was most often named. Conchs, bad water, "sick" seed, and lack of care in planting were also mentioned. Chipman ( 1942) found only isolated cases of excessive mortality in the "high mortality" area of Louisiana in the summer of 1942. He concluded that one of these (in Bastian Bay) was caused by conches, but pointed out that conchs were nota problem in most oyster-growing sections. The other mortalities that he found were in Bayou Cholas and Bayou St. Denis. A. E. Hopkins, representing the U. S. Fish and Wildlife Service, together with Louisiana officials, and representatives of the oyster and oil industries, made a survey of beds in the area from about Scofield Bay to Barataria Bay. This trip was in the period from February 11 to 15, 1947. Hopkins circulated a small memorandum of the findings. He found evidence of extensive losses of oysters. In his notes, he observed that the normal community of the oyster beds seemed to be unimpaired. Certain facts of value emerged from the early interviews with oystermen. First, it was apparent that no one knew what was causing the alleged unusual mortalities. Second, it was evident that most of the trouble was in the Barataria Bay area, and third, that the greatest losses were believed to have occurred in the 1945-1947 period. Because of the great variety of opinion, it became necessary to study numerous individual sub-problems. The Oyster Industry in Louisiana A history of the oyster industry in Louisiana is a recital of trials and tribulations. The earliest researches (Moore, 1899; Zacherie, 1898; Cary, 1907a; Cage, 1904), and the latest (Owen, 1955; St. Amant, 1955; St. Amant et al., 1956) were undertaken because of ills, imagined and actual, which beset the oyster industry. The earliest troubles stemmed from a steadily increasing impoverishment of the natural reefs, on which the industry was based. Overfishing, according to early writers, was the prime cause of the failure of the natural reefs. It is believed, for reasons to be discussed later, that this was not the only reason for impoverishment of the reefs, but there can be little doubt that in sorne areas fishing pressure was intense. In about 1886 (Moore, 1899) enterprising individuals began to make attempts at oyster culture, near the end of the Mississippi River delta. The seed carne from Garden Island Bay, also at the end of the delta. Other plantings were made in the area of the "Salt Works" below Quarantine Bay, east of the Mississippi River. As more bottom was made available to oystermen for planting purposes, the industry shifted its emphasis from tonging the natural reefs to extensive planting. Since the natural reef,s became largely seed reefs under the new regime, the natural reef system never lost its importance, and natural reefs for the production of seed remain the back­bone of the industry. But the plantings themselves developed troubles, basically the same as those which affiicted the seed reefs, with one difference. A planting cannot be "depleted," so depletion became recognized as mortality. The real planting period began about 1902 to 1904, when extensive holding of leased bottom was provided for by legis­lation. For a few years after 1904 the oystermen were allowed to use dredges for taking seed from state-operated reefs, and the general picture was one of a developing, vigorous industry based on seed planting and continued use of the natural reefs. The following sections give a more detailed account of the production based on the natural reefs and on the later seed and shell planting. Information is based on published accounts of re­searches and the semi-annual reports of the various state agencies having to do with the oystet bottoms. THE NATURAL REEFS H. F. Moore (1899) made the first survey of the natural reefs of Louisiana, but failed to estímate the acreage involved. He found extensive natural reefs, as well as many extinct reefs, all the way from the Louisiana Marsh to Atchafalaya Bay. Moore suggested that a natural reef should be defined as follows: "A natural oyster reef, bar, or bed is an area of not less than 500 square yards of the bottom of any body of water upon which oysters are found or have been found within a term of five years-in quantities which would warrant taking them for profit by means of tongs." The dimensions of such a natural reef might be 50 by 10 yards and the area only about 1/ 10 acre. Moore's definition anticipated the time when leasing on a large scale would begin, and decisions would have to be made as to whether a section of bottom was available for leasing. Payne (1912) made a hurried survey of the natural reefs in the fall of 1910. He found a total of 62,740 acres which presumably carne within Moore's definition. Most of this (53,200 acres) was in Sister Lake, Bay Junop, and the Point Au Fer reef in Atchafalaya Bay, which probably included Marsh lsland reef. This left a small amount for the Louisiana Marsh (3,040 acres) , and for California and Quarantine Bays ( 6,000 acres), and left none for Barataria Bay, Timbalier Bay, and Terrebonne Bay, the area west of Terrebonne Bay to Sister Lake, or any satellite bays or bayous. It seems clear that Payne ignored vast areas of low grade coon oysters and all areas of sparse growth. Since he was mainly interested in developing a planting industry, it served his purpose to reserve these areas for priva te leasing. Cary (I907b), just four years prior to Payne's survey, had studied ali of the natural reefs from Sister Lake to Raccourci, including Terrebonne Bay and contiguous waters, and had found extensive natural reefs. Also, McConnell ( 1932) stated that there were 50,000 acres of natural reefs east of the Mississippi River in St. Bernard and Placquemines Parishes. While this may be an overstatement, it is probably a much better estímate than was Payne's "survey" of 9000 acres. There has never been a real survey of Louisiana's natural oyster reefs and no one will ever know how extensive was the resource prior to the construction of the Mississippi levees. Before the tum of the century (Moore, 1899), bays Iike Barataria and Terre­bonne reportedly contained only relict reefa. The estimates of Payne and McConnell were made after Cates !1910) had declared that natural reefs were a thing of the past. This certainly was not true either, as is proved by the present phenomenal production of the Placquemines seed reefs in California, Quarantine, Black, and other bays. But the lack of agreement shows that no one ever really knew the magnitude of the resource. LocATIONS OF THE NATURAL REEFS Ali of the Louisiana saline marshes support natural growths of oysters. Most of these are patches of coon oysters, sorne small, sorne large. In high salinity areas these patches are apt to be intertidal, and are almost always in the bayous and small bays. Many are in marsh ponds only narrowly connected by tidal runs to the larger bays. In waters of lower salinity the natural oyster beds are subtidal, and may be in the bottom of deep scoured bayous. Most often these small oyster beds are developed on the old Rangia beds; such a bed may produce both oysters and clams in scanty numbers. Generally, by the "natural" reefs, authors mean those of large extent, in large bodies of water. At present these exist in the following areas: ( 1) In Mississippi Sound north of the Louisiana Marsh and in the Louisiana Marsh proper there are still many extensi.ve natural reefs. Most of these at present have only thinly scattered oysters and many do not qualify for the name of reef, since there is no solid shell substrate. (2) In the area _from Mozambique Point to California Point, east of the Mississippi River in California, American, Quarantine and Black Bay, and in sorne others there are actual hard reefs. They are highly productive, but have not always been so. They are dredged for seed annually, and many are almost literally Ieft stripped. Culling is not practiced and the reefs take the hardest abuse imaginable. In spite of this rough treat­ment they rebound in a very short time. At present they provide most of the seed used by Louisiana planters. ( 3) At the end of the Mississippi River delta there are severa! small bays with very low salinity into which the Mississippi pours huge quantities of water in flood periods. Under the predominantly fresh surface water, tongues of salty Gulf water push in along the bottom and maintain small hard reefs in these exposed bays. These are economically insignificant, but of great biological interest. ( 4) W estward from the Mississippi as far west as Dog Lake and Hackberry Bay there are innumerable srnall natural reefs. Most of these are individually unimportant but in the aggregate they produce many fine oysters. Nearly all are in the bayous and small bays to the north of the main water bodies. They can exist only in those water bodies that are periodically flushed by local freshets. This flushing reduces both conchs and fungus disease to low levels and thus increases longevity of the oysters so that they reach market maturity in satisfactory quantities. Much planting is done in the same small water bodies, using the local seed. (5) In Sister Lake, Bay Junop, and the neighboring bays there were once major natural reefs. These have been nursed along by the Division of Water Bottoms and still contribute respectable quantities of the seed oysters used in areas too far west to depend on the reefs east of the Mississippi. In late years (St. Amant, 1955, St. Amant et al., 1956) Sister Lake, because of increasing salinity, has largely broken down as a natural producing area. (6) In Atchafalaya Bay, the Point Au Fer reef, the largest in Louisiana, is con­tinuous on the far west with the Marsh lsland reefs. A large part of the Point Au Fer reef is now dead because of increasing flow of fresh water from the Atchafalaya River. For sorne years it has been mined for shell. The western end still has live oysters and the Marsh Island reef has produced seed of an inferior sort for many years. Most of the Atchafalaya reefs are massive, solid, and stand high above the surrounding bottom. They are useless for oyster production but are valuable as a source of basic information. (7) In Vermilion Bay and others to the west of Atchafalaya Bay, there are inter­mittent reefs all the way to the Sabine River. The Vermilion Bay reefs in recent years have shown signs of developing into an economic asset but do not compare with the producing areas farther east. DEPLETION OF THE NATURAL REEFS Moore ( 1899) was the first to publish data on the decline of production of the natural reefs of Louisiana. His mission in Louisiana was evidently to develop sufficient knowl­edge of quantities of oysters available, oystering methods, and basic ills to advise the Legislature in framing oyster law. The emphasis placed by Moore on the declining natural reef production and the desirability of developing a healthy planting industry shows that his chief concern was the apparent failure of the natural reefs to meet the needs of an expanding industry. Cage ( 1904) described the oyster industry of the period prior to 1870. According to him, depletion of the natural reefs was far advanced prior to that date. He stated that the reefs in Placquemines Parish were "exterminated" first, which led the oystermen from there to invade the more westerly Parishes where the reefs were "little used." They apparently used the reefs in Barataria, Timbalier, and Terrebonne bays for obtaining seed, planting the oysters in the Placquemines beds. Barataria reefs followed the Placquemines route to depletion, and in turn those in Timbalier Bay and Terrebonne Bay. Dymond (1904) stated that he knew of "hundreds of natural reefs that have been completely wiped out," but he failed to point out the locations. lt is assumed that he had in mind the Placquemines and Jefferson Parish reefs. In 1906 the oyster commission of Louisiana reported that natural (seed) reefs east of the Mississippi in Placquemines Parish had suffered because of extensions of the levee system on that side. It was also stated that because of lack of food, the oysters had for two years been very poor. This is probably the first report that coupled increased salinity, resulting from the levee system, with depletion of oyster reefs. Baylor (1904) had advocated extensions of the levee system as a means of protecting oysters from destruction by fresh water. By way of contrast, Breaux et al. (1908) in the oyster commission report for 1906 to 1908 stated that "lt cannot be said that the natural oyster reefs of this state are in danger of depletion." Cary ( 1907b) made an extensive study of oyster reefs in Terrebonne Parish, from Sister Lake eastward to Lake Raccourci. He listed 32 bays and bayous in which he found depleted natural reefs; many of these had no oysters on them at ali. Moore (1899) had briefly surveyed this same region, and Cary pointed out severa! dead or dying reefs which Moore had named as good producers eight years earlier. Gates (1910) stated that nearly ali natural reefs in Louisiana were then depleted, which was obviously an overstatement. Gates was in favor of leasing all natural reefs, even if they were producing, which probably explains his exaggeration. It was in 1910 that Payne (1912) surveyed the natural reefs and carne up with his figure of 62,740 acres. Payne (1914) reported that the natural reefs of St. Bernard Parish (the Louisiana Marsh) were depleted and that sorne of these had been leased for planting purposes. A most important loss to the industry was reported by Payne (1914). In 1904 Bayou Lafourche, an important distributary of the Mississippi, was severed from the river. Formerly, it fed fresh water to the important seed reefs of the northeast part of Timbalier Bay. As a result of increasing salinity following closure of the bayou, these reefs deteriorated badly. They are not dead at the present date, but production is marginal and unpredictable. There are subsequent references to decline in production of the natural reefs of Louisiana, but most of them do not distinguish between planted beds and natural reefs. Statements of early authors showed clearly that a serious decline had occurred over large areas, and just as clearly that the natural growth of oysters was prolific in many other areas. As reefs disappeared, usually in high salinity areas, new ones appeared in lower salinity areas and, as Payne (1912) remarked, the industry appeared to be moving inland. CAUSES OF DEPLETION OF THE NATURAL REEFS Moore (1899) believed that the destruction of the natural reefs was due to over­fishing coupled with failure to cull out and return shells and young oysters to the reefs. Cage ( l 9Ó4) thought that failure to observe spawning seasons and failure to cull were responsible for destruction of the reefs. Cary (1906, 1907a) thought that local freshets, boring sponges, conchs, and overfishing were causes of depletion. Moore and Pope (1910) made experimental plantings which were successful in low salinity waters but uniformly failures in high salinity areas. Payne ( 1912) blamed destruction of reefs in Caminada and Timbalier Bays on closure of Bayou Lafourche, and overfishing for de­pletion of reefs in Bay Junop and Sister Lake. He later ( 1920) attributed the decline of reefs in Placquemines east of the Mississippi to high salinity, and the destruction of Barataria reefs to the same factor. It is difficult to agree that overfishing was the major cause of depletion in the early years of the industry. First, only tongs were used for taking oysters, and it is not believed to be commercially feasible to tong a reef to the point of biological extinction. The production recorded before the turn of the century was not great enough to make serious inroads on the natural supply. If Payne was right in his survey, and there were 12,720 acres of natural reef (not counting Point au Fer), a rough estímate of fishing pressure can be made. According to Gunter ( 1949) the average annual production of oysters between 1880 and 1900 was about 236,000 barrels. The acreage of the natural reefs must have heen much greater in 1880 than Payne's 1910 survey showed, and it is estimated that it was probably twice as great. If that is true there were about 25,000 acres of natural reef to begin with, which were being worked at an annual rate of 236,000 barreis in the 20-year period from 1880 to 1900. Each acre therefore produced less than 10 barrels annually. This is not a great fishing pressure, especially in view of the fact that even prior to 1900 sorne of the production was from shell plantings. On the other hand, the observed correlations of high salinity and depletion appear to present at least a workable hypothesis. High s~linity in itself is not detrimental to oysters, as numerous studies have shown. Oysters in Louisiana grow faster, spawn more pro­lifically, and set in larger numbers in high salinity waters, up to oceanic salinity con­centrations, than they do in low salinities; but competition, predation, and disease impose a high annual death rate on both immature and mature oysters in highly saline waters. Rises in salinity paralleled the construction of more efficient and more extensive levees along the lower Mississippi River (Gunter, 1952). The higher and more stable salinity made the oyster beds more favorable habitats for other organisms, including competitors, predators, parasites, and other enemies, and therefore less favorable for oysters. Hence the increase in oyster mortality accompanying the increase in salinity. THE DEVELOPMENT OF THE PLANTING bDUSTRY The beginning of the planting system in Louisiana occurred in the period between the end of the Civil W ar and 1885. Oystermen bedded oysters, which they took from the natural reefs, on limited areas of hard bottom near their camps. They had no lease or title to these "bedding grounds." Bedding of oysters did not mean planting for growth or cultivation in any modern sense. Oyster5 tonged from the natural reefs were piled on a limited area of clean shell bottom, so that they could be quickly reloaded to take to market when a boatload was accumulated. lt is not certain just when this practice developed into a true planting system. Moore (1899) gives credit for pioneering in oyster cultivation to Louis Esponger, who planted seed in Whale Bay in 1885. The seed for this planting carne from Garden Island Bay. Both bays were at the extreme end of the Mississippi Delta, and both are now silted into deltaic plain. Esponger's effort may have been preceded by efforts of others who planted in the area called the Salt Works, just to the south and east of Quarantine Bay on the east of the Mississippi. At one time, these plantings, added to production from natural reefs in the Louisiana Marsh, supplied most of the New Orleans trade. It appears certain that planting first developed in Placquemines Parish, where the natural reefs were first depleted. The Louisiana Legislature first made bottom available for lease in 1886, but the amount was only three acres per person. lt seems that this amount was made available only to allow oystermen to control their holding or "hedding" grounds to prevent theft of their oysters while they completed their loads. In 1892, the amount availahle for lease was increased to ten acres. By leasing in the name of relatives oystermen could accumu­late sufficient acreage of hottom to permit actual planting, and it is helieved that the first real impetus to planting shell as well as seed developed in the period from 1892 to 1902. In this latter year the allowahle holding per person was increased to 20 acres and in 1904 the limit was extended to permit one individual or corporation to hold 1000 acres. This is the limit toda y. According to Moore (1899) the first "plantings" were made on areas as small as 50 feet square and oysters were piled as much as a foot deep on the hottom. This ohviously was not planting hut a step in marketing. It is interesting that this is still a method in wide use in Louisiana, and is sometimes costly to the oystennan. Moore also descrihed planting of culch in Placquemines Parish. Shell or other culch was planted in shallow water from a few inches to 18 inches maximum depth and along the shores of hays and bayous. Louisiana hays and bayous are usually very soft in the middle, while the margins are of stiff mud supported by heavy concentrations of partially decayed plant materials derived from the marsh. Y oung oysters caught on culch along the margins were culled out at the end of the year and planted in deeper water as singles. As seed they were crowded and · of typical coon oyster type, but after culling they quickly developed good shape and size. Louisiana oysters at that time, as at present, grew well in salinities lower than the lowest in which oysters could survive in more northern dimes (Moore, 1899; Mackin, 1956a) . This is in agreement with the theory that marine organisms extend their ranges into lower salinity in wann countries (Hesse, Allee and Schmidt, 1937). But even at that time most oyster leases were in high salinity areas, as evidenced by the trouble with conchs. Moore ( 1899) estimated that in 1898 there were 500 oystermen operating in the area between Bay Jacque and Bastian Bay. Most of these planted oysters, for Moore remarked that the natural beds of Placquemines Parish west of the river were "limited in extent and of but little importance." Oystennen planted 600 to 800 sacks of seed oysters per acre of bottom and, according to Moore, sometimes harvested two sacks for one at the end of a year. Two years from setting time sufficed to mature oysters for market. A lesser planting area was developed in northeast Timbalier Bay, using the seed growing in the same area. There was no estimate of numher of men engaged in this industry. Farther west in Terrebonne Bay and westward to the Atchafalaya about 32 oystennen were engaged in planting, a relatiwly small number for this very large area. Dymond (1904) summed up the planting industry from its beginning to 1902. In ali the period prior to that time 512 leases had heen taken out by oystermen, totaling 2820 acres. The average size of these leases was 5.5 acres, suggesting that most oysters "planted" were only held for marketing. In 1904 a rapid expansion began when the leasing of 1000 acres was permitted and the number of leases increased to 1194 with an average size of 19.5 acres. The total acreage increased in two years from 2820 to 21,853. Although the leased area increased nearly 700 percent, the production from 1903 (reflecting 1902 planting) to 1905 (reflecting 1904 planting) increased only 42 percent. This was because most production still carne frorn natural reefs. As late as 1908 the oyster commission reported that more than half of ali production was still from natural state-owned reefs. In 1907 total production was 933,960 barreis. If we assume that about 40 percent of this was from plantings, 374,000 barreis were produced from about 22,000 acres of bottom which is an average per acre of 17 barreis. Leasing for subsequent years varied from about 13,000 acres in 1935 to 48,000 acres in 1957. During the period of the multi-million dollar suits against the oil com­panies from 1940 to 1947 the leased acreage for oyster planting rose steadily from 14,749 to 23,279. The Auctuations in leased acreage for Louisiana are contained in the graph, Fig. 2. After the planting system was established the year of smallest production was in 1920 ( see Fig. 3), in which year there were under lease about 20,000 acres of bottom. The year of the greatest production was 1942 and in this year the acreage under lease was only about 16,000 acres. The recorded figures show no close relation between acreage under lease and total production. In the years from the end of the depression in about 1939 to the present, acreage under lease has generally increased. In the last year here recorded (1957) there were about 48,000 acres under lease. As far back as 1912 the Board of Commissioners for the Protection of Birds, Game and Fish (see Miller, Grace and Dodson, 1912) esti­mated that there were about 472,000 acres of good bottom in Louisiana. If this is a correct estimate Louisiana planters have never utilized more than about 10 percent of the available good bottom. Our own experience indicates that 472,000 acres was a gross overestimate. Many oystermen in Louisiana plant on bottom too soft or otherwise unfit for oyster culture. This was true as far back as 1898 (Moore, 1899). The writers believe that much of the bottom used in the early part of the planting era is now worthless, because of deterioration of the bottom or increased salinity of the water, and that oystermen have shifted most of their planting to new bottoms formed by the natural disintegration of shorelines. As the planting industry developed and production from natural reefs decreased two trends became apparent. One was the trend toward planting more seed and less shell. Louisiana oystermen in the early days of planting used both the seed planting and the shell planting methods. Although the shell planting method was said to be highly suc­cessful in the early part of the century, it nevertheless was largely abandoned in later years and a decided preference was given to seed planting. Shell planting by oystermen is still done but is now a relatively unimportant part of the industry, and has been so for many years except the plantings of shell in the Louisiana Marsh by the canning industry. Emphasis on seed planting has always thrown a heavy strain on the seed reefs and ha>. re­quired an increasing amount of shell planting for "rehabilitation" purposes. Originally rehabilitation was a correct word to use. More recently the State has taken over the function of planting shells on barren bottom. These shells are not for either maintenance or development of permanent seed reefs. When oysters attached to the culch are nearly large enough for market, they may be dredged by the oystermen from the State "seed" reservations, transplanted to the oystermen's leases, and shortly thereafter dredged for market. Thus much of the responsibility for success in oyster culture is now the State's, and the cost of all failures falls to the State. The other trend has been toward short-term planting methods. As early as 1920 (Payne, 1920), seed oysters planted in Barataria Bay were kept on the beds foras short a period as three to four months. McConnell ( 1932) also mentioned that oysters were kept on the beds only six months as early as 1932. This applied to large seed, small seed being left for a year. The short period usually was designed to include only cool months, o z "' 2i :! ,,... ,,... ,,. " " "' ~~ !!? ""' ~ YEA RS ~ F1G. 2. Fluctuations in acreage leased for oyster planting in Louisiana, 1902-1957. Shaded area includes years in which pollution damage was claimed. <ñ 1200 o z 150 "'~ o 1­ N "' ~ 120 z Q 1­ u ::> o o 90 o::: o.. "'­ o 1­ z 60 u "" o::: o.. "' 30 Ci?/ST BERNARD PARISH \ 1 1 1 1 . ~JEFFERSON PARISH MEAN PROOUCTION 1 1 r ,,,,_ ,,,, "ºº,_, \ ----------~------­ 1 1 1 \ \ 1 1 \ 1 1 ~' '', "t:>--­ F......--'t:>---1?/' 1940 41 42 43 44 45 46 47 48 49 1950 51 52 53 54 YEARS Frc. 4. Oyster production in St. Bernard Parish as cornpared with Jefferson Parish, 1940 to 1953. TABLE 5 Summary of shell and seed plantings for production of seed oysters in Louisiana Amount planled Year Localion barreis May 1917 Sister Lake 16,238 Aug.1917 Cabbage Reef 5,975 1917(?) Not stated 137,114 July 1919 Not stated 1,200 May 1929 Mississippi Sound ; Turkey Bayou 60,000 May, June 1930 Bay Boudreaux; Fox Bay 45,000 Spring 1931 Fox Bay 35,000 1932 (?) Quarantine 15,000 1933 (?) Bay Boudreaux 55,000 Spring 1934 Nigger Point 75,000 1935 Quarantine Bay 20,000 1936-37 Not stated 150,000 1938 '\1ississippi Sound; Half Moon Island 34,020 Spring 1939 Mississippi Sound; Half Moon Island 58,711 Summer 1941 Sister Lake 50,000 Spring 1941 Mississippi Sound; Half Moon Island 70,000 Summer 1943 West of Mississippi R. ; Sister Lake 91,632 1943 (?) East of Miss. River? 56,632 1943 (?) East of Miss. River? 7,270 Summer 1944 Sister Lake 29,185 Summer 1944 Lake Felicity 29,022 Summer 1945 Bay DuChene 15,251 Summer 1945 Lake Tambour 16,383 Summer 1945 Siste" Lake 19,825 Spring 1945 Bay Boudreaux 40,965 Summer 1946 Bay DuChene 20,048 Summer 1946 Sister Lake 19,213 Summer 1946 Bay Boudreaux 40,000 1948 Mississippi Sound; West of 3-mile Bayo u 19,014 1948 Bell Pass (seed) 10,618 1949 Sister Lake 21,560 1949 Lake Felicity 17,539 1949 Mississippi Sound; Turkey Bayou 14,314 1949 Bayou LaMer (seed) 8,255 1950 Sister Lake 34,620 1950 Lake Felicity 17,042 1950 Bay Gardene (seed) 14,475 1950 Bay Gardene (seed) 12,335 1951 Sister Lake 40,057 1951 Lake Felicity 10,000 1951 Bay Gardene (seed) 10,650 1952 Sister Lake 51,117 1952 Half Moon Island 35,841 1953 Sister Lake 30,474 1953 Half Moon Island 29,817 1954 Half Moon Island 36,205 1955 Mississippi Sound; Bay Boudreaux 34,883 Total 1,653,823 the summer of 1944, and that later, in 1949, 1950, and 1951, additional large plantings were made. At considerable expense, a watchman's camp was erected on the west shore of the Iake. But fungus disease and conchs proved too much, and the project was allowed to die. Walters (1952) stated, "Lake Felicity shell plantings to date have been unsuccessful." The use of Sister Lake ( Caillou Lake in Fig. 21) as a seed reservation began very early. Its history is probably better known than that of most areas, and it appears to have had a long, relatively useful life in seed oyster production (Table 6). Payne made the first plantings of shell in 1917. Sister Lake produced good oysters with intermittent TABLE 6 Sister Lake shell plantings, 1917 to 1953 Amount planted Year barreis May 1917 Summer 1941 Summer 1943 Summer 1944 Summer 1945 Summer 1946 1949 1950 1951 1952 1953 16,238 50,000 91,632 29,185 19,825 19,213 21,560 34,620 40,057 51,117 30,474 periods of poor condition up to 1941, when a regular system of shell plantings was developed, From 1943 each year saw from 19,000 to 90,000 barreis of shell bedded in Sister Lake. The amounts averaged 37,520 barreis per year from 1941 to 1953 inclusive. Shells are bedded at a rate of about 250 barreis per acre. This would mean that about 150 acres were shelled each year. Sister Lake contains about 7600 acres; thus each year about two percent of the area of the lake was covered. A gain in acreage covered would be made for about three years, so that an estimat.ed six percent of the entire area of the lake was maintained in a shelled condition at any one time. Payne (1920), in a map of the Louisiana coast, showed the entire hay as a prolifically producing area. lt is not believed that more than one-fourth has ever been productive. St. Amant et al. (1956) estimated that only about 600 acres is now productive, all in the north end of the lake. Such bays usually have large areas of mucky bottom in the center and only the margins and sorne central ridges are hard enough for good production. Perhaps about 75 percent of the productive area has been kept shelled for the past 15 years; if so, this is a very good record. Recently high-salinity water has encroached on Sister Lake. St. Amant (1955) showed that between 1951 and 1955 those months in which salinity was high enough to support drills increased in number from two per year to ten. He recorded increasing fungus disease as well as increasc in conchs, and stated that the Bay was 90 percent useless in 1955. Reclamation of this once great oyster-producing hay can be accomplished only by reduction of salinity either through cyclic weather change or through introduction of fresh water by engineering methods. lt would require an enormous volume of fresh water, estimated at about 1.6 billion cubic feet daily, to dilute nine square miles of high-salinity sea water. With the exception of severa! such areas as Sister Lake, it is believed that state shell planting in Louisiana is more of a public relations practice than anything else. The acreage shelled is not impressive when compared with the total area of natural reefs. McConnell ( 1932) stated that there were 50,000 acres of natural reefs in St. Bernard and Placquemines Parishes east of the Mississippi. From 1929 to 1953, a quarter century, an average of 57,248 barreis per year of shells was planted. At 250 barreis per acre this would plant 229 acres annually or less than 0.25 percent of the natural reef area east of the Mississippi alone, if it were all applied there. Physical and Chemical Conditions Louisiana's oyster-producing areas are shown on the map, Fig. S. Currently the best producing area is the "Louisiana Marsh" in St. Bernard Parish east of the Mississippi River. Sorne of the St. Bernard Parish production is in Mississippi Sound. The great productivity of this section depends on the Pearl River which keeps salinity low in the adjacent part of Mississippi Sound and the more northerly part of the St. Bernard marshes. In Placquemines Parish, east of the Mississippi, oysters are produced as far south as Grand Bay; most of this area from American Bay east to Black Bay and south to Quarantine Bay contains large seed reefs. Salinity in eastern Placquemines bays is controlled by the so-called Bohemia ( or Point a la Hache) Spillway, actually a gap in the levees on the east bank of the Mississippi beginning just south of Point a la Hache and extending about five miles down-river. Silting has much reduced the effectiveness of this spillway in recent years. Sorne oysters of low grade grow ali the way around the end of the Mississippi River. These are in the marginal bays which are sufficiently open to the Gulf to Jet oysters maintain themselves intermittently. In flood years ali of the oysters may be destroyed. These bays are now insignificant in overall production, but in the early years of the industry they were of considerable value. On the west flank of the Mississippi River, the productive area begins at Bay Tambour and Sandy Point Bay near the edge of the freshwater marsh. Fróm there oysters grow in all the bays and bayous to a point above Bay San Bois, westward to Little Lake (north­west of Barataria Bay proper) and to Bayou Lafourche. Most of this area has high salinity and high oyster mortality, as a rule. lt is the locale of the major part of the leases on which suits were based. West of Bayou Lafourche, important oyster production ex­tends to the Atchafalaya River, and includes Timbalier and Terrebonne Bays and ali tributary bays and bayous. Around Sister Lake (Caillou Lake) and Bay Junop is another intricate network of small bays and bayous, probably the most satisfactory of the producing areas of the state. Even this seems to be deteriorating because of the intrusion of high-salinity water. West of the Atchafalaya River there is sorne production, and oysters grow intermittently all the way to the Sabine River. In Atchafalaya Bay proper are the most extensive natural reefs in the state (Payne, 1912). These are mostly useless because they are solid high reefs, thickly studded with small misshapen oy~ters . which are so tightly packed and attached that they can be gathered only with a crowbar. Most of the Point au Fer reef near the mouth of the Atchafalaya is dead (from low salinity) and is being mined for shell. The westward end of the Point au Fer reef extends to Marsh Island where extensive reefs on the Gulf side are dredged for seed. An understanding of this complex of marshes, bayous, and bays depends on an under· standing of the nature of deltas of large rivers. The Mississippi River follows a channel between ridges of its own building, the natural levees, on which are built the artificial ones. The large bayous are deltaic distributaries of the Mississippi, or once were. These also follow ridges, their natural levees. Except for the Atchafalaya River and the "passes" in the lower subdelta, these distributaries have been severed from their con­ nections with the Mississippi by man-made levees, and no longer serve as distributaries. Between the major bayous are topographic basins, the deepest parts of which are the major bays. Flanking the major bays on either side are smaller satellite bays, and others of these extend inland. These inland bays may be far enough removed from the Gulf to contain fresh water only. An intricate system of tidal drains joins major and minor bays to each other. Many of these are sections of relict bayous which originally were parts of the Mississippi distributary system. The Barataria basin, lying between Bayou Lafourche and the Mississippi, is by far the most important basin in regard to the number and magnitude of claims of oyster mortality in 1940-1947. For this reason it was studied most closely by Research Foundation personnel and will be described in detail in this section. A less well-defined basin is that containing Timbalier and Terrebonne bays and their satellite bays and bayous. Originally (as late as 1860) this basin was at least three separate basins. The first extended from Bayou Lafourche westward to Terrebonne Bayou, which at that time occupied a raised ridge which carne to an end only a few miles from the Gulf near Caillou Island. The second included Terrebonne Bay and lay between Bayou Terrebonne and Bayou Petit Caillou. The third was west of Bayou Petit Caillou. At the present time, the lower ends of Bayou Petit Caillou and Bayou Terre­bonne are drowned in the expanding and deepening bays and the area is one large basin, indefinitely segmented in the northern portion. Bayou Lafourche has its origin at Donaldsonville, sorne 75 miles as the crow flies above its mouth just east of Timbalier Bay and west of the barrier islands which separate Barataria Bay from the Gulf. It is approximately 100 miles long. The Missis­sippi, forming the eastern boundary of the Barataria basin, is much longer, taking a circuitous route from Donaldsonville to the sea. Along the axis of the long triangular basin contained between these two major waterways are severa} large lakes, beginning at the northwest end with Lake Des Allemands, which is fresh water, and ending on the southeast with Barataria Bay. The map, Fig. 6, shows numerous distributaries radiating from Bayou Lafourche and the Mississippi which lead into small tributary bays which in turn connect with Barataria and Caminada Bays. Most of these minor dis­tributaries, severed from their parent distributaries by levees, and blocked in the fresh water zones with water hyacinth and alligator weed, no longer carry fresh water into the bays in significant amounts. The eastern margin of the Barataria basin continues down to the west side of the active delta of the Mississippi River. The river is no longer depositing sediment outside of its bed except in the area of fresh-water marsh forming the last 25 miles of the end of the delta. Across the southeast end of the Barataria basin there is a chain of barrier islands. The principal islands are Grand Isle and Grand Terre, which, with those Aanking to the east and west, form a large are separating the basin from the Gulf. The sea rim extending from Bayou Lafourche to the active Delta is broken by severa! passes, of which Barataria Pass is the largest. All of the oyster-producing areas of the Barataria basin are in the marshlands (including the bays). Variations in elevation are so slight that they are measured in inches rather than feet. Even the natural levees along the chenieres and major bayous are only inches higher than the marsh, and depths measurable in feet occur only in the bays and bayous. The coast of Louisiana, especially the active Delta, is sinking at a fast rate. Gunter ( 1952) has discussed references and rates of settling. According to his summary, the rate varíes from 0.05 to 0.163 foot per year. This includes both actual land subsidence and relative sinking dueto rise in sea leve!. Marmer (1954) records a rise in Gulf leve! at Pensacola of about 0.3 foot in the decade from 1940 to 1950, and at Galveston the rise was 0.5 foot. This indicates a rise of about 0.4 foot at Grand Isle, accounting for about one-third of the average change. Coupled with the sinking are other changes of a far-reaching nature. Disintegration of the shore-lines of bays and of the barrier islands is proceeding at a fast rate. Scour due_to increased fetch of the wind (Price, 1947) has prevented silt accumulations, so that the mean depth of bays is increasing. Levees of the Mississippi prevent large de­ posits of silt in the delta flanks which under natural conditions would be expected in flood times. The exotic plants, water hyacinth and alligator weed, are producing important changes in the ecological complex. The increase in the efficiency of the Mississippi River levees is one of the most important of the changes, because it has eliminated crevasses in flood period. The date of the last important crevasses which let river water into the Barataria region ( 1927) is an important turning point for the oyster industry. Rasmussen and Lynch (1949) have shown that sediments in Barataria Bay are becoming finer, and that there was a tendency toward poorer sorting of particle size in 1949 compared with data from 1934 (Krumbein and Aberdeen, 1937). lt is believed that more frequent encroachment of high-salinity water in recent years tends to pre­cipitate finer particle sizes by flocculation. Other changes possibly contributing to deposit of finer sediments are a decrease in frequency of scouring by floods from crevasses, a decrease in tidal current rates in certain parts of the hay due to closure of passes to the east of Grand Terre, and acceleration of the rate of disintegration of shorelines. The last change would produce a greater deposit of unsorted materials due to slumping. Barataria Bay depths seem not to be in equilibrium with the width and length of the Bay. There may be a lag in restoring equilibrium following abrupt changes caused by the improvement of levees and the severing of major distributaries. Nearly ali of the oyster production of the Barataria basin is in the "excessively drained salt marshes" of O'Neil (1949). However, as salinity has increased, the oyster industry has pushed into Little Lake northwest of Barataria Bay proper, and elsewhere into the "floating marsh" areas (Fig. 6). O'Neil's areas, which he believes are ecological entities, are shown on this map. Certainly the greatest part of the oyster industry of the Barataria basin is contained in the excessively drained marsh zone, ali of which is subj ect to tidal currents. Our own ecological studies were for the most part directed to:ward analysis of the salinity patterns, water movements, and other major environ­mental factors affecting oysters in that zone. TrnEs AND TrnAL CuRRENTS Reports by Marmer ( 1935, 1947, 1948) contain data on volumes of water movement through the principal passes into the Greater Barataria Bay area and Timbalier­Terrebonne Bays, as well as data on the tides and tidal currents. A tide station has been maintained since 1947 in Bayou Rigaud, an arm of Barataria Bay near Barataria Pass, in collaboration with the U. S. Coast and Geodetic Survey. During 1947 two subsidiary stations for collecting tide data were maintained at Manilla Village in Upper Barataria Bay and in the northern part of Bay Baptiste, a northeast extension of Barataria Bay. Marmer (1954) described the general features of tides in the northern Gulf area, and defined the types of tides, seasonal variations in tide level, and cyclic increase in Gulf level from 1909 to 1950. Tides are of the diurna! type, i.e., there is one high and one low per day. There are occasional days when two high water periods and two low water periods occur in one day. Times of high and low water fluctuate erratically from day to day, but tend to average out, over a long period, about 50 minutes later each succeeding day. At periods of equatorial tides the range may be only 0.1 foot or even zero on rare occasions. Such low ranges result from the effect of wind. The range at equatorial tide periods is usually 0.2 to 0.4 foot. At tropic tide periods normal ranges of 2.2 feet have been recorded, but 6 .5 6 .0 MEAN TIOE L EVEL FOR wº 5 .5 .... z o ...: t:l 5.0 .... 4 .5 4.0 2 3 4 5 6 7 B 9 10 11 12 13 14 15 OAYS, SEPTEMBER, 1951 FrG. 7. Typical tides at the Bayou Rigaud station from an equatorial tide period through a tropic tide period, and return, Sept. 1 to 15, '1951. the usual range is 1.4 to 1.8 feet. Fig. 7 shows tides for the period from September 1, 1951 to September 13, 1951; this graph may be taken as typical of a period of high mean tide level. In Fig. 8 is shown a graph of tides before, during, and after the passage of hurricane Flossie in September, 1956. The peak shown on September 24 is the highest level attained in the period from 1947 to 1957. Damage to roads and property by the BUILOUP TO MAXIMUM STORM IN THtS PERICO ~ DAMAGE TO H1GHWAY ANO BUILOINGS AT ( \ r GRANO ISLE WAS IN THIS PERIOO 9 .8 9.4 9 .0 8 6 8 .2 7 .8 7.4 ... w 7 .0 w .... 6 .6 6 .2 5 .8 5 .0 5.4 .. /'--.., MEAN TIDE LEVEL FOR ALL SEPTEMBERS FROM :~50 T07 .......,....L_ 27· 19 20 21 22 23 24 25 26 28 29 OAYS IN SEPTEMBER FrG. 8. Tides at Bayou Rigaud during passage of hurricane Flossie, data from Sept. 19 to Sept. 29, 1956. receding tide following the passage of the hurricane was very great; little damage occurred as the tide rose. Winds in this hurricane were not exceptionally high. The period of increasing wind velocity coincided with a normal flood tide, and it happened to be near the maximum of a tropic tide period in the month with the highest mean tide level of the year. This coincidence accounts for the great build-up of Gulf water in the bays and marshes behind the barrier islands, Grand Isle and Grand Terre. When the wind changed with passage of the hurricane, it coincided with the beginning of ebb tide. The consequent rush of waters back into the Gulf produced great damage to highways, boats, and buildings. Mean tide levels fluctuate in a regular rhythm throughout the year. The lower mean levels are in January, and the highest in September (Marmer, 1954). Fig. 9 shows the mean monthly tide levels for the six-year period from 1951 to 1956 as recorded by the Bayou Rigaud tide gauge. The increase in mean tide level from August to September is of the greatest sig­nificance in its effect on salinity levels in the bays and particularly in the marshes far above the bays. During approximately one month's time the bays may deepen by more than one-half foot. With low rainfall in the marsh drainage area, high evaporation rate due to midsummer temperatures, and high transpiration rate of lush summer marsh growth, the net flow of water from Louisiana bays during this month is not to the Gulf but into the marshes. Much of the marsh area is near sea level and large areas are covered with floating marsh. Transpiration can, under conditions of rainfall deficit, actually reduce marsh level at the same time that tide level takes a steep climb. The effect is a rapid transfer of salt water far inland. A more detailed discussion of this effect is contained in the section on salinity. Range of tide also varíes overa cycle of 18.6 years (Marmer, 1954). The maximum­range periods were in 1931-32 and in about 1950-51, while the minimum-range period between these two peaks lies at about 1941, with another to appear in 1960. 54 " ~ 5.1 ~5 o z o 46 4 7 4 6 4 5 MONTHS F1c. 9. Mean monthly tide leve! at Bayou Rigaud, 1950 to 1958. Perhaps the most important factor related to tides has been a steady rise in sea level over most of the century, affecting the entire Gulf. According to Marmer the amount of this rise at Pensacola was about 0.01 foot per year from 1924 to 1941. Thereafter the rate was sharply increased to 0.03 foot per ycar. At Galveston the increase in this latter period was at a rate of 0.05 foot per year. Study of tide records at the Bayou Rigaud station for the years 1951 to 1956 indicates that the rise is continuing, the rate ap­proximating that at Pensacola. Whether the rise in sea level is an actual rise, a relative rise due to sinking coast line, or both, is not clear. lt is believed to be a combined effect of both. The result has heen a general encroachment of saline waters inland, the effects of which are discussed elsewhere. Marmer's figures showing rise of Gulf level at Pensacola and at Galveston are reproduced in Fig. 10 . F1c. 10. Yearly sea level at two Gulf stations, after .\farrner, 1954. Marmer (1935) estimated the area of tidal waters of Timbalier and Terrebonne bays as 450 square miles in round numbers. From tidal ranges in the lower, middle, and upper parts of the hay, and the Greenwich time intervals, he calculated that an average of about 15 billion cubic feet of Gulf water flowed through the passes into these bays on each daily flood tide. At tropic tide periods the amount was more, and at equatorial tide periods it was less. Similarly, he calculated the movement into Greater Barataria Bay through the several passes (Caminada, Barataria, Quatre Bayou, and Abel). The data are reproduced here as Table 7 which is taken from Marmer (1948). TABLE 7 Tidal llow of water through passes of the Greater Barataria Bay Area. Figures are millions of cuhic feet. Data from .\farmer (1948) Pass Flood flow Ebb flow Ebb excess Caminada Barataria A bel Quatre Bayou 627 3229 129 874 653 3438 212 1005 29 209 83 131 Data on currents from which Marmer calculated the volumes in Table 7 were obtained during August, 1947. Those for Barataria Pass are most reliable, observations having been carried through an entire tidal cycle. Austin ( 1955) used Marmer's data to cal­cula te a flushing time of 23 days for all of Barataria Bay. The total mean volume of water in Barataria Bay was calculated by Marmer to he about 15,391 X 106 cubic feet. Currents in Barataria Pass had a mean flood strength of 0.79 to 1.55 knots and mean ebb strengths varied from 0.87 to 1.59 knots. In upper Barataria Bay, in open water, mean velocity was 0.21 knots at flood and 0.31 knots at ebb tide. These latter figures are representative of open hay current conditions where cross-sectional areas are very large. ÜXYGEN, REDox PoTENTIAL, AND HYDROGEN SuLFIDE JN THE BARATARJA AREA Oxygen in Barataria Bay was studied by Hewatt (1949, 1953, 1955) and Jensen ( 1949) . Most of the oxygen determinations were made in 1948 by J ensen and associates. Oxygen measurements were made on more than 1100 samples taken from all parts of the Greater Barataria area in all months of the year. Water samples were taken from a level about one foot over the bottom, and simultaneous measurements of redox potential (Eh) were made. The relation of the readings to tidal cycle was determined. The relations of oxygen tension and redox potential were also studied by taking continuous Eh readings accompanied by oxygen titrations over short periods at set stations. Hewatt made supplementary studies on conditions in small marsh ponds distributed from brackish to high-salinity areas. Many water samples were tested for hydrogen sulphide. The number of positive readings was very low; in fact, in the open parts of Barataria Bay they were almost non-existent. Positive tests could be found occasionally in sorne small bayous and shallow marsh ponds where concentrations of organic substances were high. Bleedwaters were also checked for hydrogen sulphide and an attempt was made to measure the influence of these in contributing hydrogen sulphide to the waters. This influence was found to be too small to measure. Oxygen determinations by Jensen were made by a modified Winkler method. A Beckman Model G meter was used for measurements of oxidation-reduction potential; the results were expressed in millivolts. Platinum and calomel electrodes were used, and · readings were made in the field. Except where noted ali determinations were ata level of about one foot over the bottom. Fig. 11 is a summary of 1134 values for oxygen taken in ali months of 1948 and 4ij 1 / 01 USTR•f:l..ITIC~ _ ;lh'[ f011 OISSO....,EL C~ •G<"'< " U°"BER OF RfAO 2'.500 .._, ;:: z ~400 o Q_ X §300 a: > ~400 _,.. ;:: z ::'30 á' X S200 a: .._, ;:: ~20 á' ~· 100 o il! 1600 1800 2000 2200 2400 0200 0400 0600 0800 1000 1200 OEeEMSER 18, 1947 DEeEMSER 19, 1947 Eh'--------/// , CONTINUOUS RUN neo. eAMP _,., LAFITTE 100 YO. WEST OF L.LE. 1/ o.o. -______...------.-----~-" .._____:r-­ 2200 2400 0200 0400 0600 0800 1000 1200 OEeEMBER 19, 1947 OEeEM8ER 20, 1947 CONTINUOUS RUNEh T.T.CO. CllJIP LAFITTE _...... -­ ~¿'; 2000 2200 2400 0200 , 0400 0600 0800 /000 1200 J.l.NUARY 23, 194a JANl/ARY 30, 1948 CONTINUOUS RUN Eh ,,...------... _ neo. CAMP LAFITTE -............... --....._ ' ' / -­ ..--......... /// ................. , __ .¡ o.o. 1600 1800 2000 2200 2400 0200 0400 0600 0•100 IOOO 1200 1400 JANUARY 31, 1948 FEBllJARY 1, 1948 CONTINUOUS 11\JN STATION 51 T.T.CO. TANK 8ATTERY 1800 2000 2200 2400 0200 0400 APRIL 21, 1948 APRIL 22, 1948 CONTINUOUS RUN STATION 1 1() ~ ¡:¡ o 8 ~ i5 "' 8 i Q_ !!: 6 z w >­ "' X o 4 o ~ o ::¡ i5 ¡ J!¡ z w 12 C> >­ X o o :;i '.'; g ¡g i 12 ~ ~ C> >­ X o o o w '.'; 8 :il "'i5 i Q_ !!: /O ~ C> >­ X 8 o o ~ 6 g i5 "' :E 8 "' !!: ~ "' ~ o :;i 4 '.'; ~ 6 1200 1400 1600 1800 2000 2200 2400 0200 0400 0600 0800 /000 APRIL 25, 1948 APRIL 26, 1948 FrG. 13. Comparison of redox potential and oxygen values at six stations in the Barataria Bay area. Samples were taken simultaneously. muds near shore is greater than in muds at considerable distance from shore. Slumping, as the shorelines disintegrate, causes decaying marsh turf rich in plant debris to accumulate along shores. Examination of the locations of Valentine and McCleskey's redox potential values in the low positive class shows that they are all in the smaller detritus:laden bays ornear disintegrating shorelines. Hewatt ( l 953b) has shown that the oxygen content of water in small marsh ponds may change very rapidly. One pond studied by him recovered from a low of five percent saturation to a high of 112 percent in the period oflO hoÚrs. The minimum value was recorded at 0415, the maximum at 1430, showing the effect of photosynthesis. Part of the gain appeared to be the result of an inflowing tide. This pond was only six inches to one foot deep, depending partly on the tide stage. Such ponds lack the conservatism of the large bays, in capacity to limit oxygen fluctuation. The pH changes in this pond were rather small during the extreme oxygen fluctuations recorded above, indicating that redox potential may not have changed greatly, pH being to sorne extent a function of the Eh (ZoBell, 1946). TURBIDITY Bays and bayous of the Mississippi River delta depressions are generally turbid. Much of this turbidity is due to materials carried to the Gulf by the river in the past; because of the levees the present suspended silt load of the river is a relatively minor factor; the saline Gulf water, into which the river now passes, precipitates most of its silt load. However, there are no oyster-producing areas in Louisiana where the water is clear in the sense that offshore waters are clear. The normal turbidities occurring in Barataria and adjacent bays are always high, probably higher than in most other oyster-producing regions of the United States. When the investigation began, there seemed to be a chance that excessive turbidity might in sorne manner affect mortality rates of oysters in Louisi­ana. Data on normal turbidities in Barataria Bay, collected by W. G. Hewatt, have been presented in serveral reports (Hewatt, 1949, 1953a, 1955). Most of Hewatt's turbidity measurements were made by means of photoelectric cells set at a point on a glass tube through which sea water was pumped in a constant stream. Hewatt estimates that about 100,000 hours of turbidity readings were recorded on Esterline Angus recorders. Cali­bration was made by means of standard fuller's earth suspensions, and checked against a Jackson candle turbidimeter. The stations for taking turbidity measurements were the same as those for salinities (see Hewatt, 1951, for a complete series). A combination of high wind and rainfall operated to produce the highest turbidities recorded. Sorne of these were in the range of 400 to 900 ppm. Such high turbidities were of short duration, normally lasting a matter of hours. But turbidities of severa! days duration were encountered in the range of 200 to 400 ppm. Under conditions of calm, and Iittle fresh-water inflow, turbidity dropped as low as 10 to 20 ppm in high salinity regions. Probably as many as half of all records showed turbidities in the range of 20 to 50 pprri and about 25 percent more in the range from 50 to 100 ppm. Turbidity readings·at a station did not always reflect turbidities over all of a hay, and demarkation lines between areas of high and low turbidity were often abrupt. On one occasion, turbidities ranging from 18 to 198 ppm were recorded with an electro­photometer while drifting a distance of less than 200 feet. In this case the boat was drifted by the wind across a tidal tongue of high-salinity water which entered a small hay at a comparatively narrow pass. Such tongues of high-salinity water appear and are completely erased with great rapidity. Even when a bay appears equally turhid everywhere, considerable local differences in turbidity measurements may occur; these are probably associated with small depth differences. In one test, three stations about one-half mile apart and forming a rough equilateral triangle showed turbidities (mean of three readings at each station) of 77 ppm, 32 ppm, and 63 ppm. Such differences are found in open water on a windy day; near exposed shores they may occur at nearly any time there is wind. Rolling of waves against a muddy shore often produces very local turbidities of 300 to 500 ppm. Those shorelines most exposed to wind action are favorite places for oyster leases because loose silt is kept scoured away. After attaining a peak of high turbidity, the water usually clears quickly. For ex­ample, Hewatt's data show that at Station 51 in Barataria Bay on June 9, 1948, the turbidity reached 600 ppm at 1900 and three hours later had dropped to 200 ppm. The highest natural turbidity recorded by Hewatt was about 890 ppm at Station 51 on De­cember 30, 1948, at about 1830. This dropped to 200 ppm in 21/2 hours. Further clearing helow 200 ppm is apt to be much slower for ohvious reasons. Under conditions of con­tinuous wind and heavy rainfall, turhidities may he maintained at a leve! of as much as 200 ppm over a period as long as 36 hours, and there is one record (at Station 51 on Novemher 29, 1948) of turhidity remaining in excess of 300 ppm for a 24-hour period. This station showed turhidity levels fluctuating hetween 100 and 800 ppm from ahout noon of Novemher 28 to midnight of November 30; during this period there were nine maxima in the range of 500 to 800 ppm and 10 corresponding minima hetween 100 and 400 ppm. High turhidities in the ranges indicated were never sustained longer than 2% days. On the other hand, turhidities of around 100 ppm were often sustained for a week or more. In the period from January to April turhidities are much higher than in other months of the year. From June to Octoher turhidities are generally low. Other things heing equal, high salinity areas have lower turhidities than do the low salinity regions, hecause of the precipitation effect of saline waters. Almost from the heginning it was ohserved that mortality of oysters was in inverse proportion to the turhidity of the water. Stations with low salinity and high turhidity, such as Chene Fleur, had markedly lower mortality rates than did stations such as Sugar House in the southern part of Barataria. Mortality rates at this latter station were as high as any encountered anywhere. There the hottom was a hard mud-sand mixture with no loose silt, and it was frequently ohserved that the water would he comparatively clear there when it was turhid at other stations. Most commercial oyster leases are located along the margins of the hay, close to shores where wave action stirs up silt, and therefore have higher turhidities over them than can he found in open waters far from shore. Seasonal mortality rates were much higher in summer months when turhidity was generally low, and those months with frequent periods of high turhidity, January to April, had the lowest mortality rates of ali. Because of these ohservations there was an early loss of interest in turhidity as a possihle factor in mortality of oysters. However, sorne experimental work has been done on the effects of turhidity. Methods were developed for maintaining constant high turbidity levels in aquaria, and a series of experiments was conducted to test the effect of silt suspensions on survival of oysters (Mackin, 1956b). The data from these studies are presented in Table 8. Maximum turbidity used in experiments was 700 ppm. As shown in Table 8 this concentration pro­duced no significant mortality in the experimental oysters_ For details of the apparatus used see Mackin ( 1956b) . TABLE 8 Mortalities of oysters in experimental and control aquaria of the turbidity experiments. There were 20 oysters in all control and experimental tanks. x =experimental tank; c =control tank. ' All studies !asted 21 days Maximum and minimum Approximate Number Percenl Experiment lurbídity readings average lurbidity oyslers eysters number ppm ppm dying dyiog Dates 1-x 99-110 100 o o.o 2-28--55 to 3--21__:55 1-c 0-27 15 1 5.0 same 2-x 185-216 200 3 15.0 4-5-55 to 4-26-55 3-x 290-318 300 2 10.0 same 2-3-c 4--:30 15 4 20.0 same 4·X 390--420 400 7 35.0 4-27-55 to ~18-55 5-x 490-532 500 4 20.0 same 4-5-c 0--27 10 5 25.0 same 6-x 49~720 590 3 '15.0 5-23-55 to 6-12-55 7-x 639-765 710 4 20.0 same 6-7­c 0--45 15 3 15.0 same WATER TEMPERATURE Water tempera tu re proved to be of primary importance. Mortalities of oysters were obviously correlated with temperature, since they were seasonal. The pattern of tem­perature change varies little from year to year. The graph, Fig. 14, shows temperature changes from July, 1948, to August, 1949. Lowest water temperature on record was 2°C in Bayou Rigaud on February 3, 1951. On that date air temperature dropped to -5°C, water in the margin of Bayou Rigaud had a thin film of ice, and many fish (mostly Cynoscion nebul.osus) died as a direct or indirect result of the sudden cold. The highest water temperature recorded in open water was 35°C on the third of July, 1948, in Barataria Bay. Small bayous which drain from exposed mud flats may reach tempera­tures up to 40ºC in summer. Most summer water temperatures range between 27° and 32ºC. Occasional very warm periods in winter have been observed. In January and February of 1957 there was a period in which water temperature was above 20ºC for sixteen consecutive days (Mackin and Sparks, 1958). SALINITY Salinity in estuaries of the Mississippi Delta is probably the most variable component of the environment, and is dependent on a greater variety of modifying conditions than any other with which Project 9 had to deal. Much time and effort went into measure­ment of salinities. Early references in the literature (Hewatt, 1951) consisted of "spot" records which 36 34 DAILY RANGE OF WATER TEMPERATURE 32 30 28 26 24 22 );-' ~20 a:: ¡:: 18 ­!:::: z _J <[ 40 •o SATUROAY ISLAND STATION 60 21 • 11 11 2& o 40 •• 20 ;,!!o z >­1­z ::::¡ <[ 40 MIO-BARATARIA BAY AT BAR. LIGHT 40 STATION 50 30 "' o.. 7 14 21 21 5 12 ,. 26 2 1& 23 JO ,. 20 27 4 11 11 21 JUNE JULY AUGUST SEPTEMBER OCTOBER F1G. 17. Salinity changes in summer and fall at five stations in Barataria Bay, La., 1947. Rainfall scale is included. The effect of continued sub-normal rainfall over severa! months is shown. hay (generally low salinity) through graded steps to the south, ending with Station 18 which is situated just inside the hay at Barataria Pass. The salinities show a gradual increase during the "drouth" period. Note that it is not a drouth in the usual sense, for rain was recorded -0n 21 days in August. At Station 10, where salinity is nonnally quite low, it ranged between zero and 10 ppt in June, increased to the end of October, and ended with the last 10 days fluctuating between 21 ppt and 25 ppt. At the other extreme, Station 18, just inside Barataria Pass, started in June with salinity fluctuating between 11 ppt and 22 ppt, and ended in October with a range between 27 ppt and 34 ppt. Stations 50 and 18 are in "normal" conch territory; the three northerly stations do not ordinarily have salinity high enough to permit these predators to live. Ali of the stations from late July to the end of October attained salinities well within the tolerance of Thais haemastoma. Those stations which have one or more annual low salinity periods, long enough to kili conchs, are the ones free from conchs under normal conditions. The mean salinity at such stations may be well above the tolerance limit; it is the extremes, not the means, that limit the dep· redations of Thais. The increasing salinity in the case discussed here probably was enhanced considerably by the increasing leve! of the ti de. Water levels in the marshes above Barataria Bay must increase equally with Gulf levels to offset the effect of higher mean tide. The latter would act as a sort of a dam, which is shifted farther inland in the case of rainfall deficit of long duration. Thus the rising salinity was produced not only by deficit of rainfall; there was also a decrease in the proportion of fresh water to sea water in the hay because of an increase in volume of sea water. In the winter months this effect is reversed. From September or October, when highest mean tide leve! is reached, there is a rapid lowering of mean tide leve! until January. In this period of three months, mean tide leve] drops about 0.9 foot (nearly 11 inches). This lowering of the "salt-water dam" incn~ases the effect of rainfall in lowering the salinity. For example, the period of rainfall deficit shown in Fig. 17 was followed by excess rainfall of nearly 12 inches during November and early December, 1947. This was sufficient to keep salinity levels low in the upper hay during the following two-month period of deficit rainfall, until February, 1948. Stations in the lower hay were definitely depressed, but recovered in a period of less th:m one month. EFFECT OF THE MISSISSIPPI füVER The Mississippi River once exercised control over salinity in ali waters of the Delta marshland. With the construction of levees this major influence was steadily reduced (Gunter, 1952) . Even after levees were complete and about as they are today, frequent crevasses produced highly effective flushing of major portions of the Delta. The last of these, so far as the west Delta flank is concemed, occurred in 1927. Since that time the Mississippi River has had sorne effect in lowering salinities in Barataria Bay but only when the river is in flood stage. Fresh water discharged into the Gulf through Southwest Pass and other mouths of the river is stratified over the highly saline Gulf water, and is carried into Barataria and other passes by tidal movement. This may be very effective in lowering hay salinities during periods of high river discharge, especially from Sandy Point to Bastian Bay on the lower west Delta flank. A lesser effect is sometimes felt in Barataria Bay. The surface currents from thc end of the Delta pass westward along the coast and are progressively closer inshore from winter to summer. The fresh water layer may get deep enough to block the deeper saline water from the passes. The effect is transient. The effect of encroachment of low-saliniiy water from the Gulf into Bastian Bay is shown by records taken by Hewatt (1951) on March 23, 1948, and April 24, 1948. The river was in high stage in March and April of that year ( 128.4 and 120.3 percent of the means respectively for those months). For comparison, data from December 23, 1947, are given. The data are presented in Table 9. TABLE 9 Effect of Mississippi River leve! on salinity in Bastian Bay. Salinity measured by titrating spot samples of water Salinity Salinily Salinity Dec. 23, 1947; Mar. 23, 1948; April 24, 1948 ; Stalion river level 78o/o o{ mean; ppl river level 128% of mean; ppl river level 120% of mean; ppl Bayou Cook above Bastian Bay 18.4 13.2 12.9 U pper Bastian Bay '23.5 1'2.7 13.0 Lower Bastian Bay 26.0 9.8 11.8 Pass to Gulf 31.3 6.5 11.5 The greater effect on March 23 may be due to lower Gulf level at that date, and possibly difference in tide stage. With the river leve! at only 78 percent of the mean on December 23, 1947, it is obvious that the fresh water dilution of Bastian Bay carne from land drainage, which is small at this point on the Delta flank. The small bays of the lower west Delta flank are dependent on Mississippi flood conditions for most of their fresh water. 1t is for this reason that oyster mortalities associated with high salinity have been frequent throughout the recorded history of the area. Two figures from Hewatt ( 1951) are reproduced to present ranges and modes of salinity (Figs. 18 and 19), at two stations. Station 17 is in a small hay ( Chene Fleur) above Barataria Bay proper and is in the low-salinity zone of oyster production. Station 51 is in the middle of lower Barataria Bay. The difference between the ranges at the two stations is less than the daily tidal variation at one station in the high-salinity area. The modes, however, are significantly different. The low'salinity station at Chene Fleur tends to have two modes, one produced by low salinities in March, April, and May, and another by relatively high salinities in July, August, and September. Other months tend to have salinities spread more or less equally from low to high. lt is of interest that the high-salinity months are the months of mean high precipitation. Rising mean tide levels, transpiration from vegetation, and evaporation more than offset the higher rainfall. High precipitation during the summer is succeeded by severa! months of mean low rainfall. During ihe fall months, salinity levels usually show a gradual increase and high-salinity waters move into the upper reaches of the bays and bayous above Barataria Bay proper. SALINITY GRADIENTS FROM EAST TO WEST IN BARATARIA BAY So far the discussion has involved only salinity gradients from the passes on the south to the north. There is, however, a very definite east-west gradient also. Most fresh water drains into Barataria Bay from the northwest, through Bayou St. Denis, Grand Bayou, Bayou Cholas, and Wilkinson Canal. Wilkinson Bayou and other northeast entry ways are less important. There is a relatively small watershed to the east, bounded by the Mississippi River levee. The freshwater inflow tends to move down the west side of the o a: o >-N ~"' Q. o ~o Q o ..J >-º ÍÍ:N Q. o "'"' "'ºQ ~ ,..o o >0 "'º º"' z "'"' o o Q Q o "'º o "'"' o Q o zO ~"' o Q o o ., o :>N "'º "'... "' "' o o Q Q F1c. 18. Salinity frequencies at station 17, Chene Fleur Bay, September, 1957, to August, 1958, after Hewatt, 1951. hay, aided by Coriolis force and prevailing easterly winds. These conditions often produce isohalines which traverse the hay from south to north. Pockets of high salinity waters in the east and northeast paits of the hay are of common occurrence (Fig. 20). Tributary bays, such as Lake Grande Ecaille, lying to the east of Barataria Bay proper, often show comparatively lit'tt effect of freshets. More nearly stable high salinity is therefore characteristic of the easterly areas. RisrnG SALINITY DumNG THE FrnsT HALF oF THE 20TH CENTURY Many references in the literature indicate that the salinity leve! in the oyster­producing bays of Louisiana has been increasing since the beginning of the century. In fact, the beginning of this phenomenon probably far antedates 1900. Early salinity records only doubtfully support this thesis. A careful study of the early records (Hewatt, 1951) lea ves the impression that it could be true. Bur the spotty nature J: RAINFALL: 17.9 IN. Uo a: o -o _J o ;; ­ o "' 5 "'º ::> o ºº z- o "' uo wo o- o "' RAINFALL: 6. 71 IN. RAINFALL: 12.89 IN. RAINFALL: 1.13 IN. RAINFALL: 10.25 IN. RAINFALL: 4.83 IN. FrG. '19. Salinity frequencies at station 51, Barataria Bay, Louisiana, from March to December 1948, after Hewatt, 1951. of these records makes a valid comparison impossible. They prove only that in par­ticular areas there were periods of both high and low salinities, with no indication that one or the other predominated. However, the references in the literature indicate that, at about the beginning of the century, generally lower salinities prevailed. To review sorne of these briefly, Cary ( 1906) stated that freshets were "by far the most formidable destructive agent to be encountered" by oyster culturists. Agairí ( 1907 a, l 907h) he repeated his earlier state­ment, but said that this danger was less in Terrebonne Parish than was the case farther west. Gates ( 1910) warned against selection of leases for oyster culture in low-salinity areas. Moore (1899) stated that the probable reason why oysters had never been produced in the northern part of Barataria was because of the "low normal salinity," 4.6 Studies on Oyster Mortaüty F1c. 20. lsohalines in Barataria Bay, March 10, 1949. The gradation of salinities from west to east is caused by large volumes of fresh water from excessive rainfall which fell in the Barataria watershed from March 3 to March 10, 1949. After Hewatt, 1951. and reported that a dead reef in Little Lake (of Lafourche Parish) may have been destroyed by fresh water. He stated that Terrehonne Bay was too fresh for the conch (Thais haemastoma) to live. Other records indicate that this was not true of ali oí the hay, but it may ha ve been true for the more northerly half. Baylor ( 1904) advocated construction of locks and dams for protection against freshets and crevasses, which he thought constituted the greatest danger to Louisiana oysters. The locks and dams re­ferred to were on the Arkansas and Missouri Rivers. In 1908 the Oyster Commission of Louisiana recommended that the Baptiste Collete Gap on the lower east bank of the Mississippi River be closed to cut off fresh water from certain areas east of the river. The opinions in this matter were not unanimous, even at the turn of the century. Apparently low salinity effects were observable in certain localities while in others the troubles were either indeterminate or associated with predation in high salinities. As the years passed, low salinity, except as associated with crevasses or spillway openings, ceased to be mentioned and the association of mortalities with encroachment of high salinity became more and more frequent. A detailed discussion of the references is given in the section dealing with the oyster industry and will not be repeated here. By about 1940 to 1950 the concept of increasing salinity was firmly established in the literature. Characteristic of the reports of increasing salinity was the absence of actual salinity data supporting the thesis. lt was not clear whether or not the "increasing" salinity meant actual progression to a higher level, the maxima of which exceeded past maxima, or whether the number of recurrences of high salinity periods was increased. Perhaps it may have been an increase in duration of high salinity periods rather than increase in number of such periods. An exception to the rule that reports of increasing salinity were not documented has recently appeared. St. Amant ( 1955) presented salinity data for Sister Lake covering the period froml950 to 1955 which show a rapid increase. It paralleled collapse of the area as an oyster production center. From the beginning of the century Sister Lake had been an important seed producing area. In spite of the fact that most statements are not supported by actual data, it is believed that there has been a progressive change toward high salinities. It is the intention here to summarize the factors which are thought to have produced progressive change in salinities in Louisiana bays, with special reference to Barataria and its satellite bays and bayous. Sorne of the effects are well established while others are largely inferential. ( 1) Levees. Probably the most important of the factors having to do with salinity rise was the construction of the extensive levee system of the Mississippi. Gunter ( 1952) has reviewed the history of the levees. lmportant milestones should be pointed out. By 1904 the system of levees cutting off river water from the delta basins between the Mississippi River and the Atchafalaya basin was complete and Bayou Lafourche was cut off from the river in that year. lt was the last of the major distributaries to be so severed. But frequent crevasses continued to bring intermittent relief until 1927 when the levees were shattered by a vast flood. After that the U. S. Army Engineers assumed re­sponsibility for maintenance and built the levees higher. They completed the system in 1935, when it included 2130 miles of confining embankments. The date of 1927 marked the end of the crevasses which let river water into the high-mortality region west of the river. Elimination of crevasses meant the loss of one of the most effective agencies controlling enemies and competitors of oysters. ( 2) Rise in Gulf leve!. Marmer ( 1954) has shown that there has been a steady rise in Gulf leve! beginning early in the century. Rise in Gulf leve! means a lessened gradient from the watershed into the bays with consequent retention in the fresh-water marshes of a greater quantity of fresh water. At the same time subsidence has deepened the bays (see summary of references by Gunter, 1952). The increased depth and higher water leve! have increased the volume of water in the bays, requiring a larger fresh-water volume for dilution to any given salinity. Since it is apparent that the required fresh­water increase has not been provided, an increase in salinity necessarily took place. (3) Blockage of drainage distributaries in the fresh-water marsh. Water hyacinths probably were introduced into Louisiana in 1884 (Wunderlich, 1941), and alligator weed appeared at about the same time. By 1900 these exotic plants had spread and increased until they were a serious menace to navigation. Much study and effort was put into attempts to control these pests, with considerable success in the larger, more im­portant bayous. But in the minor distributaries, and in ponds and lakes of the fresh­water marsh, little has ever been done. Most of these minor distributaries and much of the pond area in the marshes hecame completely filled with the plants, and alligator weed invaded the land areas of the marsh. These two exotic plants contributed to the deficit of fresh water in the oyster­producing area in two ways. First, they prevented movement of water by mechanical blockage, and second, they retumed large amounts of moisture to the .air by transpira­tion. There is now a well-defined zone in the fresh-water marshes that is without drainage except for the major waterways, natural bayous and dredged canals, which are kept clear for navigation purposes. Vast arcas of the fresh-water marshes are undrained because the bayous follow natural levees which are higher than the intervening marsh basins. Water tends to drain away from the bayous rather than in to them. On the other hand, artificial canals cut through all levels, and drain marshes better than the natural bayous. There is no known way to measure the total effect of hyacinth and alligator weed, but they must have large effects. (4) Disintegration of shorelines and islands. For many years the bays of the west Delta flank depression have been widening and deepening. Shorelines disintegrate at a fast rate, and whole islands have been observed to disappear within the last 10 years. lncreased wind fetch and consequent increased scour has helped deepen the hays (Price, 1947). Sediments of the Mississippi River formerly deposited in the Delta are now deposited in the Gulf proper. Subsidence has contributed to the depth of the hays. These increased basins now contain much more water than was the case at the beginning of the century. The additional water comes from the Gulf, while the fresh water supply has decreased. Doubtfully, there may be a decreased f!ow of the Mississippi River and a tendency to change the pattem of ftow. This cannot be determined with certainty. If it is true, the small bays of the lower west Delta ftank may get less fresh water, at critica! periods, from this source. There are certain factors that have not contributed to increased salinities. Rainfall has not decreased perceptibly in thc last thirty years. According to the data assemhled by Hewatt ( 1955), rainfall in the Barataria. watershed was somewhat greater in the period of 1940 to 1949 than it was in the decade from 1920 to 1929. Neither has there been any detectable change in the pattern of rainfall. Canal dredging, sometimes assigned a role in increasing salinities (McConnell, 1956), can hardly be a contributor. Additional canals do not admit more water from the Gulf, since the depth to which the bays fill on flood tide is controlled by Gulf leve!, not by the number of access waterways. The saline marshes are already well drained, not being affected by blockage as are the fresh-water marshes. Canals dredged in the fresh­water marsh and connecting with the saline bays might conceivably be of benefit in reducing salinities in the highly saline areas. lf the fresh-water areas were completely leveed from saline waters, canals connecting the two areas would admit saline waters to the fresh-water areas and vice-versa. In such a hypothetical situation, the net effects of the canals would damage the fresh-water areas especially in rice-producing localities, but they would benefit the oyster-producing region by lowering the salinity, and possibly by bringing in more nutrient substances. BIOLOGICAL SIGNIFICANCE OF SALINITY A drop of salinity below about 5 ppt, if long continued, will result in mortality of oysters. The time required to kill oysters varies according to the temperature and season, the previous condition of the oysters, their age, and perhaps other factors. Because of their ability to keep their shells closed for long periods, oysters can survive short periods of low salinity, even fresh water, that will kili most of the other organisms that live on oyster beds. Near the inland limit of the oyster's range, the fauna of oyster beds is normally composed of relatively few species. Sorne of these species, that share with the oyster the ability to tolerate low salinity, become far more abundant in this marginal zone than in higher salinity, presumably because of the relative scarcity of their enemies. These are called "low-salinity species." Sorne of them, e.g. Rangia cuneata, Congeria leucopheata, and Rhithropanopeus harrisii, can tolerate much lower salinity than the oyster and reach their maximum abundance even farther inland, beyond the range of the oyster. Others, such as Cliona truitti, do not extend quite as far inland as the oyster because they are less tolerant of extremely low salinities. lncreased salinity, unlike fresh water, does not have an adverse effect on the oyster directly. A continued high salinity, in southern waters, is unfavorable to oysters because it is favorable to their enemies: shell-boring organisms like boring sponges (Cliona spp., especially C. celata), the boring clam Martesia smithii, and the mudworm Polydora websteri; competitors for food and space like sea squirts (tunicates) and slipper limpets (Crepidula spp.); predators of spat and older oysters like Thais haemastoma and Menippe mercenaria; and disease-producing parasites such as Dermocystidium marinum. An increase in salinity large enough and long enough to !et these enemies become established will result in an increased rate of mortality among the oysters below the low tide level. In southern waters of continuously high salinity, oysters are confined almost entirely to the intertidal zone. Areas with normally high salinity become much more favorable to the development and maintenance of large populations of oysters after a freshet wipes out most of the high-salinity fauna. The following lists name sorne of the commoner species found on Louisiana oyster beds. "High-salinity" species are those that become more abundant as salinity increases, up to 35 ppt. As you go up the hay, or as salinity decreases, these species drop out one by one until only those most tolerant of low salinity remain. These remaining species are those named in the second list, "species more or less independent of salinity." Species that not only tolerate low salinity, but become more abundant as salinity nears the lowest level that oysters can stand, are na:med in the third list, "low-salinity species." Salinity Relations of Sorne Common Animals on Louisiana Oyster Beds l. High-salinity species: Cliona celata Grant, sulphur sponge, boring sponge Haliclona sp., encrusting sponge Astrangia astreiformis Milne Edwards an.-8 0.012 0.007 Ba 8-9 2 36-40 middle 12-18 0.013 0.006 Ba 12-14 3 32-36 top 4--12 0.074 0.008 Ba 17-19 3 37-40 top 4--6 0.018 0.003 Bq 1-6 6 32-40 middle 2-3 0.069 0.019 Bq 9-10 2 30-36 bottom 10 and middle ll 0.093 0.016 Bq 13-17 5 30-36 middle 2-6 and top 4 0.035 0.012 Bq 20-21 2 25-36 top 12 to top 20 0.053 0.019 Bq 24--27 4 20--25 top 2-8 0.005 0.014 Bu l-"17 17 20--40 top 10--22 0.046 0.002 Cn 1-6 6 0.065 0.0ll Bq 28-29 4 20--30 top 4-8 0.055 0.014 Totals 64 Average 0.049 O.Oll Study of these data shows that the "hydrocarbons" are associated with the plant remains, and it is believed that they are derived from the plants. The silty layers con­taining relatively small amounts of plant debris averaged 0.011 percent "unsaponifiable hydrocarbons" and the peaty layers averagecl approximately four times as much (0.049 percent). In ali sets of cores the peaty layers were significantly higher in "unsaponi­fiable hydrocarbons" than were the silty layers. Two samples of dried water hyacinths from Allen Lake, Bryan, Texas, were analyzed for "unsaponifiable hydrocarbons" to determine the content of these substances in remains of plants which were recently alive. These plants had been dragged from the lake and piled on shore in an effort to rid the small lake of the pests. The two samples of water plants had respectively 0.096 percent and 0.214 percent "unsaponifiable hydro­carbons," considerably more than most muo samples on the average, and much more than any mud samples taken from the vicinity of oyster beds in open waters of bays. Severa! core samples were taken in the Bay Ste. Elaine area in the vicinity of Texas Company wells drilled in exploration for sulphur. These cores were taken in the marsh­land, and the top four inches contained much living plant material in the form of roots. GULF OF MEXICO F1c. 23. Locations of cores tabulated in Table 12. These cores were used to compare "hydro­carbons" in peat with those in silts of the same cores. Most of these cores were taken in the east part of Lake Grande Ecaille. When analyzed those parts of the cores contammg the living plant material showed generally higher "unsaponifiable hydrocarbon" content than did the lower layers con­taining partially decomposed plant materials. The data are presented in Table 13­ TABLE 13 Cores taken in the marsh in the Bay Ste. Elaine area, January 20-21, 1948 Percent unsaponifiable residue al depth Series Top Middle Bouom TM ºl UM13 UM2 TM24 Mean 0.157 0.081 0.058 0.031 0.082 0.020 0.019 0.014 0.005 0.014 0.041 0.007 0.016 0.005 0.017 lt is concluded from these studies that living plants contain relatively more "hydro­carbon" than do plant remains which have been partially oxidized. The data presented here should be compared with the data in Table 25 showing "hydrocarbons" at different depths in cores from oyster-producing areas of Barataria Bay and adjacent waters. Most of the latter cores were taken around the margins of the hay ( where the oyster leases are generally located) , and in open waters for the most part. The Barataria Bay values are obviously lower than those associated with heavy deposits of plant debris and living plant tissue, as in the Bay Ste. Elaine marsh cores. Table 24 shows that values of samples from Bay Ste. Elaine field also are generally lower than in these marsh cores. HYDROCARBONS IN Muos AND TttEIR RELATION TO ÜYSTER MoRTALITY 1t was reasoned that, if the hydrocarbons in muds were related to oy'ster mortality, there should be a significant correlation of high mortality and high "hydrocarbon" content. To determine whether such a relation existed, cores were taken ( 1) in an area where mortality had heen found to be low and (2) where mortality had been observed to be high. The Bay Chene Fleur area was chosen as representative of an area where the mortality was low. Two fourteen-month checks showed the oyster mortality to be about 30 percent at this station (Mackin and Wray, 1949, 1950) . At Sugar House Bend and Bayou Rigaud in lower Barataria Bay the losses had been similarly established ata level of approximately 80 percent in the same periods. Cores were taken in the general vicinity of each of these stations, and analyzed for unsaponifiable hydrocarbons. The data are presented in Table 14. TABLE 14 Unsaponifiable residues in muds from low and high mortality areas Unsaponifiable residue, percenl Depth core Pentane­ Compo~ile heavier Series of cores Top Middle Bollom percent Chene Fleur Station Area (annual mortality rate about 30 percent), October 18, 1947 to March 24, 1949 Ak 1-11 0.006 0.008 0.004 0.006 0.0000212 K 1-'ll 0.009 0.016 Bf 12..:22 0.005 0.005 0.006 0.006 0.0000007 Bg 12-22 0.005 0.016 0.0'24 0.012 0.0000021 Averages 0.006 0.011 0.011 0.008 0.0000080 Sugar House Bend and Bayou Rigaud (annual mortality rate about 80 percent), June 2, 1948, and November 18-19, 1949 Cl l-'11 0.017 0.018 0.011 0.007 0.0000019 Ag 1-11 0.009 0.015 0.007 0.004 0.0000051 Ag 12-22 0.015 0.010 0.009 0.006 0.0000068 Ck 12-22 0.003 0.003 0.004 0.002 0.0000009 Averages 0.011 0.011 0.008 0.005 0.0000037 With one exception all values in both high and low mortality areas were low. One composite sample in the low mortality area had a "pentane and heavier" fraction of about 0.2 ppm which could indicate the presence of petroleum hydrocarbons in small amount, although the "unsaponifiable hydroca.rbon" content was not above the average. On the whole, the data indicate that there was no significant difference in "hydrocarbon" content of the muds in the two areas. PETROLEUM HYDROCARBONS AROUND BLEEDWATER ÜUTLETS The studies presented above show that "hydrocarbons" found in muds of most areas where oysters grow are of plant origin. However, hydrocarbons of undoubted petroleum origin were found in muds in the vicinity of sorne oil field bleedwater outlets. Careful studies were made in and near oil fields in the marsh to the north, in fresh-water areas above the oyster-producing areas where mortality from pollution was claimed. Wherever indications of oil were found, the movement of hydrocarbons away from the effiuent outlets was traced, if possible. These studies showed that wherever large amounts of bleedwater were discharged into confining canals and bayous, there were considerable accumulations of oíl in the bottom muds. Depending on the degree of confinement of the bleedwater and the amount of the discharge, various degrees of pollu­tion occurred at the site of the discharge. Away from the point of discharge very rapid disappearance of the oíl took place. The heaviest concentration of oil at a bleedwater outlet was found in a canal at the LaFitte field. This area was studied closely. The LaFitte field is not in oyster-producing territory but is situated seven to eight miles to the northwest of Barataria Bay and about five miles from the nearest oyster-producing area. The point of bleedwater discharge was in an access canal, which in tum connects with Dupree Cut, a dredged channel running southeast through the marshes for about two and one-half miles. At its southeast end, Dupree Cut joins Bayou Cutler. Bayou Cutler then continues roughly to the southeast for another two and a half to three miles, to its juncture with Bayou St. Deni5. Oysters are grown in Bayou St. Denis. This bayou continues for another three miles to its junction with Barataria Bay. The relations are shown in Fig. 24. LaFitte is a large oil field and produced a large amount of bleedwater from the separators, all going into the access canal at Camp LaFitte. The average daily production was around 3000 barreis per day in the period 1941to1946 inclusive (Jensen 1948a). All of this entered the access canal at one point, referred to here as the "bleedwater outlet," or "BW outlet." It was assumed that net movement of the water was generally seaward and that dilution occurred as water from the access canal mixed with that in Dupree Cut and successively with each water body which added to the stream. Currents in Dupree Cut are feeble and dictated largely by wind (Lynch, 1948) . Lynch calculated that dilution of bleedwater with water in Dupree Cut reduced the concentration to less than 0.7 percent at the juction of the access canal with the cut. TABLE 15 "Hydrocarbon" content of cores taken al LaFitte Field and below in Bayou Cutler to Barataria Bay, August 13, 1947, to November 15·, 1949 Unsaponifiable residue, percenl Deplh in core Pentane and PosiLion, distance Composile Range heavier Series from bleedwaler source of cores of values Top M;ddle Bouom percenl Bb 1-31 At BW outlet in 2.526 2.244 to 0.0010300 canal al camp 2.819 Bv 1-37 At BW outlet in Q 1-10 canal at camp At BW outlet in canal 5.80 0.570 0.011 to 20.320 1.640 0.060 0.0014500 0.0004740 at Camp LaFitte 4.800 L38 75 ft below BW outlet in canal at LaFitte 0.041 0.0005930 L39 In canal al LaFitte camp warehouse, about 1400 ft below BW outlet 0.044 0.0000173 Cl Same 0.101 0.0001040 Am 12_:22 2% miles; junction of Dupree Cut and Bayou Cutler 0.007 0.006 to 0.016 0.04S. 0.008 0.005 0.0000044 Fi 1-7 J ust west of junction Dupree Cut and Bayou Cutler 0.033 0.024 to 0.048 E9 Junction Dupree Cut and Bayou Cutler ( west bank of bayou) 0.034 L 37 Near west bank of Bayou Cutler; 100 yards from junction Dupree Cut 0.012 0.0000040 Ch 1-11 200 yards down Bayou Cutler from junction with Dupree Cut 0.023 0.014 0.012 0.024 0.0000048 I 23 50 ft from east bank Bayou Cutler at junc­tion with Dupree Cut 0.011 0.017 0.009 Aq23-33 About 4~ miles S of BW outlet in 0.008 0.004 to 0.020 0.003 0.003 0.0000040 Bayou Cutler 0.014 I 22 About 4% miles S of BW outlet in Bayou Cutler, 45 ft from west bank 0.008 0.029 0.010 L36 5% miles from BW outlet; in Bayou Cutler ~mile above Bayou St. Denis 0.017 0.0000026 TAilLE 15--Continued "Hydrocarbon" content of cores taken at LaFitte Field and below in Bayou Cutler to Barataria Bay, August 13, 1947, to November 15, 1949 Unsaponi6able residue, percent Position, dislaoce Composile Range Depth in core Pentaoe and heavíer Series from bleedwater source of cores of values Top Middle Bottom percent Aq 12­22 5% miles from BW outlet above junction Bayou Cutler and B. 0.009 0.005 to 0.031 0.009 0.004 0.0000060 St. Denis in B. Cutler 0.014 121 5% miles from BW outlet at junction B. Cutler and B. St. Den is; 45 ft from east shore 0.010 0.003 0.010 E 1--0 5% miles from BW outlet at junction of B. Cutler and B.St. Denis 0.023• 0.016 to ................ Aq 1-11 opposite light Bayou St. Denis 1,4 0.032 mile helow junction with Bayou Cutler; 0.007 0.002 to 0.040 0.006 0.002 0.0000060 6 miles from BW 0.014 Ch 12-22 Bayou St. Denis just below junction B. Cutler; 6 miles L35 from BW outlet 7 +miles below BW 0.007 0.017 0.009 0.006 0.0000012 outlet B. St. Denis east bank at cut Ap 12­22 into Mud Lake 7 + miles below BW 0.016 0.013 0.006 to 0.025 ··--·--­0.014 0.011 0.0000006 0.0000117 outlet B. St. Denis 0.016 Ch23-33 8 miles from BW L34 outlet B. St. Denis 8 +miles from BW 0.028 0.044 0.013 0.011 0.0000058 outlet; west si de mouth of Mud Lake C2 75 ft from shore 8 + miles from BW 0.013 0.0000030 B. St. Denis south D 1-7 Mud Lake entrance 8 +miles from BW 0.028 0.0000033 outlet at south 0.010 0.008 to ···-········---- Ap 1-11 Mud Lake entrance 8 +miles below BW 0.036 B. St. Denis near 0.006 0.003 to 0.012 0.004 0.007 0.0000055 east side 0.008 Am 1-11 South shore of Mud Lake 8lf2 miles 0.013 0.007 to 0.086 0.020 0.009 0.0000024 from BW outlet 0.019 Wl-11 Mouth of B. St. Denis at North Pt. 9 0.013 0.007 to 0.010 0.006 0.023 0.0000022 miles below outlet 0.016 Ci 1-11 Mouth of Bayou St. Denis 9 miles below BW outlet 0.009 0.005 0.005 0.010 0.0000013 * Nol composite, bul mean of values for 6 cores . Table 15 shows the "hydrocarbon" content of muds in the access canal at the bleed-water outlet and at various points seaward to the junction of Bayou St. Denis with Barataria Bay. The first three sets of values given were from samples taken at the outlet. These show large amounts of extractives in the mud bottom in the canal at the point of discharge. Attention is called especially to the 10 cores of set Q1-10. The range of values in this circular pattern is remarkable (O.Oll to 4.800 percent). The depth core, that is, the one in which samples were analyzed at top, middle, and bottom, showed an even higher value in the surface four inches ( 20.320 percent). Attention is called to the "pentane and heavier" fractions reported for these three sets ( Bb, Bv, and Q) at the bleedwater outlet. This fraction averaged about 10 ppm. lt has been noted that the "pentane and heavier" fraction is more reliable than others in drawing a picture of relative amounts of petroleum hydrocarbons in the muds. Values of less than 0.1 ppm are found widely distributed in muds of Louisiana (Jensen and Potts 1953). Any values sensibly above 0.1 ppm may be taken to mean that petroleum oil is probably present, and if much higher than that figure it is nearly certain that such is the case. The "pentane and heavier" fractions at the bleedwater outlet ranged, approximately, from 5 to 15 ppm, probably indicating high levels of petroleum accumulation in the muds. The oil at the LaFitte bleedwater outlet showed very rapid decrease with distance away from the outlet. At 75 feet above 40 percent had disappeared, and at 1400 feet 94 percent reduction had occurred. These stations were in the access canal. At the lower end of Dupree Cut, the "hydrocarbon" values indicate that no measurable quantity of oil was present in the muds, and from there to Barataria Bay there is no indication of pollution as shown by the table. As a means of illustrating the disappearance of the oil with distance from the bleed­water outlet a table was compiled, based on thc values of the composite samples analyzed for "pentane and heavier" fractions. The value obtained by averaging the values of the three samples at the bleedwater outlet was rated at 100. The values of the sample at 75 feet, the two at 1400 feet, and the one at the junction of Dupree Cut with Bayou Cutler (2% miles distant, approximately) were calculated in percentage of the values at the bleedwater outlet. Table 16 shows the results. lt is not 'believed that the rapid reduction in amount with distance, shown in the table, resulted from dilution alone. In a canal like the access canal where the water move­ment is so weak as to be almost negligible, dispersa} by currents must be slow, a con­clusion borne out by the failure ( see section on hydrocarbons in water) to find sig­nificant amounts of oíl in the water or to find surface slicks at any significant distance from the outlet. Slicks are inevitable where oíl in quantity is carried by water, because of the low specific gravity of the oii. Y et a rough calculation from the values found in samples shows that not much more than 10 or 12 barreis of oíl were in the muds around the hleedwater outlet at any one time. But the bleedwater has discharged at this point for years, and it was apparent to the investigators that the total or cumulative amount of oíl was very much larger than that present at the time of sampling. In other words, it TABLE '16 Disappearance of oil in bottom muds with distance from bleedwater outlet at the LaFitte Field: "Pentane and heavier" fractions Distance of samples Percent oí hydrocarbons presenl from BW outlet based on a value of 100 al the outlet At BW outlet 100.00 75 ft from BW outlet 60.22 1400 ft from BW outlet 6.16 2Y2 miles from BW outlet 0.45 did not all accumulate; sorne oil disappeared in the course of time. The disappearance of oil is discussed in detail below. At other fields, concentrations of petroleum in muds at the bleedwater outlets were less than those found at LaFitte. At the Delta Farms field there was oíl in the muds of Bayou Perot and the "pentane and heavier" fractions showed that there was a low-level persistent pollution extending to the lower limits of the southerly parts of the severa! small oil fields, elements of which extend for 21/2 miles along Bayou Perot. Below this area, "hydrocarbons" in amounts attributable to petroleum contamination were not found. The data are presented in Table 17. No part of the Delta Farms field is in or near oyster-producing territory and Bayou Perot is nearly fresh water. The locations of the samples listed in Table 17 are presented in Fig. 25. At the Lake Hermitage field in the fresh-water marshes to the northeast of Barataria Bay, no bleedwater was produced in the period 1941 to 1947, and there were only two producing wells in 1947. The amounts of "hydrocarbons" found in muds in this field are presented in Table 18. These values should be compared with those of oyster­producing areas of Barataria Bay (Table 25). The locations of these samples are shown in Fig. 26. At the English Bay field, which is in oyster-producing territory, only one set of cores among the many taken indicated that there were probably petroleum hydrocarbons in the muds. This set (Ce 1-11) was taken in a company canal roughly 400 to 500 feet from the bleedwater burning pit. Other cores, including those taken much closer, showed "unsaponifiable hydrocarbon" and "pentane and heavier" fractions so low that they must be considered to be negative for petroleum. Cores were taken at varying distances from the bleedwater burning pit into and across English Bay to the east, but no indi- TABLE 17 "Hydrocarbons" in muds in Bayou Perot in and below the Delta Farms Field August 13, 1947, and August 17 and 31, 1948 l:nsaponifiable residue, perceot Depth in core Penlane and Approximate distance from Composite Range heavier Series nearesl well or BW outlet of cores of \·alues Top Middle Bottom perceol At34-44 Zero (in canal from main field) 0.066 0.048 to 0.109 0.0000043 HumbleCo. 0.289 At 23-33 Zero at bleedwater outlet T.T. Co. 0.046 0.021 to 0.079 0.106 0.072 0.005780 Delta Farms Field 0.825 At 12-22 About Vi; mile 0.080* 0.003 to 0.026 0.069 0.077 0.0000096 below nearest well 0.300 At 1-11 1 mile below field 0.033 0.023 to 0.023 0.042 0.053 0.0000108 0.078 Ar34-44 2 miles below field 0.045 0.041 to 0.059 0.0000123 0.059 Ar 23­33 2lf2 miles below field 0.086 0.002 to 0.002 0.012 0.005 0.0000039 0.025 Ar 12-22 3lf2 miles below field 0.027 0.009 to 0.050 0.018 0.009 0.0000052 0.050 Ar 1-11 4 miles below field 0.002 0.006 to 0.015 0.005 0.009 0.0000029 0.015 C3 5 miles below field 0.036 0.0000032 * Not a composite, for which data were lost, but mean of all cores except the one reserved for depth analysis. F1c. 25. Locations of cores taken for "hydrocarbon" analysis in Bayou Perot, at the Delta Farms and Little Temple oíl fields. cation of pollution was found in these. Table 19 reports the "hydrocarbon" values found in making this study. The Iocations where core samples were taken for "hydrocarbon" measurement in the English Bay field are shown in Fig. 26a. The conditions at the Lake Barre Field of the Texas Company above Terrebonne Bay deserve special comment because this was the site of extensive studies on the effect of bleedwater on oysters which are reported in another section. Here oysters grow well even under the well rigs and on the pilings of the cat walks and the bulkheads. Employees of the Texas Company regularly pry these oysters loose and use them for food. They are generally very good oysters when fat in winter. Sorne oysters grow within a few feet of the bleedwater outlets, but they are noticeably less in number here. As stated above, bleedwater production at the Lake Barre field averaged 6603 barreis per day, with a maximum production of 9120 barreis per day. This bleedwater is dis­charged through two outlets set within a few feet of each othei-. The discharge is into relatively open water. There is no land within miles toward the north, and only little land in any direction. The only nearby "land" is in the form of broken-up marsh islands. The data show that the mud samples taken at the bleedwater outlet at Lake Barre almost certainly contained sorne petroleum hydrocarbons (Table 20). However, the "pen­tane and heavier" fractions showed only 1.17 ppm in the circular pattern of cores at TABLE 18 Unsaponifiable residues of muds in and around the Lake Hermitage Field. Ali distances are approximations in nautical miles. October 18, 1947, to August 4, 1949 Unsaponi6able residue, percenl Location and distance from separators (Note : no BW Composite Depth core Pentane and beavier Series produced bere; only d.istillate) of cores Top Middle Bottom percent Be 12-22 Junction of Wilkinson and Hermitage Bayous; in field 0.053 0.070 0.113 0.026 0.0000034 Be 1-11 Bayou Wilkinson at end of canal from separator 1250 ft from BC 12 0.014 0.040 0.009 0.009 0.0000020 Be 23-33 Bayou Wilkinson at junction Racquette Bayou 1.7 miles below separator 0.016 0.038 0.017 0.024 0.0000021 Bdl-11 Wilkinson Bayou 1.8 miles below separator 0.021 0.025 0.008 0.015 0.0000019 Bd 12­22 Upper Petit Bay Chene Fleur; 2 miles from separator 0.008 0.029 0.017 0.010 0.0000023 Bd 23-33 Wilkinson Bayou; about 2.7 miles below separator 0.016 0.038 0.017 0.024 0.0000021 Be 1-11 Wilkinson Bayou ; 3 miles below separator 0.016 0.008 0.015 0.010 0.0000016 Be 23-33 Be'l2-22 Wilkinson Bayou; 31,4 miles below separator Wilkinson Bayou ; % mile below separator 0.012 0.008 0.038 0.005 0.020 0.011 0.016 0.013 0.0000025 0.0000006 Bt l'-11 Wilkinson Bayou; 3.6 Bt 23­33 miles below separator Upper Bay Chene Fleur at 0.013 0.009 0.015 0.009 0.0000011 junction with N. Bayou; 3.8 miles below separator 0.005 0.005 0.006 0.006 0.0000007 Bt 12­22 Ak 1-11 Bay Wilkinson 4.5 miles below separator Southern part of 0.022 0.035 0.029 0.0000032 Wilkinson Bay; 5.8 miles below separator 0.006 0.008 0.004 0.006 0.0000212 K 1-11 Wilkinson Bayou; 6 miles below separator 0.009 0.016 Bg 12-22 Wilkinson Bayou ; 6.5 miles below separator 0.012 0.008 0.009 0.006 0.0000032 the bleedwater discharge, and at 50 feet south only 0.12 ppm. At greater distances there was no indication that petroleum hydrocarbons were present in the muds. The locations of these samples are shown in Fig. 27. The great difference in the concentration of petroleum hydrocarbons at Lake Barre and at LaFitte is due to the fact that at Lake Barre the efHuent passes into relatively open water with positive tidal current movement and a great expanse of moderately saline water for dilution. The effect of burning pits is shown by studies at the Venice field of the Tidewater Oíl Company. This field is situated far clown the Mississippi Delta in nearly fresh water. It is also in the marsh and in a system of confining canals. A number of burning pits evaporate or bum hydrocarbons in the bleedwater from the separators. Excess salt water from the pits drains into the canals. An extensive series of mud samples strategi­cally distributed around the entire field failed to show contamination with petroleum hydrocarbons from bleedwaters (Table 21). Fig. 28 shows the locations of samples listed in Table 21 which were taken in and around the Venice oíl field­ FrG. 26. Locations of cores taken for "hydrocarbon" analysis in Lake Hermitage field and southward. At Caillou Island and Lake Pelto fields in lower Terrebonne Bay a different situation exists. Both fields are located in wide open water of high salinity. Bleedwater is dis­charged into the water directly. Cores taken at these bleedwater outlets failed to show any contamination of the muds within a few feet of the points where effiuent was dis­charged. At Lake Pelto the bleedwater discharge averaged 1385 barreis per day from June 1, 1947, to June 1, 1949. At Caillou Island in the same period the average bleed­water production was about 5072 barreis daily. A large pass to the open Gulf is between and near these two fields, insuring a short flushing period. The values of the unsaponifi­able residues for the Lake Pelto field are shown in Table 22, and those for Caillou Island in Table 23. Fig. 29 shows the locations of samples taken in the Lake Pelto field and Fig. 30 shows the locations of the samples in the Caillou Island oíl field. F1G. 26a. Locations of cores taken for "hydrocarbon" analysis in the English Bay field and adjacent areas. TABLE 19 Unsaponifiable residues of muds at varying distances from the bleedwater burning pit in the English Bay Field, January 3, 1948 and October 21, 1949 Lnsaponifiable resídue, percent Depth in core Penlane and Composite heavier Location; dislance from BW oullet ol cores Top Middle Botlom percent In canal 100 ft from BW burning pit 0.037 At mouth of canal from BW pit, 300 ft 0.032 ü.0'29 0.025 0.013 0.0000040 J ust N of intersection of canals, 4-500 ft N of BW pit 0.048 0.258 0.023 0.057 0.0000615 In canal at "Y" ;f; mile east of BW pit 0.036 0.046 0.054 0.022 0.0000021 About ~mile from BW pit in canal to NE 0.047 About 1h mile E and S of BW pit; 0.052 0.080 0.033 0.0000071 west margin of English Bay About Vz mile E of BW outlet in west 0.011 0.009 0.010 0.006 0.0000017 side of English Bay Vi mile from BW outlet at mouth of canal 0.010 0.015 0.008 0.011 0.0000022 at west margin of English Bay 0.013 0.025 0.021 0.008 Ahout 1 mile from BW outlet; east margin of English Bay 0.009 O.Ol'l 0.008 0.021 0.0000023 About 1 mile from BW outlet; northeast English Bay, in outlet to Bayou August 0.015 0.014 0.010 0.012 0.0000044 About l~ miles from BW pit; southwest English Bay 0.015 0.009 0.012 0.017 0.0000016 About lYz miles from BW outlet ; south part of English Bay 0.012 0.CH4 0.014 0.011 0.0000048 About IV:! miles from BW outlet; south part of English Bay 1Vz miles SW of BW outlet in 0.013 0.018 0.016 0.013 0.0000015 Bayou Fontanelle 0.018 0.0'21 0.019 0.015 0.0000027 TABLE 20 Unsaponifiable residues of muds at and around the bleedwater outlets at the Lake Barre Oil Field, December 22, 1947, September 1, 1948, and March 29-31, 1950 Unsaponifiable residue, percenl Series Location Composite of cores Range of values Top Deplh in core Middle Bottom Penlane and heavier percent -------·· (Hopkins) At BW outlets 0.183 p 13-22 At BW outlets 0.048 0.0'20 to 0.0001170 0.159 · Au 7-17 40 to 50 ft S of 0.023 0.002 to 0.003 0.008 0.002 0.00001 20 BW outlet 0.051 Cw22 In channel ~ mile S 0.0000011 Cu 77 In channel 11,4 miles S of BW outlet 0.0000051 p 23-33 2% miles NW at 0.022 0.008 to 0.057 0.016 0.012 0.0000056 entry to Lake Felicity 0.032 F1c. 27. Locations of cores taken for "hydrocarbon" analysis (1 ) in the area of the Lake Barre Oil Field, (2) in Little Lake. TABLE 21 Unsaponifiable residues of extractives of muds near burning pits and in the canals of the Venice Oil Field, February 21-23, 1950 Unsaponifiable residue, percenl D epLh in core Penlane and Composite heavier Series of cores Top Middle Bottom percent Cr34-43 0.018 0.010 0.011 0.022 0.0000017 Cr23-33 0.018 0.032 0.007 0.007 0.0000045 Cr 12-21 0.03'2 0.073 0.021 0.013 0.0000026 Cr l-'10 0.017 0.057 ü.0'25 0.017 0.0000032 Cs 12-21 0.009 0.006 0.009 0.007 0.0000032 Cs 1-11 0.008 0.007 0.005 0.002 0.0000028 Ct 12-21 0.008 0.009 0.012 0.006 0.0000022 Ct23-32 0.008 0.011 ü.0'12 0.015 0.0000057 Ct 34-43 0.011 0.014 0.007 0.007 0.0000031 FrG. 28. Canals of the Venice oil field and locations of cores taken for "hydrocarbon" analysis in and around this field. TABLE 22 Unsaponifiable residues of the muds around the bleedwater outlets at the Lake Pelto Oil Field, November 3-16, 1947, October 5, 1948, and March 30, 1950 Unsaponifiable residue, percenl Deplh in core Penlane and Composite heavier Series Location of cores Top M;ddle Bottom percenl Ao 1-11 At BW outlet 0.003 0.00'2 0.002 0.002 0.0000025 Cv44 200 ft N of BW outlet 0.0000043 Cv33 200 ft E of BW outlet 0.0000032 Cv22 200 ft S of BW outlet 0.0000054 Cv11 200 ft S of BW outlet 0.0000046 N 1-8 1670 ft E of BW outlet 0.016 Cv66 4000 ft NW of BW outlet 0.0000033 o 1-11 4700 ft NE of BW outlet 0.013 0.006 0.006 0.005 0.000004'2 o 12-22 4700 ft NE of BW outlet 0.016 0.008 0.005 0.009 Cv45-55 3 miles WNW of BW outlet 0.0000032 71 TABLE 23 Unsaponifiable residues of muds around the bleedwater outlet at the Caillou Island Oil Field, August 5, 1948, July 20, 1949, and March 29, 1950 Unsaponifiable r esidue, percenl Deplh in core Pentane and Composite h e avier Series Location of cores Top Middle Bottom percenl Cu 1-11 At BW outlet 0.009 0.012 0.008 0.009 0.0000065 Ao 12-22 At BW outlet 0.004 0.011 0.003 0.003 0.0000043 Cu23-33 200 ft 'S of BW outlet 0.006 0.017 0.005 0.004 0.0000058 Cu 45-55 200 ft N of BW outlet 0.007 0.009 0.008 0.010 0.0000037 Cu 12-22 200 ft E of BW outlet 0.005 0.011 0.006 0.006 0.0000030 Cu 34-4:4 200 ft W of BW outlet 0.006 0.012 0.006 0.006 0.0000059 Cu 56-66 %mile from BW outlet at outlying well 0.016 0.012 0.015 o.cm 0.0000039 Br 12-22 2 miles from BW outlet* 0.014 0.008 0.015 0.007 0.0000028 • Near a small outlying island. \..¡:..\(.t.. PELTO FfcLo NOTE : 1 ---------­All w•ll' 1hown •r: T. T. ~'j>/' •"' "-.\ -, ---if------129•06'l--+-------===1-+-+-----.l\:~------+-.~-,;-.;.--+--.;. .,, ... ... 90 "39 9~42 F1G. 29. Locations of cores taken for "hydrocarbon" analysis in the Lake Pelto field. The Bay Ste. Elaine field is spread over a considerable area of small bays, bayous, and dredged channels in the area just to the west of Terrebonne Bay. Most of the wells are in marsh. Bleedwater production for the entire field in 1947 to 1949 averaged 258 barreis per day. There are two major parts to the field; the one centering around the camp above and below Bay Coon Road and the other lying to the north in the marshes. The cores taken were from the more southerly arca. Ali of the corings were in the field and ali were relatively near oil wells, storage tanks, or separators, etc. However, the Au and P series of Table 24 were taken near the bleedwater outlets at the Bay Ste. Elaine camp, and were on the site where an oil loss had occurred. The locations of the mud sam­ Frc. 30. Locations of cores taken for "hydrocarbons" analysis in the Caillou Island field . TABLE 24 Unsaponifiable residues of muds in the Bay Ste. Elaine Oil Field, December 22, 1947 to September 1, 1948 Unsaponifiable residue, percent Deplh in core Penlane and Composile Range heavier Series of cores of values Top Middle Bottom percenl Au 1 0.018 0.040 0.063 Au2 0.135 0.023 0.060 Au3 0.080 0.025 0.310 Au4 0.021 0.046 0.045 Au5 0.087 0.024 0.055 Au6 ... 0.058 0.028 0.047 ···-· p 1-1'2 0.036 0.016 to 0.064 0.054 0.079 0.010 0.0000107 Ad 1-10 0.018 0.016 to 0.035 0.049 0.067 0.005 0.0000071 Ae 1-10 0.029 0,015 to 0.033 0.040 0.010 0.006 0.0000041 Ae 12-22 0.026 0.015 to 0.035 0.035 0.054 0.003 0.0000071 Ae'23-32 0.030 0.013 to 0.036 0.005 0.044 0.003 0.0000065 Ae34-43 0.034 0.005 to 0.037 0.064 0.195 0.005 0.0000064 Aa 1-10 0.011 0.009 to 0.015 0.055 0.008 0.009 0.0000021 Aj 23-32 0.015 0.010 to 0.015 0.014 0.012 0.007 0.0000158 Aj 12-22 0.010 0.004 to 0.014 0.010 0.009 0.004 0.0000185 Aj 1-10 0.006 0.005 to 0.009 0.008 0.010 0.010 0.0000225 Aj 34-44 0.017 0.008 to 0.017 0.015 0.013 0.004 T 13--'22 0.016 0.007 to 0.036 0.043 0.010 0.0000014 T 1-10 0.019 0.015 to 0.065 0.157 0.020 0.041 0.0000053 T 24-33 0.014 0.013 to 0.031 0.031 0.005 0.005 0.0000096 u 1-10 0.043 0.016 to 0.045 0.058 0.014 0.016 0.0000076 u 12-22 0.027 0.009 to 0.052 0.081 0.019 0.007 0.0000030 y 12-22 0.011 0.005 to 0.044 0.016 0.009 0.016 0.0000019 y 1_:10 0.014 0.007 to 0.024 0.049 0.043 0.009 0.0000015 z1-10 0.018 0.012 to 0.021 0.038 0.007 0.007 0.0000026 z12-22 0.028 0.014 to 0.042 0.056 0.045 0.013 0.0000053 ples taken in the Bay Ste. Elaine field are shown in Fig. 31. Sorne of the data contained in Table 24 are also contained in Table 13, which shows values for cores taken in the marshes (see previous discussion). These data show that there were two local areas of contamination. The first of these was the Bay Ste. Elaine camp itself, where there is a bleedwater discharge, a tank bat­tery, and an oil loading dock, in addition to the wells, and where a local petroleum loss had been sustained. The other contaminated area was in the canals and mud bottom of Bay Coon Road ( the Aj series). This series is very interesting in that the detection of petroleum contamination depended on the "pentane and heavier" fraction. The pollution shown here is not considered very significant because the composite values and range of values of the non-volatile fractions were low. The Au series ( taken where oil spillage occurred) showed sorne spots of oil pollution, as indicated by values for "unsaponifiable hydrocarbons", or unsaponifiable residue of extracted material. Most corings in the Bay Ste. Elaine field showed no pollution, but most did show the effect of peaty layerings in the marshes and along the margins of small bays and bayous. Many oyster experiments were carried out in the Bay Ste. Elaine field (Menzel and Hopkins, 1953). Oysters grow naturally there. HYDROCARBONS IN THE BoTTOM Muos oF BARATARIA BAY Data on the concentrations of hydrocarbons in muds around bleedwater outlets have been presented in detail. At sorne points there was undoubtedly petroleum incorporated in the mud and in sorne others none was found. lt was desirable to compare the values associated with bleedwater outlets with values in the oyster-producing areas. Greater Barataria Bay was selected for test since the claims of oystermen indicated that this was the area of greatest loss of oysters. Samples taken near the Queen Bess tank battery are included in this table, since bleedwater production here was never more than a trickle and was shut off completely about the time these cores were taken. About 650 cores, in 68 series, were taken in the Barataria Bay area (Table 25). No TABLE 25 Unsaponifiable residues of muds in the Greater Barataria Bay area, August 12, 1947, to February 17, 1950 Vnsapooi6ahle residue. percent Depth in core Pentane and Compo&ite hea1•ier Localion of cores Top Middle Bottom percent Hackberry Bay 0.007 0.017 0.009 0.008 o. 000002 4 Hackberry Bay 0.006 0.017 0.009 0.014 0.0000022 Hackberry Bay 0.007 0.007 0.004 0.005 0.0000027 Hackberry Bay 0.006 0.024 0.018 0.005 0.0000026 Hackberry Bay 0.0000044 Hackberry Bay-south part 0.003 0.005 0.007 0.003 0.0000039 Creole Bay--east entrance 0.017 0.011 0.008 0.043 0.0000020 Creole Bay--east entrance 0.0000035 Barataria Bay-midwest 0.010 0.011 0.030 0.004 0.0000025 Barataria Bay-midwest 0.0000035 Barataria Bay-west side 0.001 0.006 0.003 0.002 0.0000040 Barataria Bay-west side 0.0000037 Barataria-west side 0.008 0.010 0.003 0.005 0.0000099 Barataria-just north ofBassa entrance 0.006 0.017 0.008 0.004 0.0000031 Bassa Bassa Bay 0.0000035 At Bassa Station 0.006 0.009 0.007 0.006 0.0000023 At Bassa Station 0.005 0.004 0.004 0.005 0.0000038 Bassa Pass, south en trance 0.011 0.004 0.016 0.004 0.0000116 W. Barataria, off Mendicant Islands 0.006 0.008 0.006 0.008 0.0000022 W. Barataria, 300 ft north of Queen Bess BW outlet 0.007 0.003 0.000 0.004 0.0000022 W. Barataria, 300 ft west of Queen Bess 0.003 O.Oll 0.004 0.003 0.0000025 W. Barataria, 300 ft east of Queen Bess 0.004 0.006 0.000 0.003 0.0000032 W. Barataria, 300 ft south of Queen Bess 0.008 0.029 0.003 0.004 0.0000029 Sugar House Bend, south Barataria Bay 0.003 0.003 0.004 0.002 0.0000099 Mouth Bayou Rigaud 0.015 0.010 0.009 0.006 0.0000068 Lab. in Bayou Rigaud 0.017 0.018 0.011 0.007 0.0000019 Bayou Rigaud Sta. 0.009 0.015 0.007 0.004 0.0000051 South Caminada, near Chinatown dock 0.005 0.006 0.004 0.004 0.0000096 Terminus of Southwest La. Canal, east end 0.009 0.028 0.005 0.005 0.0000151 Mouth, Bayou St. Denis 0.013 0.010 0.006 0.023 0.0000022 Mouth, Bayou St. Denis 0.009 0.005 0.005 0.010 0.0000013 North of St. Den is light: near shore, west outlet, Wilkinson Canal 0.009 0.017 0.007 0.003 0.0000214 End of Wilkinson Canal at west outlet 0.012 0.022 0.021 0.026 -.... ···-· Mouth of Wilkinson Canal: east outlet 0.006 0.014 0.008 0.005 0.0000029 West outlet of Wilkinson Bayou 0.008 0.023 0.003 0.004 0.0000113 West of outlet of Wilkinson Canal 0.008 0.016 0.006 0.021 ····--­--------­ TABLE 25-Continued Unsaponifiable residues of muds in the Greater Barataria Bay area, August 12, 1947, to February 17, 1950 Unsaponifiable re&idue, percenl Dcpth in core Pentane and Composite heavier Localion of cores Top Middle Bollom percent St. Mary's light 0.008 0.017 0.010 0.007 0.0000025 St. Mary's Point 0.007 0.017 0.009 0.005 ------.-·· -·-· St. Mary's Point 0.007 0.016 0.007 0.010 0.0000014 Mouth, Grand Bayou 0.015 0.020 0.020 0.007 0.0000088 Mouth, Grand Bayou 0.009 0.011 0.005 0.008 0.0000040 Saturday Island 0.012 0.012 0.003 0.004 0.0000010 Bayou Cooper, east side of Bay 0.013 0.012 0.011 0.012 0.0000034 Lower Bay Ronquille 0.003 0.0ll 0.0ll 0.006 0.0000045 Lower Bay Ronquille 0.010 0.020 O.Oll 0.011 0.0000017 Southeast Barataria Bay 0.006 0.006 0.005 0.004 0.0000105 Middle of Bay Long 0.029 0.010 0.010 0.007 0.0000027 Middle of Bay Long 0.009 0.008 0.009 0.017 0.0000036 Middle of Bay Long 0.013 0.006 0.016 0.007 0.0000032 Middle oí Bay Long 0.011 0.015 0.004 0.005 0.0000058 Middle of Bay Long 0.010 0.012 0.009 0.010 0.0000040 Middle of Bay Long 0.013 0.015 0.016 0.010 0.0000024 Ronquille Pass (to Grande Ecaille) 0.022 0.022 0.005 West Grande Ecaille 0.009 0.009 0.017 0.005 0.0000015 Southeast Grande Ecaille 0.007 0.007 0.005 0.0000035 Southeast Grande Ecaille 0.014 0.024 0.019 0.009 0.0000026 Southeast Grande Ecaille 0.013 0.037 0.007 East Grande Ecaille 0.012 0.045 O.Oll 0.099 Northeast Grande Ecaille, Mouth, Rattlesnake Bayou 0.028 0.062 0.007 0.099 0.0000031 Mouth, Rattlesnake Bayou 0.022 0.017 0.078 0.012 Big Island, northeast Barataria 0.017 0.023 0.032 0.012 0.0000035 Northeast Barataria: Entry Bay Baptiste 0.008 0.023 0.012 0.004 0.0000045 N ortheast Barataria 0.008 0.147 0.003 0.003 0.0000025 Northeast Barataria 0.015 0.037 0.086 0.073 0.0000044 Northeast Barataria 0.013 0.074 0.036 0.006 0.0000042 Northeast Barataria, near Ornes Camp 0.010 0.014 0.008 0.014 0.0000024 Northeast Barataria 0.016 0.01'2 0.054 0.006 0.0000012 place where there was certain contamination of the bottom was found, but pollution was suspected at severa! isolated spots. The first of these was in the end of the Southwest Canal, where the "pentane and heavier" was high. At that point boat and barge traffic is always heavy. At the south pass to Bassa Bassa Bay, the "pentane and heavier" frac­tion was possibly a little high. Again, at the end of the west outlet of Wilkinson Canal. the "pentane and heavier" was definitely high, as shown by two core series. lt is probable that these local concentrations at the ends of canals with heavy boat traffic are due to the relatively faster currents in the channels. Oíl from boats and bilge is adsorbed on silt which is deposited when the current rate drops on entering a hay. With the exception of the three places to which attention is called, no other part of the Barataria Bay area showed "hydrocarbon" in muds in concentrations large enough to indicate that pollution exists. The values of "hydrocarbons" found in muds of this area, where oyster losses were claimed to be greater than for ali other areas combined, were generally low. The values in Table 25 should be compared with those of control samples in Table 10. HYDROCARBONS IN WATER Numerous determinations of hydrocarbons in bleedwater were reported by Jensen (1950). The amounts of oil contained in bleedwater vary widely depending on efficiency in separation of salt water from the oil. Jensen reported up to 931 ppm of "non­volatile hydrocarbon" in sorne bleedwaters produced in southern Louisiana, and as low as 3 ppm in others. Those bleedwaters containing high amounts of oil are usually burned in Aare pits or disposed of in sorne manner not involving discharge into natural waters. Of those discharged into open water, the highest "hydrocarbon" content was 226 ppm at the Caillou lsland field. Of 60 determinations, involving 23 bleedwaters, and using from one to three methods of extraction of each bleedwater, the mean value was 35 ppm. Only five out of 60 determinations using thret methods showed more than 100 ppm of "hydrocarbons" in bleedwaters. Sin ce sorne methods of extraction (Jensen, 1950) remove substances other than hydrocarbons from the water samples, the actual mean hydrocarbon content must have been less than 35 ppm. To determine what effect bleedwaters have on the amounts of "hydrocarbons" found in water around the bleedwater discharges, severa! studies were made. Data on these are contained in Table 26. This table shows that the bleedwater has almost no effect on the "hydrocarbon content" of natural waters. Even as close as 25 to 50 feet from bleedwater discharge sites, "hydrocarbon" values were less than that of a control site in the eastern St. Bernard Parish marsh, east of the Mississippi River. Other controls showed low levels of TABLE 26 Concentrations of "hydrocarbons'" in bleedwater and around bleedwater discharge sites at severa) oil fields as compared with "hydrocarbons" at great distances from bleedwater discharge areas ..Non-volatile HCº. Loeation of samples :\'oll method, ppm Lafitte Oil Field {8-15-47) BW discharge site in canal 5.2 Near BW discharge in canal 2.0 Canal 1400 feet from BW discharge 2.6 Canal in oil field 1.4 Mud Lake, about 6 miles below BW outlet 2.6 Mud Lake, 6--7 miles below BW outlet 3.5 Lafitte Oil Field (10--19--47) BW outlet at Camp Lafitte 3.6 75 feet from BW outlet 1.8 1400 feet from BW outlet 3.8 Bayou Cutler about 3 miles below BW outlet 2.4 Bayou Cutler, 5 miles below BW outlet 2.0 Bayou St. Denis, 5.5 miles below BW outlet 1.4 Mud Lake, 6--7 miles below BW outlet 1.4 Delta Farms Oil Field (3-25-49) Bleedwater, Delta Farms 5.0 25 feet south of BW discharge 4.0 50 feet south of BW discharge 1.6 200 feet south of BW discharge 3.2 500 feet south of BW discharge 2.4 Delta Farms Oil Field (4-27-49) Bleedwater, Delta Farms 7.6 25 feet south of BW discharge 0.6 50 feet south ofBW discharge 1.0 200 feet south of BW discharge 0.8 500 feet south of BW discharge 1.6 Halfmoon Lake (East of Mississippi River; control) 1.0 "hydrocarbon" everywhere in Louisiana marsh waters. For example, three samples from marsh ponds showed 0.7, 0.8, and 1.25 ppm respectively. Two samples of water from aquarium supply waters at the Grand lsle Laboratory showed 0.8 and 3.6 ppm. Owen (1955) attempted to determine whether ether-soluble compounds of the natural waters of Louisiana oyster-producing bays and bayous differed in high mortality areas as compared with those of low mortality arcas. His data show no difference in the concentrations, paralleling his findings when comparing the extracts of muds in the same areas. The amounts reported by Owen were very much less than those found by Jensen. He also reported the results of the analysis of samples collected by Louisiana Coastal W aste inspectors. Sorne of these analyses showed very high concentrations of oíl, but Owen pointed out that these cases of high content resulted from taking samples from seepages from oíl lines, waste pits, etc., and when compared with his own random sarnpling, they proved the great extent of dilution. Sorne of the samples taken by Coastal W aste inspectors and showing high oíl content were from areas far removed from the oyster-producing bays. STUDIES OF DILUTION OF BLEEDWATER Hewatt (1950) made a series of studies to determine how rapidly bleedwater became dispersed and diluted with distance away from discharge points. He pointed out that the highly concentrated bleedwater brines generally contained salts in concentrations of over 100 ppt. The rate of dilution could therefore be approxirnated by measuring salinity at the bleedwater discharge and at varying distances away from it. For measuring salinity Hewatt used (1) the usual titration method, ( 2) complete analysis for salts, and (3) a resistivity or conductivity machine. He studied dilutions in this manner at seven different oil fields, sorne in brackish water and others in oyster-producing areas. Hewatt made four separate studies at the Lake Salvador oil field. This field produces bleedwater varying from 107 to 131 ppt salinity. The normal salinity of the water in Lake Salvador varíes from about 0.1 to 0.25 ppt. Hewatt was unable to trace the effect of the bleedwater farther than 200 feet. He calculated that the greatest possible concen­tration of bleedwater which could be in the lake was one part in 1892 of water if only the rainfall which fell on the lake was considered. The actual dilution would be enor­rnously greater. This field produced about 2415 barreis of bleedwater daily in 1949. At the LaFitte field the bleedwater is emptied into a narrow canal which leads into Dupree Cut, another dredged channel which ultimately connects with Barataria Bay. On January 24, 1947, Hewatt found that the salinity of the bleedwater was 128 ppt. At that time the field was producing about 8949 barreis daily (January, 1947, only). At about 1400 feet below the outlet Hewatt found that the salinity had dropped to 1.49 ppt and at 500 feet to the north and to the south in Dupree Cut, the salinity had dropped to about 0.5 ppt. Normal salinity in that area varíes from about 0.3 to 10.0 ppt, depending on local rainfall and tidal conditions. Hewatt repeated these observations on February 8, 1947, with almost identical results. On February 23, 1947, he found that at 24 feet from the bleedwater outlet salinity was reduced to 2.81 ppt. Hewatt made severa! other studies at the LaFitte field. AII of these showed that dilution was extremely rapid, and all showed that mixing was complete and thorough, stratification occurring only within the canal into which the bleedwater outlet ernptied. His conclusions were confirmed at other oíl fields, i.e., that thorough mixing always took place. Hewatt studied dispersa! of bleedwater at the Lake Barre oil field above Terrebonne Bay. Continuous records here have shown that the salinity remained near 20 ppt for most of the time. Oysters grow well in this field attached to pilings and even on the mud beneath the wells. Bleedwater was discharged through two "gun barreis" placed close together (20 feet apart) , in the amount of 3590 barreis daily during February, 1947. On February 27, 1947, Hewatt found sorne stratification of salinity as far out as 60 feet from the point of discharge. Salinity of bleedwater was titrated at 149 ppt. Maximum salinity recorded by him on the bottom within 60 feet was 23.5 ppt when his control area showed 20.5 ppt. Hewatt repeated these studies in February of 1948 with almost identical results, and made other studies at later dates at this oil field. He found thorough mixing of the bleed­water and rapid dilution at all times. At the English Bay field he found a slight increase in salinity in the water of a short canal into which bleedwater emptied, but no change in salinity outside of it. Later he failed to find any change in salinity following a slight modification in disposal method. A fiare is used at the bleedwater pit at this field. At the Venice field, where a number of fiare pits are used, Hewatt found no trace of increased salinity in any of the company canals. At the Leeville field he found salt incorporated in the mud of the bottom, and increased salinity in parts of a small reservoir, but no indication of stratification outside oí the reservoir. His final conclusion was that thorough mixing of the bleedwaters with surrounding waters took place within a short distance. CALCULATIONS oN D1LUTION oF PoLLUTANTS Owen (1955) made sorne calculations designed to give sorne idea of dilutions of crude petroleum and bleedwater, and the amounts necessary to make a "one percent soluble fraction" of oil in the bays. Owen had concluded from experiments that a "one percent solution" was "detrimental" to oysters when made up in the manner used in his studies. See experimental section that follows. According to Owen's calculations 767,490 barrels of crude petroleum would be required in a hay 5 miles wide, 10 miles long, and 5 feet deep. This approximates the size of Barataria Bay proper. Owen also calculated that the amount of bleedwater required to make a one percent solution of "soluble fraction" of oil in such a hay was about 3.8 billion barreis, and that with a production rate of 50,000 barrels of bleedwater daily it would require 210 years to build up to that amount. Owen did not consider flushing of his hypothetical hay, but treated it as a closed body. Jensen ( 1950) gathered data on the amounts of bleedwater produced in oil fields of southern Louisiana. He used these figures to make calculations designed to show what were the maximum possible concentrations of bleedwaters and crude oils in Barataria Bay. He pointed out that for various reasons it was impossible to calculate exact con­centrations in the bays, but that by making certain conservative assumptions, he could arrive at figures which were certainly higher than the actual values. The results of Jensen's calculations are tabulated below: ( 1) Greatest possible increase in salinity in Barataria Bay due to bleedwater ____ _______ --------------------------------------------------------·--· --0.00037 ppt (2) Greatest possible change in the magnesium-calcium ratio of the sea water in Barataria Bay dueto bleedwater ________ __ ____ _________ __ ___ _ 0.00000952 (3) Greatest possible concentration of petroleum hydrocarbons in hay waters due to bleedwater ------------------------------------------------------0.000062 ppm (4) Assuming that the oil companies lost 5,000,000 barreis of crude oil per year, this would produce a concentration in Barataria Bay waters of --------------------------------------------------------------------------------6.25 ppm ( 5) Assuming that 5,000,000 barreis of crude petroleum was lost in one year and ali of it was incorporated into the top 4 inches of mud on the bottom, the concentration would be --------------------------0.85 percent Both the calculations by Owen and those by Jensen assumed that bleedwater and oil must have been distributed over all of the area of Barataria Bay. Research Foundation studies showed that oyster mortalities occurred in all areas. They were not at the same rates everywhere, but in Barataria Bay tended to increase with distance from the oil operations because most oil operations were in brackish-water areas above the bays and the rate of oyster mortality increased with increasing salinity. Concentrations of bleedwater and oil in a hay may never be the same over an entire hay. Hewatt's studies showed that dilution of bleedwater was rapid and complete, and the concentrations must decrease by at least the square of the distance away from the point of discharge. Crude oil losses, on the other hand, are unevenly distributed in both space and time, and oil may be concentrated within certain areas due to physical obstruction of movement. FACTORS AFFECTING THE LENGTH OF TIME CRUDE PETROLEUM MAY BE RETAINED IN AN AREA lt has been assumed by sorne writers that oil is a relatively indestructible substance, and that accidental losses of oil may be cumulative in the bays, especially in the mud of the bottom. Gowanloch ( 1936) stated, "oil may come to rest in the substratum ( of bays) -where it may continue to produce whatever effects are the result of its interaction with sea waters." Smith (in Galtsoff et al., 1935) stated that, "the effect of oil pollution will last over a long period for the oil is carried to the bottom by suspended mud particles and released from time to time by storms, tonging, or dredging." Jensen (1950) evaporated a considerable number of crudes for about 5 hours at lOOºC and found that a loss of from 29 percent to 93 percent took place. He then "weathered" severa! crudes to determine whether or not they would evaporate at a slower rate under normal temperatures, and found that they lost from 39 to 43 percent by weight after exposure to air for four weeks. He believed that oíl when spread in a thin layer on water, and exposed to wind, would evaporate to the extent of 50 percent. Flushing of oils from the bays unquestionably removes much more oil. However, ·crude oil has a tendency to strand on mud flats at low tide, and wind may drive it .ashore in the marshes where it may stick on the mud. Part of it, as pointed out by Smith, may be carried to the bottom in deeper water by adhering to silt particles. Research Foundation personnel made a study of the fate of oíl thus carried to the bottom. BACTERIAL ÜXIDATION OF HYDROCARBONS ZoBell ( 1946) pointed out that certain bacteria may have a role in the formation of petroleum and also that others are hydrocarbon oxidizers and destroy crude oils in marine muds. ZoBell, Grant and Haas (1943) found a number of genera of bacteria and actinomycetes which attack and destroy various hydrocarbon compounds in pe­troleum, and demonstrated that they are widely distributed in marine muds. It became desirable to determine ( 1) whether or not such hydrocarbon-destroying microorganisms were present in muds of Louisiana bays and (2) if such microorganisms were present, at what rate Louisiana crudes and coinpounds of crudes were destroyed by them. ZoBell (1948, 1949) analyzed 108 samples of muds from Barataria Bay and sorne other locations for the presence of bacteria capable of oxidizing crude oil. The results are presented in Table 27, which is ZoBell's summary. TABLE 27 Summary of results obtained from examination of 108 mud samples from Barataria Bay region for presence and relative abundance of aerobic and anaerobic bacteria which oxidize minernl oíl. From ZoBell, '1949 Total number of samples 108 Percent Number showing aerobic oxidizers in 1 gm inocula Number showing aerobic oxidizers in 0.1 gram samples 101 80 93.6 74.0 Number showing aerobic oxidizers in 0.01 gram samples Number showing anaerobic oxidizers in 1.0 gram samples 39 78 36.2 72.3 Number showing anaerobic oxidizers in 0.1 gram samples Number showing anaerobic oxidizers in 0.01 gram samples 36 12 33.3 11.1 These samples were taken at various locations by J. F. Prokop of the Grand lsle Laboratory during 1947 and 1948 and were incubated at the Scripps lnstitution of Oceanography. Positive inocula of one gram of mud indicated the presence of at least one oxidizer per gram of mud, those of 0.1 gram indicated a mínimum of 10 oxidizers per gram of mud, and those samples positive with inocula of 0.01 gram indicated a mínimum of 100 oil oxidizers per gram of mud. Only 36.2 percent of the samples indi­cated that there were more than 100 oil oxidizers; ali of the remainder of the samples showed a relatively low concentration of oil oxidizers. Thus, while the microbes utilizing hydrocarbons were shown to be widely distributed (in fact, present virtually every­where), the relatively small numbers indicated that petroleum hydrocarbons in most of the muds were either small in amount or absent. ZoBell ( 1949) demonstrated that all crude oils tested ( five) from Louisiana were susceptible to oxidation by bacteria in muds from Louisiana bays, and that "bacteria] populations of the order of severa] billion cells per ml of medium developed in the presence of the crude oil." RATES OF ÜXIDATION OF LOUISIANA CRUDE ÜILS Prokop (1950) demonstrated the destruction of crude petroleum by severa] different methods. Brown (1950), Brown and Van Horn (1950) , and Brown, Van Horn, and Reid ( 1950) all demonstrated the destruction of crude petroleum and various compo­nents of crude petroleum by bacteria from Louisiana muds. Prokop (1950) and ZoBell (1949) measured the rate at which Louisiana crudes were decomposed by bacteria. Prokop measured the amount of oxygen consumed in oxidation of crude oil by a population of bacteria of 106 in a measured period of time. From these data he calculated the amount of methane destroyed. He chose methane because it requires a greater amount of oxygen than any other of the petroleum hydrocarbons and thus would give the most conservative figure. Table 28 taken from Prokop's report shows the amounts of crude petroleum which may be oxidized per given area, with different populations of bacteria. TABLE 28 Quantities of hydrocarbon oxidized per unit area of mud bottom for different periods of time, at 28ºC (Prokop 1950) Bacteria} population (millions per gram) Grams/acre/ day Barrei s/acre/ year Barrels/mile2/ year 1 10 100 1000 16.5 '165.0 1650.0 16500.0 0.044 0.44 4.4 44.0 '28.2 282.0 2820.0 28'200.0 ZoBell made similar calculations, arriving ata figure about one-half Prokop's, at 27ºC, or about 14,000 barreis per square mile with a bacteria! population of one billion per gram of mud. For citations of other similar studies the reports by Prokop and ZoBell should be consulted. Temperatures of 27ºC are summer water temperatures in Louisiana bays. Winter conditions would bring about a reduction of the rates of oxidation of crude oil. For lOºC of depression of temperature, the rate would be divided by about 2.3 and a further reduction of 10° would reduce the oxidation rate by 2.32• Temperatures of 7ºC are rare but l 7°C probably is close to mean winter conditions. SuMMARY OF DATA oN HYDROCARBONS The data presented in this section indicate that muds from the bottoms where oysters were produced were not generally polluted in the sense that there were detectable amounts of crude petroleum present. The amounts of extractable materials were shown to be generally low except at points where bleedwater was directly introduced into waters or where recent oil spillage was known to have occurred. In most cases these points were far removed from oyster-producing waters, but in sorne others they were in oyster pro­duction areas. In all cases the data showed that extractable "hydrocarbons" were rapidly diluted to a low leve!, and that the amounts actually found in the bays where oysters were produced were low in comparison with controls. In Barataria Bay specifically, "hydrocarbon" values were lower than elsewhere, although this is the area where most of the mortalities were claimed. It was indicated that the extractable materials in muds generally are of plant origin. This does not preclude the possibility that at any point there may not have been a small fraction of crude petroleum present, but it does show that in no case could the amounts be significant in effect on oysters. Comparisons of amounts of "hydrocarbons" in "high mortality" and "low mortality" arrns show that there was no significant difference. Taking into consideration the fact that petroleum hydrocarbons are thought to be evolved in such areas as the Louisiana marshes, and that in any inhabited area small additions of oíl from boats are unavoidable, it would have been surprising if the extrac­tions had shown no traces of hydrocarbons. Calculations based on the known production of bleedwater and the volumes of water in the bays show also that the amounts of actual petroleum hydrocarbons, if any were present, had to be extremely minute, and probably beyond detection by any method, away from the immediate vicinity of the discharge sites. These calculations confirmed and supplemented the data from chemical measurements. Studies on bacterial disintegration of crude oils and petroleum products showed that accumulation of petroleum hydrocarbons in the muds is not a possibility, taking into consideration the areas of the bays, volumes of water, and volumes of losses of crude petroleum. This does not apply to local areas at docks or in the immediate vicinity of bleedwater outlets where continuous large accretions occur. Nothing has been said about the use of visual, laste, and smell appraisals of pollution. However, to investigators in the field it was clear from the beginning that where oil pollution occurred, it could be seen, smelled, or tasted, and could be stirred from the bottom with a stick. With ten years of experience, it has been observed that only a small part of the total area has been affected by the occasional oíl losses which occur, and those affected have recovered quickly. In sorne large areas of high oyster mortality, notably lower Barataria Bay, not even so much as a slick has been observed. The "hydrocarbon program" yielded figures for the maximum concentrations of oil and bleedwater which might reasonably be expected to occur on or over Louisiana oyster beds. lt was then possible to set up experiments using amounts of bleedwater and crude oil in excess of those maximum figures. lf these amounts did not cause more oysters to die in the experimental than in the control groups, then it could logically be assumed that the maximum pollutio11 found in the bays did not cause mortality of oysters. Experimentation with Oil and Bleedwater Gowanloch (1936) stated: "It became an early surmise of the writer that crude oil itself was the important damaging agent. ..." He was referring to operations of the oil industry which he considered to be destructive to oysters. He had made certain field and laboratory studies which he believed showed that crude petroleum was highly toxic, at least to oysters. The field studies set up by Gowanloch consisted of known numbers of oysters placed in wooden trays on racks in areas which he considered to be polluted, and similar trays of oysters on racks in areas which he considered to be free of pollution. In the paper cited above he stated that there were six sets of these trays, of which two contained control oysters and four contained experimental oysters. According to Gowanloch the experimental oysters of one experiment had 46 percent mortality as against 9 percent in three months in controls. In his published paper he did not give locations of either control or experimental stations, or results of the other experiments. However, in testimony in the case of Doucet vs. The Texas Company, Gowanloch later gave further data concerning these field experiments. These data are assembled in Table 29. All of Gowanloch's trays and racks were soon riddled by shipworms. The wooden trays TABLE 29 Results of Gowanloch's field experiments testing the survival of oysters in areas "polluted with crude petroleum" and in "unpolluted" areas. June 15 to September '21, 1933 Experimental racks and conlrol racks Number of the rack 3 4 5 6 Within 10 ft. of BW outlet Near BW outlet Bedding ground of St. Pierre Bedding ground of Ludwig Bayou Beauregardt Mendicanl l. Bayou Beauregard, Mendicanl l. al Lake Barre al Lake Pello near Lake Doucet near Barataria Barataria LocaLion Oil Field Oil Field* Barre Field Pello Field Bay confrol Bay control Oysters per rack 100 100 100 100 50 50 Oysters recovered at end of study None 17 None 70 None 43 No. dead of those recovered None 32 4 Percent dead o.o 46 9 • "'Along side the bleedwater discharge ." and supports were not treated in any way. No provision was made for covers to prevent loss of oysters by wave action. The data in Table 29 show that Gowanloch completed two experiments, of which one showed mortality greater than that in the single control, while the other showed less than the control. Both of these experiments were in the Lake Pelto oil field where conchs (Thais) are numerous, while the control was in an ecological area where conchs are much less numerous. F·ailure to select more nearly equivalent areas for experimental and control stations was unfortunate. Forty-six percent mortality is not excessive m the area of the Doucet bedding ground in summer (see Tables 30 and 31). TABLE 30 Mortality of oysters kept in wire cages at various stations in Louisiana. Data are from Owen (1955) Mortality Mar. 22, 1949 to Oct. 18, 1949 Stalion percent Bayou Pierre, in Louisiana Marsh 56 Quarantine Bay, in seed area, east of Mississippi 4'2 Grand Bay, east of the Mississippi 47 Sandy Point Bay, near end of Mississippi River 48 Bayou Scofield, lower west Delta 58 Bay Adam, upper west Delta 61 Grande Ecaille, east of Greater Barataria Bay area 68 St. Mary's Point, upper Barataria Bay 40 Bassa Bassa Bay, middle Barataria Bay 35 Sugar House Bend, lower Barataria Bay 72 Lake Felicity, above Timbalier and Terrebonne Bays 40 Sister Lake, west ofTerrebonne Bay 29 Gowanloch (1936) also reported on a number of laboratory studies on the effect of crude petroleum, sludge, and bleedwater. These were conducted at the Grand Pass Laboratory of the Department of Wildlife and Fisheries. Gowanloch used glass-sided aquaria, 1 by 1 by 2 feet, which held about 30 liters of water. He used a running water system with a rate of flow of 500 ce per minute. In experiments on the effect of crude petroleum, Gowanloch passed sea water through a small amount (25 ce, originally) of oil confined on the water surface in an open-ended glass cylinder. The cylinder was held 'in a vertical position in one end of the aquarium. TABLE 31 Mortality r n~il olll;sh fnr identificaiion. On June 14, 1947, three baskets were placed ahout 3:) feel írom lhe hleedwater oullet, and six al a dislance of 1600 feet to the north-northeasl for controls. These latler were moved in Am::ust to a location 2600 feet norlheast. The experiment ran until April 20, 1949, ahout 22 months. Reíenmce: Menzel and Hopkins. 1953, Table 23, page 48. Distance irom BW oullet No. of Perce'lt íeel oyslers used deadt Experimental oysters 35 180 90 Control oysters 1600 to 2600 330 77 t After 11 months (midway of experimental period) the morlality was 26 percent in experimental oysters and 54 per cent in controle. Studies on Oyster Mortality TABLE 41D Study No . 4. Oysters of various sizes and origins, in Sea-Rae trays lined with half·inch mesh hardware cloth. were placed at four stations, two at or near bleedwater outlels and two (control localions) al 2100 and 2160 feet from the nearest bleedwater outlet (al the camp) and two to three miles from tbe other outlet (in Crooked Bayou) . One of the controls wa& in Bay Coon Road, to tbe norlheast of Bay Ste. Elaine camp (Fig. 31), and the other to the southeast. Experimental trays were placed at various levels, and at varíous distances from the bleedwater outlets, up lo 200 feet away. Because no significant differences in mortality rales were recorded for different levels and distances of tbe experimental trays, all levels and distances are averaged in the table below. The experiment lasted from August, 1947 lo January, 1948. Reference: Menzel and Hopk.ins, 1953, Table 35, page 67. Distance from No. Percent Locations BW outlel (feet) oysters used dead Experimental oysters At Ste. Elaine camp 35 to 100 2609 24 At Crooked Bayou tank battery 100 to 200 602 22 Control oysters 207 º from BW at Ste. Elaine 2100 400 22 340º from BW at Ste. Elaine 2160 1590 20 TABLE 4lE Study No. 5. Oysters from 70 to 100 mm long were placed in 4 Sea-Rae trays, 300 oyslers to a Lray. Two of these lrays were placed 100 feel from the bleedwaler outlet al the Ste. Elaine L. L. and E. tank battery and the other two were placed 2160 feet to the norlh-northwest. The experiment was set up on January 11, 1948 and continued until February 7, 1949. Reference: Menzel and Hopkins, 1953, Table 60, page 96. Distance from No. of Percent BW outlel (feel) oysters used dead Experimental oysters 100 600 62 Control oysters 2160 600 47 TABLE 41F Study No. 6. Oysters about 11 months old were placed in 12 hardware cloth baskcts, SO oyslers in each. Four experimental baskets were placed al two levels 25 feel from the bleedwater outlet al the Bay Ste. Elaine L. L. and E. lank battery. Two sets o( <.ontrols, one examined monthly and the other examined lwice in one year, were placed al a distance of 2160 feet to the north­northwesl. Each control group consisted o( 200 oysters in four baskets. The experimenl was begun April 23, 1948, and lerrninated April 20, 1949, but so many oysters were spilled and Jost after October that data are presented here only to October 20, 1948. Reference: Menzel and Hopkins, 1953, Tables 63-66, pages 101-103. Dislance from No. of Percenl BW outlet (feel) oysters used dead Oct. 20, 194a Experimental 25 200 31 Control group 1 2160 200 26±3 Control group 2 2160 200 52±1 TABLE 41G Study No. 7. Spat up to 5 months old attached lo galvanized tin plates were placed in trays. One tray was placed near the botlom 25 feet south of the L. L. and E. bleedwater outlet al the Ste. Elaine carnp, and two trays (controls) were placed al a dislance of 350 feel to the north. The study began on Novemher 28, 1948. Menzel and Hopkins give data to May 9, 1950 on the experimental oysters, but the controls were lost by accident, one November 2, 1949. and one August 20, 1949. Since the three lrays had comparable data lo August 20, the mortalily data on that date are presenled in the table. Reference: Menzel and Hopk;ns, 1953, Tables 74--76, pages 115-117. Dislance Írom No. of Percent BW outlet (feet) oysters used de ad Experimental oysters 25 ft s 60 35 Control group l 350 ft N 48 50 Control group 2 350 ft N 57 44 TABLE 41H Study No. 8. Oyslers about 14 months old were placed in four Sea-Rae trays, 175 to each. Two experimental trays were placed on racks within aboul 25 fecl of the bleedwater outlets al the Ste. Elaine L. L. and E. tank hallery; the two conlrols were placed on racks at a distance of 2160 feet north~northwest . The study began September 18, 1948, and was terminated on April 25, 1949. Reference : Meozel and Hopkins, 1953, Table 108, page 145. Distance from No. of Percent BW outlel (feel) oyslers used dead Experimental trays 25 350 35 Control trays 2160 350 27 EXPERIMENTS TO TEST THE EFFECT ON ÜYSTERS OF BLEEDWATER PRODUCED IN THE LAKE BARRE ÜIL FIELD The Lake Barre oil field of the Texas Company lies in the southern part of the "lake" (see map, Fig. 27). The water in the "lake" has salinity ranging from around 18 to 26 ppt. Around the Lake Barre oil field oysters grow prolifically in the intertidal zones, on pilings and bulkheads and in small reefs on the mud. Subtidal oysters also grow in sorne areas near the camp, attached to bulkheads. lntertidal oysters are mostly less than eighteen months old. The field produced about 4000 to 9000 barreis of bleedwater daily, averaging about 6600 per day, from June 1, 1947, to June 1, 1949, the period of bleedwater studies. Thus this field produced the largest amount of bleedwater of any oil field located in oyster-producing waters, and experimentation was more extensive here for that reason. AH of the bleedwater is emptied into the water through two "gun barreis" set about 20 feet apart. The experimentation was around these outlets (Figs. 33 and 34) . See Table 42. TABLE 42 Studies at Lake Barre Oíl Field testing the effect of bleedwater on survival of oysters (Menzel and Hopkins, 1951) TABLE 42A Study No. l. This &tudy was designed to check on the settiog and the survival of spat al various distances lo the south from the bleedwater oullets and al a control station. Shell baga were placed in the water al two levels and al varying distances on May I, 1948. and werc taken up at intervale oí aboul two months. New shell bags were set in the water when the old ones were taken up Cor examination. The study was concluded on November IS, 1948. Reference : Menzel and Hopkins, 1951, Tables 4 aod 5, pages 16-17. Dislance from No. oyslers Percenl Dates BW outlets (feet) setling per shell de ad Shell bags 2 feet a hove bottom: May 1, l!i48 to July 4, 1948 July '2, 1948 to Sept. 15, 1948 Sept. 5, 1948 to Sept. 15, 1948 Shell bags on bottom: May 1, 1948 to July 5, 1948 July 2, 1948 to Sept. 5, 1948 Sept. 5, 1948 to Nov. 15, 1948 50 43 12 85 27 16 150 35 14 250 42 21 2000 (Con trol) 28 35 50 9 19 85 n 17 250 13 11 2000 (Control) 20 18 50 2 10 85 1 41 150 3 28 2000 (Control) 1 22 50 23 28 85 30 22 150 26 17 250 47 51 2000 (Control) 22 35 50 1 20 85 9 17 150 14 13 250 11 23 2000 (Control) 15 19 50 16 20 85 11 32 150 13 19 250 13 19 2000 (Control) 6 85 F1G. 33. Aerial photo of the Lake Barre oil field. The point where the bleedwater outlets are located is indicated. F1G. 34. The two bleedwater outlets at the Lake Barre oil field. Largest production of bleedwater in the south Louisiana area is here. TABLE 42B Study No. 2. This study was sel up to measure the survival of 2-monlhs-old oysters dose to the bleedwater outlels and al a dislance of more than 1h milc. Oyslers were placed in hardware doth baskels which were suspended al varying levels above the bottom. They were placed in lhe water on June 14, 1947. On July 3, 1947 additional young oysters attached to shells were strung on wires in the baskets in such manner thal they would not touch the bottom. On Ju)y 27, 1947 these young oyslers were checked for mortality, as they were again on January 22, 1948. Reference : Menzel and Hopkins, 1953, Table 12, page 26. Dislance from Feet ahove No . of Percent Dates BW outlets (feet) botlom oyslers dead July 3, to July 27 80 3 59 24 1.5 60 12 o 55 9 3200 3 60 15 1.5 60 2 o 55 13 J uly 27, 1947 to Jan. 22, 1948 80 3 22 9 1.5 24 4 o 24 13 3200 3 26 4 1.5 39 13 o 27 7 TABLE 42C Study No. 3. Ten-monlh·old oysters were used in an experiment further testiog the effecL of Lake Barre bleedwaler. Fifty of these young oysters were placed in each of 12 hardware cloth baskets. On April 12, 1948, four of these baskets (experimental) were placed in the water et a distance o[ 100 feet west of the bleedwater outlets and eight were placed al a control station 2000 feet lo the north-northeast. The experimenl was terrninated on April 21, 1949, a year later. Note that one experimental basket was lost. Reference: Menzel and Hopkins, 1951, Table 14, page 30. Dístance and direction Level above No . of Percent dead Dates from BW oullet hottom (inches} oysters used in one year April 12, 1948 to April 21, 1949 100 ft. w 18 50 85 4 100 71 2000ftNNE 18 200 74 4 200 67 TABLE 42D Study No. 4. Two hundred oysters approximately 2 months old wcre p)aced in each of 15 Sea-Rae trays which were lined with half-inch hardware cloth. On July 16, 1948 these trays were suspended around the bleedwater outlets at various levels, distances, and directions, and at the control station 3500 feet to the south. Since there seemed lo be no difference in the two levels used, the different levels al a station are averaged. This study was marred by excessive losses of oyslers from sorne trays with consequent large possibilities for error in the mortality percentage. AH trays with such excessivc loss were eliminated from this summary. For the full da,ta see the original I"eporl (Menzel and Hopkins, 1951), Table 23, page 41. Duration of the study: July 16, 1948 to May 18, 1949. Distance and direction No. of Percenl from BW outlet (feet) oyslers used dead 25ft N 392 71 75 ft N 190 7 100 ft s 205 6 150 ft N 204 13 150 ftS 408 14 3200 ft S (Control) 410 20 TABLE 42E Study No. 5. Oysters of various size classes were placed in Sea~Rac lrays on wooden frames at 10 locations in and around the Lake Barre field, as shown in the table below. Sorne trays were placed near the surface and sorne near Lhe bottom. There were lwo control locations, al 3200 feel and 4200 feet. There were excessive losses of trays and oysters due to storm damage. Tbe table presents mean mortality of all size c1asses for those oysters placed close lo the bottom only, sioce nol enougb was left of the experimental oysters close to the surface to give sigoificanl figures. For the details of both bottom and surface trays see Menzel and Hopkins (1951), Table 32, page 58. The study hegan August, 1947 and ended in August, 1948. Direction and distance No. of Percenl dead from BW outlet (feel) oysters used in one year 40ft sw 225 99• 80 ft w 710 67 140 ft s 208 48 180 ft w 202 57 240 ft s 206 67 280 ft w 208 62 340 ft s 201 65 500ftWSW 300 59 3200 ft S (Control) 920 65 4200 ft SE (Control) 300 60 *The original tray of 225 oysters 40 feet southwest of the outlet had 98 percent mortality between Augusl 7 and Scptemher 21, 1947. It was replaced by another tray, which also had excessively bigh mortalily. Calculated total mortalily was 99.S percent. TABLE 42F Study No. 6. Setting and survival of spal on oysters placed in trays al various distances and directions from the Lake Barre hleedwaler outlets in the late summer and fall of 1947 (See Study No. 5) . These were counted and checked Ior total mortality in August, 1948. Reference: Menzel and Hopkins, 1951, Table 44, page 71. Distance and direc.tion No. of Mean spal Percenl Irom BW oullet (feel} lr.ays per lray mortalily 80 ft w 4 102 5 140 ft s 1 500 5 l80ft w 1 193 14 240 ft s 2 170 12 280 ft w 2 401 7 340 ft s 1 190 18 3200 ft S (Control) 5 57 16 4200 ft SE (Control) 1 111 '14 TABLE 42G Study No. 7. Trays of oysters were placed al the bleedwater outlets and al varying distances, directions and levcls from the discharge. These oyslers were variable in age and size and were random-selected. The study began on October l, 1947 and ended February 5, 1948. Reference: Menzel and Hopkins, 1951, Table 46, page 81. Distance and direclion Distance above No. of Percenl from BW outlet (feet) boUom (feet) oysters used mortality Between outlets 3 94 23 1.5 111 95 o % 100 20 ft N 3 67 15 1.5 100 8 o 109 14 30ft w 3 66 21 1.5 78 24 o 34 65 40ft N 3 119 '14 1.5 104 11 o 104 62 40 ft w 3 69 9 1.5 75 37 o 75 37 60 ft N 3 105 20 1.5 106 8 o 105 61 60ft w 3 65 12 1.5 so 14 o 50 28 Studies on Oyster Mortality TABLE 42H Study No. 8. About one hundred oysters were placed in each of 42 Sea-Rae trays lined with half-inch mesh hardware cloLh. These trays of oysters were placed in various positions around the bleedwater outlet as shown below on April 12, 1948 and taken up April 24, 1949. Oyslers were probably about 18 months old on the average, al the initiation of the study. Reference: Menzel and Hopk.ins, 1951, Table SO, page 87. Dislance and direction No. of Percent from BW outlel (feel) Level oyslers used mortality 20ftW Top 199 97 Bottorn 199 99 35 ftSW Top 199 <}4 Bottorn 197 100 40 ft w Top 199 98 Bottorn 200 99 50 ft w Top 201 94 Bottorn 200 93 60 ft s Bottorn 200 90 70 ft w Bottorn 200 90 75 ft s Bottorn '200 93 100 ft w Top 202 88 Bottorn 202 83 115 ft s Top 201 79 130ft w Bottorn 199 93 lSOftW Top 196 77 Bottorn 202 73 170 ft w Bottorn 198 58 180 ft w Top 200 70 Bottorn 200 90 TABLE 421 Study No. 9. Fifteen-month-old oysters were placed in lined Sea-Rae trays. There were 175 oysters per tray. Trays were placed in relation to bleedwater outlets as shown below. The study began Octoher 15, 1947 and terminated May 15, 1949 {7 months laler). Reference : Menzel and Hopkins9 1951, Table 54, page 94. Distance and directíon No. of Percenl from BW outlet (feet) Level oysters used rnortalíty 25 ft N Top 169 60 Bottorn 175 91 25 ft sw Top 173 94 Bottorn 176 100 so ft s Top 172 37 Bottorn 176 87 75 ft N Bottorn 174 21 75 ft s Bottorn 175 27 100 ft s Bottorn 175 26 150 ft N Top 172 26 Bottorn 174 28 3200 ft S (Control) Top 175 18 Bottorn 172 17 At Bayou Bas Bleu, 5 miles N (Control} t Top 163 52 Bottorn 169 SS t Reference: Menzel, 1950c, Table 20, pages 28-29 . SUMMARY OF THE BLEEDWATER STUDIES AT LAKE BARRE As a means of summarizing the data on the studies of the effect of bleedwater on oysters at Lake Barre, Table 43, modified from Table 62 in the report by Menzel and Hopkins (1951), is presented. In order to make mortalities comparable, ali are reduced to percent per day, and the distances from the BW outlets are combined into segments. Directions are ignored. TABLE 43 Summary of mortality rates in bleedwater experiments at Lake Barre Oil Field Range of mortality, per day Distance from BW oullet (leel} Top trays Bottom Lrays O to 25 0.18 to 0.25 0.25 to 1.47 35 to 50 0.11to0.19 0.27 to 0.49 60 to 75 0.10 to 0.16 0.17 to 0.20 80 to 115 0.20 to 0.21 0.13 to 0.20 140 to 180 0.08 to0.24 0.09 to 0.19 240 to 500 0.16 to 0.18 0.17 to 0.19 2000 to 4200 0.10 to 0.20 0.11to0.18 EXPERIMENTS TESTING THE EFFECT OF BLEEDWATER EFFLUENTS OF THE CAILLOU ISLAND ÜIL FIELD ON ÜYSTERS The Caillou Island oil field is located in the lower part of Terrebonne Bay in a wide expanse of comparatively deep water (maps, Figs 21 and 30), near the large pass into the Gulf. The salinity is high (22 ppt to 30 ppt) in this area. There were three bleed­water outlets, one of which was used in most of the experiments. Production of bleedwater from June 1, 1947 to June 1, 1949, during which period the experiments described below were carried out, was about 2000 to 14,000 barreis daily and averaged about 5000 barreis a day. More than half of this was discharged at the site where nearly all experiments were conducted. F1G. 35. Aerial photograph showing the Caillou Island oil field. Locations of bleedwater outlets and experimental areas are indicated by arrows. Fig. 35 shows the general layout of the field, and the expanse of water around it. Oysters grow attached to pilings in the camp, and intertidal reefs are found in coves and bayous of the barrier island to the south. However, no subtidal oysters grow on the bottom and the area long since ceased to be productive of commercial oysters because of the exposed location. Set of spat is good, but unless protected from predators few of these survive for more than a few weeks. Data on experiments carried out in this field are contained in Table 44. TABLE 44 Studies on the efiect of bleedwater on survival of oysters at Caillou Island Oil Field TABLE 44A Study No. l. Three trays of experimental oysters were placed 35 feel from the bleedwater outlet, with 100 oysters in each tray. The oysters were f'rom the Lake Barre oil field. Three trays of control oyslers, with 200 to 250 oysters in each tray, were placed 4900 feet from the hleedwater outlet. The control oyslers were from Bay Ste. Elaine and were slightly larger than the experimental ones. Reference: Menzel, 1950a, Table 1, pages 5--6. No. of Level Percent Dates oysters of lray* mortality Oct. 6, 1947 to Experimental 100 Top 71 Sept. 30, 1948 100 Middle 60 Control 250 Top 75 200 Bottom 73 • The experimental hollom lray and the control middle tray were losl early in the experimeot. The experimental middle tray was lost during lhe lasl month of the experimental period. TABLE 44B Study No. 2. Oyslers, in trays containing about 100 each, were placed around a bleedwater outlet al eighl points of the compass and exactly 100 feet from the effiuenl opening. These were compared wilh lwo trays 4-00 feet to the east and two lnys 4500 feel lo the west. These also held about 100 oysters each. Ali lrays were aboul 3 feet above lhe bottom in aboul 8 feel of water. Th6 experimenl began Ocloher 17. 1948 and ended April 1, 1949. (The 6rsl half of lbe original experimenl, April 4 lo October 17, is not reporled here hecause there were no controls until two monlhs after the heginning of tbe study.) Reference: Menzel, 1950a, Table 3, page 11. Dislance from No. o! Percenl BW outlet (leet) oysters dead 100 ftN 96 19 lOOft NE 99 19 100 ft E 100 13 100 ft SE 100 14 100 ft s 100 16 100 ft'SW 100 23 lOOft W 100 17 '100 ft NW 99 14 400 ft E 187 15t 4500ft w 200 10 t There was a possible error of 6% in this lray due lo loss of 11 oysters. TABLE 44C Study No. 3. An experiment on the selling and survival of spat on lrays of oyslers near a bleedwaler oullet and al a distance. This used trays of oysters in a ring al 16 poinls of lhe compass and 100 Ieet distance from the centrally placed bleedwater outlet. Conlrols were four lrays al 400 feet and four trays al 4500 feet. Depth level was tbe same everywhere (3 feet above bottom) . Period was March 28 (Ior experimental trays) and May 26 (for controls) to October 17, 1948. The time difference was nol significanl since sel did nol occur until May. Reference: Menzel, 1950a, Table 10, page 18. 16 exp. lrays-100 fl 4 conl. trays-400 ft 4 conl. trays-4500 ft Period Spal per lray P ercent dead Spat per lray Percent dead Spat per tray Pereent dead March 28, 1948 to Oct.17, 1948 403 4.0 1450 5.6 3.7 TABLE 44D Study No. 4. Dates : September 19, 1948 to April 26, 1949. Three trays with 175 oysters eacb were placed 100 feet from hleedwater outlets, ooe north, one northeast and ooe south . One control tray was placed 4500 feel wesl of the bleedwater outlet. Oysters were 10 to 16 months old and selccled for uniform size. Reference: Menzel, 1950a, Table 12, page 21. Distance and direction from No. of Percent BW o u ti el ( fee l) oyslers dead 100 ft N 175 16 100 ft NE 175 13 100 ft s 175 30 4500 ft W (Control) 176 35 TABLE 44E Study No. S. Dates : May 2, 1948 to Novemher 15, 1948. A check on seuing and survival of spat 100 feet and 4500 feet from the bleedwater outlet, Chicken wire bags filled witb shells were pul in place al the two locations on May 2, and at íntervals these hags were taken up and replaced by new ones. Set of oysters and mortality was determined by systematic random sampling: of 25 to 30 shells from each bag al the end oí each time interval. Bags were placed al two levels; on the bollom and three feel above bottom. Results are reported as average set per sbell and percenl dead per shell. Reference : Menzel, l950a, Table 18, page 27. Distance from BW outlet (feet) Level above hollom Total spat per shell Percent de ad '100 ft from BW 4500 ft from BW 3 ft. oft. 3 ft. oft. 15.2 7.0 13.9 6.2 11 10 11 11 TABLE 44F Study No . 6. July 31, 1948 to May 15, 1949. Young oysters two or tbree months old, ali with exactly the same bistory, were used lo test the effecl o[ bleedwater. Four trays each contaioing 200 o[ these youog oysters were used. Three of these were placed 100 feet north, 100 Íeet northeast and 100 feet south of the bleedwaler outlets; the fourth was placed 4500 feet to the west. Reference: Menzel, 1950a, Table 22, page 35. Dislance and direclion from No. o[ Percent BW outlel (feet) oysters dead 100 ft N 201 '23 100 ft NE 200 16 100 ft s 200 30 4500 ft W (Control) 200 20 EXPERIMENTATION ON THE EFFECT OF BLEEDWATER ON ÜYSTERS AT THE Doc LAKE ÜIL FrnLD The Dog Lake oil fi.eld líes in a maze of small "lakes" and bayous to the southeast of Caillou Lake (Sister Lake) , and to the northwest of Lake Pelto (Fig. 21). Bleedwater is discharged at two locations, roughly a little more than a mile each from the camp, one to the southwest, and one west. The westerly outlet was used in a single study, and controls were placed at the camp. Fig. 36 shows the locations of the bleedwater outlets and oyster reefs. Oysters grow naturally in this fi.eld and all around it. They are par­ticularly abundant around the camp, and are regularly harvested by the oil fi.eld workers. Data on experimentation are contained in Table 45. F1G. 36,A,B. The Dog Lake field camp (36A) and the Dog Lake tank battery, where the bleed­water outlet is located ( 36B). Experimental oysters were placed at the bleedwater outlet; the con­trols at the camp, 6,450 feet away. Studies on Oyster Mortality TABLE 45 Test of the effect of bleedwater on survival of oysters at Dog Lake Oil Field Study No. l. Three trays of oysteu were placed near the two bleedwater outlels under Unit 12 tank battery, and three control lrays al the camp, 6450 feet easl of Uníl 12 lank hallery and 5600 feel from the closesl of the three tank batleries. At eacb location one tray was on bottom, one 18 inches above, and one 36 inches ahove bottom and a few inches above low tide level. Experimental oyslers were from Lake Barre and control oysters from Bay Ste. Elaine. The experiment began October 15, 1947 and contioued to October 24, 1948, but two of the control trays were lost before January and the third disappeared before October, 1948, so data are presented only for the periods October 15 to Novernber 16, 1947, and October IS, 1947 to Jaouary 17, 1948. Mortality figures are for tbe trays remaining al tbe end of the period. Reference: Menzel. 1950c, Table 1, page S. Mortality, percenl No. ol Localion of trays oysters il-16-47 1-27-48 Tank battery (experimental) 360 3 4 Camp (control) 400 8 18 EXPERIMENTATION ON THE EFFECT OF BLEEDWATER ON ÜYSTERS AT THE LAKE PELTO ÜIL FIELD "Lake" Pelto is a highly saline open-water hay lying to the southwest of Terrebonne Bay and separated from the Gulf of Mexico by a narrow barrier island. There are wide open and deep passes at both ends of the barrier island (Map, Fig. 21). The Lake Pelto oil field of The Texas Company lies near the eastern end of the hay, above Wine Island Pass. This field produced an average of 1385 barreis of bleedwater daily in the period from June 1, 1947, to June 1, 1949, the period of the experimentation with bleedwater. This amount was discharged into the open water of the hay from four closely clustered outlets (Fig. 37). Sorne of the best oysters seen in Louisiana grew attached to timbers in the Lake Pelto oil camp. These were in shaded and sheltered positions. No oysters grow naturally on the bottom below low tide level in Lake Pelto. At certain points there are prolific beds of intertidal coon oysters along the shores of the hay. Only one study was made testing the effect of bleedwater in the Lake Pelto field (Table 46). TABLE 46 Study testing the effect of bleedwater on survival of oysters at Lake Pelto Oil Field. Menzel, 1950b Tbree lrays of oyslers of assorled sizes were placed near the four bleedwater discharge siles oo October 3, 1947. The nearest discharge site wa& 35 feet away and another was 125 feet distanl on the opposite side. Mortality in these trays was compared with rates in oysters al various dislanl points in the Louisiana oyster-producing area. The study was terminated on November 29, 1948. Because other studies did not run for comparable periods, the mortality rales are reduced lo percenl per day Cor all control stations and the experimental station. The cumulative mortality for the 423-day period was 84 percent (79 percent in the bollom lray and 92 percenl in the upper lrays). Morlalily per day Reference Localily percenl Menzel, 1950d, page 18 Bayou Bas Bleu (Exp. 1) 0.17 Menzel, 1950d, page 18 Menzel, 1950a, pages 5--6 Menzel, 195-0a, pages 5--6 Menzel, 1950b, Table 2 Bayou Bas Bleu ( Exp. 1) Caillou l. Camp (Exp. 1) Caillou l. Camp (Exp. I) Lake Pelto ( 4 ft above bottom) 0.19 0.21 0.20 0.22 Menzel, 1950b, Table 2 Lake Pelto (few inches from bottom) 0.19· GROWTH OF ÜYSTERS SuBJECTED TO CRUDE PETROLEUM In order to determine whether or not oysters in contact with crude petroleum grow normally, four field studies were carried out at Bassa Bassa Bay in conjunction with survival studies. The data are summarized in Table 47. TABLE 47 Shell growth of oysters sprayed with oil TABLE 47A Study No. l. Oyslers were sprayed with crude pelroleum weekly for six months, August 9, 1947, to February 9, 1948. The growth íncremenl of oil-sprayed oysters was compared with that of unlreated oysters. There were two groups, one of about 3 lo 4-year-old oyslers from Bassa Bassa Bay and another of aboul 2-year-old oysters from Barataria Bay near Saturday lsland. Tbe experimental and control oysters were kepl in trays at the Bassa Bassa station. Reference: Mackin, l948a, Table S, page 8. No. ol Origin lncrease in Treatmenl oysters used of oysters lenglh (mm) Experiment 169 Bassa Bassa 8.85 Control 381 Bassa Bassa 11.8 Experiment 228 Saturday lsland 11.0 Control 453 Saturday lsland 9.0 TABLE 47B Sludy No. 2. The second sludy was a duplicate of the firsl. The period was October 8, 1947 lo March 31, 1948, or about six months. The oysters were ali about standard seed size (for Louísiana planting), and were from a natural reef in the Lake Barre oil field. Experimental oysters were sprayed wilh crude pelroleum al inlervals of about one week for the 6-month period. Reference: Mackin 1948b, Table 3, page 4. No . of oyslers lncrease in measured lenglh (mm) Experiment (sprayed with oil) 356 10.7 Control (unsprayed) 640 10.5 TABLE 47C Study No. 3. Experimental trays of very young spal were &prayed wjth crude petroleum for a six·monlh period al weekly i~tervals. Spat were from tbree lo four months old al beginning of the sludy on August 9, 1957 and nine to len montbs old at lime of measurement. Reference: Mackin, 1948a, Table 7, page 10. No. ol No. of No. per Final trays young oysters tray leogtb (mm) Experiment 4 269 67 53.2 Control 8 541 68 51.8 TABLE 47D Study No. 4. Average size altained by oyslers atlaching and growing in trays sprayed with crude petroleum al one-week intervals, was compared with unsprayed controls. These young oysters were atlached lo the trays themselves. Since the trays were placed in the water on August 21, 1947, the oldest of the young oysters al the end of the litudy on March 31, 1948, were ahout seven montbs old, and the youngesl were about .6ve montho old. Reference : Mackin, 1948a, Table 5, pag:e S. No. of No. of Spat Final trays oysters altacbing per lray leogtb (mm) Experiment (sprayed weekly) '2 165 82 36.4 Controls (unsprayed) 4 273 68 36.6 GROWTH OF ÜYSTERS NEAR BLEEDWATER DrscHARGE SrTES A number of studies made by Menzel and Hopkins in oil fields of Terrebonne Parish were designed to determine whether or not bleedwater could produce stunting of oysters, and if so, at what distances from sources the effect was found. Most of these were carried out in conjunction with the survival studies at the same stations. The data from each oil field are made the subject of a table in which all results of all growth studies at that field are summarized (Tables 48, 49, and 50). TABLL 48 Growth of oysters exposed to bleedwater at the Bay Ste. Elaine Oíl Field TABLE 48A Study No. l. Sbell bags were suspended ~n the water 25 feet from the hleedwater outlets, and Lhe growth of the spat which allached lo the shells was compared with growth of spal which atlached to shells in a control bag al a distance of 350 feet. Bags were placed in the water al varying times and ali were taken up on Decemher 2 or 4, 1948. Refereoce: Menzel and Hopkios, 1953, Table 20, page 42. Average size of spal on December 2-4, 1948 (mm) Date placed in water Position in relation to bottom Experimenl 25 fl from BW outlet Conlrols 350 ll from BW 4-30---48 7-2-48 7-2-48 9-2-48 9-2-48 on bottom 1 ft above bottom on bottom 1 ft above bottom on bottom 16.4 by 13.4 23.5by17.9 16.8 by 14.2 12.8by11.0 16.7 by 13.8 26.8 by 20.4 29.1 by23.4 27.7 by 22.l 14.9 by 13.2 15.7by13.8 TABLE 48B Study No. 2. Young oyslers less than 37 days old were placed in wire baskets and measured al irregular intervah for a seven·month period, from June 14, 1947, to January 15, 1948. Two lrays were placed 35 feet from each of Lhe bleedwaler outlelS al Bay Ste. Elaine lank battery. The conlrols were firsl kepl at a distance of 1600 feel, later changed to 2160 Íttl. Reference : Menzel and Hopkins, 1953, Tables 24 to 26, pages 45 lo SO. No. of oysters Size on Size on measured on 6-14-47 (mm) 1-15-48 (mm) 1-15-48 Experiment (35 ft from BW) 12.8by10.9 72 by 54 59 1600 ft and 2160 ft from BW (Control) 12.1by11.0 54by42 '148 Studies on Oyster Mortality 109. TABLE 48C Study No. 3. Shell growlh and productivily (yield in sacks per sack planted) of oysters at four slations, varying from 25 to 200 feel from hleedwater oullets al the Bay Ste. Elaine L. L. and E. and Crooked Bayou tank batteries, were compared with growth and productivity of conlrols at two locations, 2100 and 2160 feet from the nearesl bleedwater discharge. The experimenl ran from August, 1947, to August, 1948. Reference : Menzel and Hopkins, 1953, Tables 30, 49, 51, aild 59. Experimental Control locations locations Number of oysters used 3411 4884 Percent increase in length* 37.8 34.4 Percent increase in width* 34.3 30.4 Percent increase in length X width* 86.5 74.3 Yield, sacks per sack plantedt 0.88 0.89 í* Average of percenlage increases of 19 lots of graded sizes al control locations and 32 lots of graded sizes at experimental locations. t Average of yields per sack planted calculated for 20 lots of graded sizes al control locations and 31 lots of graded sizes al experimental locations. TABLE 48D Study No. 4. Four wire baskets, each containing SO oysters 10 lo 11 months old, were placed within 25 feet of the hleedwater discharge al the L. L. and E. tank battery al Bay Ste. Elaine on April 23, 1948. The control location, 2160 feet lo the notthwesl, also had four baskets with 50 oyslers eacb. Controls and experimental oysters were measured al the beginning of the study and again on April 20, 1949, aboul one year later. Percent increase in average dimensions and yield in ºsacks hanested per sack planted'' are shown below. Reference: Menzel and Hopkins (1953), Tables 67, 73, pages 103, 107. Percenl increase, Mean Yi.eld, sacks Lenglh Width Thickness per sack planted 25 ft from BW discharge 60.3 48.0 70.3 3.0 2160 ft from BW discharge 43.5 33.3 76.3 2.4 TABLE 48E Study No. S. Four trays each contained 175 oysters, aboul 15 months old and ranging in size from 52.S to 67.S mm. Two trays (experimental), were placed between the two bleedwater outlets (25 feet from nearest) al the Bay Ste. Elaine L. L. and E . tank hattery. The two conlrols were placed 2160 feet to the northwesl. The study began September 18, 1948, and ended on April 25, 1949, ahout seven months laler. Oysters were rneasured al the heginning and al the end of the study. Yields were computed from growth and rnortality data. Reference: Menzel and Hopkins (1953), Tables 113 and 114, pages 148 and 149. Percenl Increase in 7 monlhs Yield, sacks Length Width Thickness per sack planted 25 ft from BW discharge 38 49 36 1.64 2160 ft from BW discharge 26 33 33 1.52 TABLE 48F Study No. 6. Bollom plantings were made al two places; one of 1.5 acres was jusl offshore from the Bay Ste. Elaine L . L. aod E. and State tank battery where bleedwaler is discharged, lhc other (control) was in a cut canal approximately one mile west of the Bay Ste. Elaine Camp and comprised 1.4 acres. Natural oysters grew in the latter location, which had a strong scour currenl and hard hollom. The experimental plot was ahout average for Louisiana plantings, with a fairly stiff mud bottom. Both areas had heavy boat traffic. Approximately 600 sacks of seed were planted on each plot, ali from the sarne seed source, in the period October 18-31, l94i. Samples of aboul lhree sacks for each plot, one each taken from different boatloads and different parts of each boatload, were measured al lime of planting. Samples were taken moothly until January 18, 1949, aboul 14 months after planling. The oysters in these samples were measured and meaos computed. Data are presented here comparing the first and last samples frorn each plot, to show growth in length and width. Reference: Menzel and Hopkins, 1952, Tables 91, 98, and 99, pages 121, 132, and 133. Length, mm Width, mm Yield, Jan. 1949, sacks Localion of plot Oct. 1947 Jan. 1949 Oct. 1947 Jan. 1949 per sack planted* At tank battery (exper. plot) 65.3 96.7 39.6 65.5 0.3 to 0.5 One mil e W (control) 67.5 89.6 39.3 56.3 0.8 to 1.2 *The maxirnum yield obtainable was 1.0 to 1.1 on the experimental plot and 1.1 to 1.3 on the control plot in March and April, 1948. Studies on Oyster Mortality TABLE 49 Growth of oysters exposed to bleedwater at Lake Barre Oil Field TABLE 49A Study No. l. Wire bags of shells were suspended two feel above the bottom al various dililances from the bleedwater outlets. Control bags of sbells were placed 2000 feel to the norlh~nortbeast. Spal which altached to these sbells wue measured on November 16, 1948. Only the measuremenls of the largesl 25 percent of the spat are recorded bere. These measuremenls represenl approximalely two months of growtb in 1948. Reference : Menzel and Hopkíos, 1951, Table 10, page 23. Dislance from BW outlets (feet) No. of spat measured Mean size (mm) of largesl 25% Length Width 50 ft s 85 ft s 256 272 26.2 26.6 20.7 20.6 150ftS 250 ft s 162 20'1 29.0 26.9 22.6 20.7 2000 ft NNE 227 26.8 21.9 TABLE 49B Study No. 2. The second study of growtb of oyslers exposed to hleedwater al Lake Barre was identical to Study No. 1 e.xecpt that shell bags were on the bottom instead of two feet ahove. Reference : Menzel and Hopk.ins, 1951, Table 11, pages 24. Mean 1ize (mm) of large&t 25% Dislance from BW outlets (leet) No. of spal mea&ured Lengtb Wid1b 50 ft s 157 13.7 11.5 85 ft s 210 15.8 13.2 150 ft s 266 17.0 13.7 250 ft s '292 19.8 16.9 2000 ft NNE 222 26.0 20.5 T ABLE 49C Sludy No. 3. Three baskets of young oyslers less than one year old were placed 80 feel from the bleedwaler discharge al the Lake Barre oíl field. Three controls were placed 3200 ft S of tbe bleedwater discharge. The three experimental basket& held a total of 159 oysters; the three control basket& held 144 oyslers. The experiment hegan on July 27, 1947. when the young oyslers were measured for length and width. The study was lerminaled January 22, 1948, after a period of approximately 6 months. Mortality reduced the measured groups lo 84 and 64 oysters respectively. Reference: Menzel and Hopkins, 1951, Table 12, page 26. Mean size (mm) Mean size (mm) July 27, 1947 Jan. 22, 1948 Length Widtb Lengtb 80 ft from BW discharge 27.8 23.0 53.7 44.'2 3200 ft from BW discharge 31.3 25.l 61.5 46.5 TABLE 49D Study No. 4. Three baskets of young oyslers 9 lo 11 monlhs old were placed 100 feel W of tbe bleedwater discharge al Lake Barre, and four others (conlrols) were placed 2000 feel NNE of the bleedwater discharge. Each basket held 50 oysters. All oyslers were measured for length, width, and thickness. The study began on April 12, 1948, and was terminated on April 21, 1949, when ali oysters remaining were measured again. Reference: Menzel and Hopkins, 1951, Table ISA. page 33, and Table 21, page 35. April 12, 1948 April 22, 1949 No. of oyslers L Sizes, mm w T No. o! oyslers L Sizes, mm w T Yield, sacks per sack p1anted 120 ft from BW outlet 150 2000 ft from BW outlet 200 54.8 53.9 42.5 42.9 20.7 19.1 36 60 80.2 81.0 56.8 61.8 32.9 33.9 0.90 1.15 TABLE 49E Study No. 5. Oysters about 6 mooths old were placed al varying distances and directions from tbe bleedwater outlets al Lake Barre, and tbeir growth was compared with that of oyslers of the same age and origin al a distance of 3200 feet from the bleedwater discharges. Because in tbis study oyslers placed 25 to 50 feet from tbe discharges showed a definite slunting elfect, the various locations and levels are reported separately, and the number measured in· eacb case is also given. These oyslers had been in position from July 16 to November 7 before the firsl measurements were made. and the effect of the hleedwater can be seen in the first measurement. Reference: Menzel and Hopkins, 1951, Table 26, page 44, and Table 29, page 47. Number Sizes, in mm Number Sizes, in mm Distance and direction measured measured Yield, sack11 from BW outlets (feet) 11-7--48 L w T 5-17--49 L w T per sack planted Trays 2 feet above bottom 25 ft N 55 34.5 25.6 13.3 33 42.0 30.6 16.5 0.8 25ftSW 161 37.8 28.2 15.5 '1"20 37.2 '26.9 19.l 4.6 150 ft N 125 39.5 30.l 16.'Z ll5 44.0 33.4 22.4 7.0 150 ft s 190 43 .1 32.5 16.6 180 48.5 36.6 '22.4 8.6 3'200 ft s 181 45.9 35.7 18.1 163 '58.7 4ó.9 25.2 11.3 Trays 4 inches above bottom '25ft N 96 33.4 25.8 13.2 81 43.3 34.0 18.3 2.6 25 ft sw 68 31.6 23.9 12.6 12 33.3 24.0 12.1 0.4 50 ft s 16i 41.8 30.2 15.7 28 45.0 33.5 20.3 1.2 75 ft N 185 40.8 30.2 15.9 177 53.8 41.4 23.'2 9.7 75 ft s 79 43.4 32.3 18.1 75 4ó.8 34.7 23.5 9.2 100 ft s 195 42.3 32.6 17.1 183 4ó.l 34.2 22.5 8.0 150 ft N 191 45.3 34.5 17.4 174 59.9 45.8 23.8 11.8 150 ft s 194 4ó.3 34.9 17.1 156 57.'2 42.9 23.0 9.1 3200 ft s 169 46.8 37.6 18.0 142 61.0 49.4 '24.3 11.3 TABLE 49F Study No. 6. Six: Lhousand three hundred oysters of assorted sizes were placed in Sea-Rae trays al various distances and directions from the bleedwaler discharge at the Lake Barre oil field. Stalions 3200 feet and 4200 feet from the bleedwater out1et were used as control stations. Ali oysters were measured for lenglh and width of shell al Lhe beginning of the study in early August of 1947 and the survivors were measured again a year later in August, 1948. lncreases in size were computed in percenl of the original size. Mortalities were bigb and many oysters were lost in a burricane and local storms. Reference: Meozel and Hopkins, 1951, Tables 38, 39, pages 62-65. No. oysters Percenl increase Dislance from Intial No. oysters measured,BW outlet (feet) 11ize in mm August 1947 August 1948 Leogth Width Trays 2Y2 to 3 feet above bottom 80ftW 35-45 100 15 47.2 47.4 3200 ft s 35-45 100 55 85.2 80.5 80ftW 45-55 135 36 33.7 4ó.6 240 ft s 45-55 100 29 3.1 23.8 280 ft w 45-55 100 20 31.3 31.3 3200 ft s 45-55 100 '24 63.4 61.8 80ftW 55-60 100 38 28.7 32.1 3200 ft s 55-60 100 48 49 .6 47 .7 80ftW 60-70 100 41 15.3 18.8 240 ft s 60-70 100 47 9.4 10.6 280 ft w 60-70 100 27 15.5 15.1 3200 ft s 60-70 100 50 32.6 40.2 80ft W 70-80 100 37 8.8 '14.l 3200 ft s 1o_:ao 100 38 30.5 39.5 80ftW 90-105 100 26 6.9 21.4 3200 ft s 90-105 100 27 13.6 30.1 Trays 2 to 4 inches above bottom 80ft w 35-45 100 35 61.2 58.1 340 ft s 35-45 100 24 65.0 64.4 3200 ft s 35-45 100 34 62.5 68.0 80 ft s 45-55 100 30 40.0 44:.1 500 ft SW 45-55 100 35 45.6 48.8 3200 ft s 45-55 102 30 48.'l 47.5 4200ft S E 45-55 100 43 54.7 59.'2 80ft W 55-60 100 38 27.9 35.1 3'200 ft s 55-60 100 50 38.7 40.4 80ftW 60-70 100 33 23.'2 23.1 140 ft s 60-70 200 107 37.3 36.9 180 ft w 60-70 100 49 33.7 42.7 240 ft s 60-70 200 65 29.9 33.7 280 ft w 60-70 200 78 28.6 30.1 340 ft s 60-70 100 40 30.8 37.2 500 ft sw 60-70 200 78 33.4 40.2 3200 ft s 60-70 100 43 19.3 39.3 80 ft w 70-80 100 32 18.9 20.7 180 ft w 70-80 100 28 29.0 32.9 500 ft sw 70-80 100 34 21.4 26.4 3'200 ft s 70-80 100 36 23.2 15.0 4200 ft SE 70-80 100 37 25.9 30.4 80 ft w 80-90 100 21 13.1 25.6 3200 ft s 80-90 100 36 16.6 33.2 3200 ft s 80-90 200 73 20.7 38.5 80 ft w 90-105 100 17 4.6 2.9 3200 ft s 90-105 100 35 13.0 11.l 3200 ft s 90-105 100 35 9.3 29.1 TABLE 49G Study No. 7. Oysters ll lo 16 months old and averaging nearly 21,4 inches in length were placed at varyjng distances from · the bleedwater discharges al Lake Barre oíl field. al two levels: 2 feel above the botlom and about 2 to 4 inches above the bollom. These oysters were measured al tbe beginning of the study and again al lhe termination. The study began on October 15, 1948, and ended May 9, 1949, after a period of nearly seven montbs. Reference: Menzel and Hopkins, 1951, Tables 54, 59, 60, page& 94, 97, 98. :"lo. measured No. measured Percent increase in Distance and direction at start al end from BW outlet (feet) of study of study L w Th Wt Vol Tray 2 ft above bottom 25 ft N 169 67 11.6 9.0 22.2 46.4 33.0 25 ft sw 173 11 7.2 4.8 11.0 7.7 '2.0 50ft s 172 108 15.0 16.6 20.6 35.6 1.7 150 ft N 172 127 26.2 29.5 28.2 69.1 63.0 3200 ft s 175 144 28.8 28.3 30.6 70.6 68.0 Trays 2 to 4 inches above bottom 25 ft N 175 15 6.9 - 1.0 7.8 9.8 2.3 50 ft s 176 22 5.7 7.4 10.2 51.8 13.9 75 ft N 174 138 21.0 22.6 27.4 54.6 49.8 75 ft s 175 127 22.4 22.l 26.2 62.9 29.7 100 ft s 175 130 17.8 13.8 21.4 47.4 41.6 150 ft N 174 126 26.6 29.9 32.6 84.0 74.3 3200 ft s 172 142 3'1.9 41.3 31.4 85.l 8'2.5 TABLE 50 Growth of oysters exposed to bleedwater at Caillou Island Oil Field TABLE 50A Study No. l. Youog oyslers 10 to 16 months old were placed in four trays, each tra~.-conlaining 175 oyslers selecled for size, 52.S lo 67.5 mm in shell length. A sample of 508 oyslers was measured for length, widtb, and thickness on Seplember 19, 1948, and the meaos were 58 .8 by 41.4 by 24. 7 mm. Three trays were placed 100 feet from the bleedwater discbarge al the Caillou Island 6eld, but in diffcrent directions, on Septemher 19, 1948. The control tray was placed 4500 feet west. Al the end of the study on April 29, 1949, the oysters were again measured and the growlh, in percenl o{ the original size, was computed. Yields in sacks harvesled per sack planted were also computed. The data are presented in the tab1e below. Reference : Mcnzel, 1950a, Tables 16 and 17, page 23. No . oyslers P ercenl increase: Distance and direction measured al Yield írom BW discharge (reet) end of study L w T (sacks) 100 ft N 147 34.7 50.2 40.5 2.25 100 ft NE 153 27.7 34.8 38.5 2.11 100 ft s 122 23.5 33.3 34.4 1.46 4500 ft w 113 37.1 44.7 36.8 1.62 TABLE 50B Study No. 2. Selling and growtb of spat were checked in three periods in 1948 by means of chicken wire shell bags. One of the shell bag localions was 100 feet N of the Caillou Island bleedwater discharge site al the Old State-Caíllou Island tank battery. The control location was placed 4500 feet W of the BW discharge si te. Al each localion bags were al two levels. on bollom and 3 feel above. Length and width of the spal attaehing were measured in milJimeters al the end of each of the 3 periods. Re(erence: Menzel. 1950a, Table 19, page 28. 100 leel N 4500 leet W Period (1948) Oysters measured L w Oyslers measured L w -----··-­ -- ··--·- 5-2 to 7-5 3 feet above bottom 82 24.8 21.9 100 24.4 19.7 On bottom 100 24.3 19.2 70 31.0 20.0 7-5 to 9-5 3 feet above bottom llO 10.5 9.0 100 ll.2 10.3 On bottom 107 8.8 7.9 67 10.6 9.3 9-5to1-15 3 feet above bottom 99 18.0 14.6 74 19.8 16.2 On bottom 50 13.5 11.6 78 19.2 15.5 TABLE soc SLudy No. 3. On July 31, 1948, 800 young oysters aboul 21,4 months old were divided inlo four groups of 200 each, measured for length, width, and thickness of shell, for volume, and for weight. Each group of 200 was placed in one tray. Three of the trays were placed 100 feet from tbe bleedwater discharge al the Caillou Island field but in differenl direclions. The fourt.h tray of young oysters was used for a control and was placed 4500 feel wesl of Lhe bleedwater outlel. All oyslers were again measured at the end of ahoul 91,h months on May 15, 1949. Reference: Menzel, 1950a, Table 26, page 38. Percenl increase in Location Yield of station Length Width Thickness sacks 100 ft N of BW outlet 181.0 195.9 257.5 17.4 100 ft NE of BW outlet 171.3 176.4 '238.8 17.0 100 ft S of BW outlet 169.4 174.4 241.3 13.5 4500 ft W of BW outlet 170.2 183.6 237.5 16.0 STUDIES OF ACCIDENTAL LOSSES OF ÜIL Severa! studies were made which involved the measurement of effect on oysters of accidental losses of oil. lt is believed that these studies are of primary importance, since the oil was actually observed to come in contact with growing oysters and no artificial laboratory or field equipment was involved. Advantage was taken of the opportunity to study, not only the effect of crude oil losses on oysters, but also the behavior of the oil itself, its distribution, and its duration. Two studies were made by Menzel (1947, 1948). The first of these involved oysters on beds which were subtidal, and the oil therefore had to be carried clown from a surface slick, probably attached to silt particles. About 10 to 20 barreis of oil and sludge were lost as a result of an accident at the Crooked Bayou tank battery of the Texas Company. This is a large natural bayou connecting Bay Sale with Bay Coon Road and with numerous interconnecting waterways, small bays, bayous and canals. The location of the tank battery and the relations of the bayou to other water bodies are shown on the map, Fig. 38. Another oil loss occurred at almost the same time at Well 4--12, about one mile east of this tank battery. The oil from the tank battery was lost on the night of November 8-9, 1947, and the oil from Well 4--12 was lost October 29, 1947. The effect was noted on an oyster bed one mile to the north on November 9. Oysters there were inspected by Menzel and others on November 11 and found to taste oily. Severa! testing stations were set up both to the north and to the south of the origin of the tank battery oíl, and oysters were tested Fu;. 38. Site of oil losses on October 8-9, 1947 at Crooked Bayou tank battery, Bay Ste. Elaine oil field, and sampling stations set up to check on the eflect of the oil. for oily taste until it completely disappeared. The results at these stations were as follows: l. At a station 1000 feet to the north, oysters retained an oily taste to November 21 but had lost it by December 4; thus oily taste disappeared at sorne time between 14 and 27 days. However, oysters again picked up an oily taste on January 19, and retained it until February 15. Although not continuous, the oily taste in oysters at 1000 feet !asted for more than 3 months. 2. Ata station one mile to the north oysters remained oily tasting until November 14, and had no oily taste on November 21 or thereafter. At this station oily taste was retained for 5 to 12 days. 3. At a station two miles to the south, a few oysters were slightly oily in taste to November 14 and the taste had completely disappeared by November 21. Time relations are the same as for the one-mile station but the taste was definitely faint and found in fewer oysters. 4. At a mile and one-third to the south no oily taste was ever observed. 5. At a station about one mile to the east, connected by a cut canal to Crooked Bayou anda short distance from Well 4-12, no oysters were found to have an oily taste. It was evident that water movement was largely along the main bayou and did not move to any great extent through subsidiary waterways. There was no evidence that the Well 4-12 loss caused oily taste in oysters at any time. This study established that oil lost in a large waterway could be carried in quantity sufficient to make oysters taste oily for at least two miles, and that oysters a mile away could be made to have strong oily taste for a few days and sorne oily taste for a period up to 12 days. At 1000 feet, oily taste was recurrent, the recurrence probably resulting from turbulence produced by strong wind or tidal current. lt should be noted also that oíl was carried to the bottom immedia.tely. This probably resulted from the fact that a considerable part of the oil from the tank battery was sludge, i.e., weathered oil mixed with dirt. Specific gravity of weathered oil differs hut little from that of water, and with the addition of silt, it probably did not float at ali. The oysters affected by this oil loss were watched for the appearance of mortality. The strong oil taste in oysters at 1000 feet and at one mile from the oil loss proved that these oysters had been in direct contact with the crude oil. Samples were taken and "box counts" made. At the first examination it was ohserved that ali "hoxes" ( empty hinged shells) were old, i.e., they could not have resulted from the oil. lt was assumed that if mortality resulted from the contact with oil, the box percentage would increase signifi­cantly and that fresh boxes would be observed. This was not the case. Table 51 presents the data from the samples. It is realized that the percentage of boxes cannot be trans­lated into actual rate of mortality. TABLE 51 Percentage of "boxes" (empty pairs of shells attached at hinge) in samples of oysters tonged at two stations in the Bay Ste. Elaine area after an oil Ioss, 1947-1948 Percenlage of hoxes Date 1947--48 At 1000 feel Al one mile November 11 November 12 November I4 December4 December 14 December 28 January 19 February9 February 15 March8 April10 May9 June9 10.4 8.2 15.8 14.9 14.0 13.2 10.8 8.8 12.1 8.5 18.9 8.0 12.4 12.5 11.0 8.5 11.5 18.7 7.9 11.2 16.1 5.9 TABLE 52 Percentage of "boxes" in random samples of oysters tonged in various areas Location Percenlage of hoxes Bayou BasBleu '1'2.8* Bay Ste. Elaine 21.7t Bayou Du W est 17.5 Northern Barataria 37.0:t: Bastian Bay 35.2§ Chimney Bayou 21.411 Bassa Bassa Bay 7.4 Sandy Point Bay 19.7ff Bay Coquette 21.5 Skipjack Bay 23.7 Saturday Island Pickett Lake 3.1 22.7** *Average of 17 samples taken al diff'erent periods of the year. t Mean of 10 groups of box count samples each includiog 6 lo 15 individual samples. l Mean of 6 samples. § Mean of 4 samples. 11 Mean of 7 samples. ~ Mean of 2 samples. •• Mean of 5 samples. Glycogen analyses showed that these oysters remained in good condition until spawn­ing took place in the spring, when the usual radical drop occurred. Box counts have been made from samples of oysters scattered ali over the oyster­producing area of Louisiana. In Table 52 below are a few random analyses from various places, for comparison with those of Table 51. A second oil loss occurred at a well in the Bay Ste. Elaine Camp (Menzel, 1948) . This loss was about 25 barreis of crude oil which floated into the shore and into a small cove. At low tide this oil was deposited on the mud and also on a small intertidal oyster reef of coon oysters. There most of the oil adhered to mud, shells, and oysters. lt shortly assumed the weathered brown appearance. This oil loss occurred on January 3, 1948. A month later the oysters were still covered with obvious brown sticky oíl. Oily laste in these oysters remained until February 28, but by March 7 it was no longer detectable, and did not return. On January 19 the boxes amounted to 8.5 percent and on May 9, four months Iater, the count showed 5.8 percent of boxes. Exact mortality data were secured on this occasion. One thousand oysters were col­Iected from the oily mud on January 15 and placed in Sea Rae trays. These were divided into two groups, from one of which the oily mud was removed by scrubbing. These two groups of 500 oysters each were removed to Bayou Bas Bleu and observed until March 16. They both remained oily tasting until February 24. Mortalities occurred as shown in Table 53. The two groups are reported as one since the total mortality differed less than 1.0 percent in the two groups. TABLE 53 Mortality of oysters covered with crude oil by oil loss of J anuary 3, 1948, at Bay Ste. Elaine Oil Field, and removed to Bayou Bas Bleu on January 19, 1948 Date of Mortalily examinalion percent January20 0.10 January 25 0.45 January 30 0.45 February 4 0.30 February 9 o.so February 14 o.so February 19 0.00 February 24 0.20 February 29 0.20 March 16 0.10 Total mortality 2.10 An oil loss estimated at 800 barreis took place on November 5, 1951. This one was from Well 3-8 of The Texas Company's Bay Ste. Elaine Field. This well is one of a large number in a system of canals, bayous, and small bays in the marshes above Bay Coon Road. The oil lost and its effects were studied closely until ali oil had disappeared. After the loss the oil spread rapidly into the system of canals, bayous and bays to the north and west of the well under ímpetus of a strong flood tide and an equally strong south­east wind. On November 7, a strong northwest wind set in, at the beginning of an equatorial tide period. In the next severa! days tide leve! declined and varied, between high and low, only a maximum of 0.6 foot and on November 8 only 0.1 foot. During this period much of the oil disappeared; it is presumed to have been carried out into Terrebonne Bay proper via Bayou Little Caillou. The oil was not observed to go out, since much of the ebb tide period was at night. Oil was not observed in Terrebonne Bay or any of the bays intervening to the Gulf, although efforts were made to locate oil to the south of the spilled area. But the very great decrease in the canals and bayous near where the loss occurred apparently meant that flushing into the Gulf occurred during the period of high north wind. Sorne of the oil unquestionably evaporated from the water surface, and sorne was pocketed in small ponds and embayments in the marshes. It is estimated that losses to the Gulf by flushing, evaporation, and pocketing in small marsh ponds ali together removed at least 90 percent of the original 800 barreis from observable parts of the canals and bayous. The remainder of the oil adhered to the mud in the intertidal zone and attached to marsh plants. The canals and bayous in the affected zone were estimated to have at least 30 miles of shoreline. The seventy-five to one hundred barreis of oil remaining in the affected zone was distributed along these shorelines, partially in the marsh and partially in the intertidal zone. One week after the loss this oil was still visible in patches along the shore with sorne thick layers in protected places. A more or less continuous oil slick covered most of the canals and portions of interconnecting bayous and small bays as shown by the map of November 11, 1951. Oil on that date apparently reached its greatest distribution, covering a linear distance of slightly over two miles east and west and about one and one-half miles north and south. lt was observed on that date that light slicks were emerging from the shallow marsh ponds and the marsh itself, with the ebbing tide. From that date the surface slicks rapidly decreased, and it was noted that with a flood tide the canals largely cleared of oil, indicating that it was carried into the marshes and marsh ponds. On November 16 there was a strong north wind, which continued through the l 7th and shifted to the west on the 18th. By the latter date there were only small visible patches of oil on the water, in protected places. By this date weathering was largely complete and the oil, when found, was in the form of gummy brown encrustations. The "oil line" on the bordering marsh plants was still clearly visible over most of the area. There were occasional recurrences of oil slicks on the water when the wind stirred the mud in the intertidal zones. Disappearance of the visible oil did not mean that the oil was gone from the area. Portions of it sticking to the bottom along the shores could easily be found by stirring the mud in the intertidal zones, and by shaking marsh plants (Spartina mostly). A series of stations was set up by choosing those areas where large amounts of oil were observed to be pocketed along the margins. The history of one of those stations is chosen for illustrative purposes because (1) the oil ]asted longest there, and (2) there were coon oysters along the shore. This station, Number 2, was located in the margin of a shallow natural bayou about one quarter mile from the site of the original loss. Visible oil was gone from this station by November 18. However, oil could be stirred from the bottom as late as January 25, 1952. On that date, vigorous stirring produced only a slight iridescence. The original oil at Station 2 was a thick ]ayer about one-half inch thick. This accumu­lated in the first period of the oil loss. The shore line at Station 2 was so angled that the oil was piled on shore at a time when evaporation had begun to reduce it to a brown­ish tar-like sheet. lt adhered firmly to the bottom in the intertidal zone and extended into the marsh for a distance of at least ten feet, discoloring the basal part of the Spar­tina stand. At no time was it possible to stir oil from the bottom below low tide level at this station. This was true also of all other stations. This does not mean that no oil at all reached the bottom below low tide. lt does mean that the amount was so small as to be insignificant. The original thick layer of oil thinned out very rapidly. How much was removed and dispersed by water current and how much was oxidized by bacteria! action is not known. By November 18 the oil layer as such had disappeared, but heavy slicks could be stirred from the bottom at that date. Thereafter the amount rapidly decreased; the last date on which any iridescence could be produced at Station 2 was January 25, 1952. That was just a little less than three months from the time of the original oil loss. At Station 2 and located in the middle of the heaviest oil was a small oyster reef, not more than a dozen feet in diameter. When oil was at its thickest, those oysters lying flat on the bottom were completely covered. About a dozen new boxes were recovered at this time from this small reef. They were believed to have been smothered by the oil, and thus bear the distinction of being the only oysters ever observed to be killed by accidental oil loss. Those oysters standing upright were unharmed. Repeated checks of this small reef until the end of observations in late January, 1952, showed rapid growth and no additional mortality. Oil could be observed sticking to the oysters for about two months after the oil loss. Oily-tasting oysters were found at severa] stations. Those at Station 2 retained an oily taste to January 25, 1952, which was 81 days after the oil was spilled. At all other stations the period of retention of oily taste was shorter. At only one point were subtidal oysters found in the area where oil was observed. This was on an oyster lease in Ray Bayou approximately % mile north of the site of the oil loss. In this area oysters do not grow naturally below low tide, and the death rate of subtidal planted oysters is about 60 to 80 percent per year if they remain through a warm season. The oysters found were remnants of a planting which probably had been harvested. Enough live oysters were found to permit sampling for oily taste. Oil was observed over this bed and the Spartina was marked with a heavy oil line. However, no oily-tasting oysters were ever found here, even when the oil was over the bed, as it was when the first samples were taken (November 11). A close check of the fauna and flora was made during the three months of the study. At Station 2, where smothered oysters were found, a number of dead mussels, Brachi­dontes recurvus, with the meats still intact were also found. So far as could be deter­mined no other species of animal or plant was affected. Polydora, Cliona, Membranipora, Thais, Eurypanopeus, Callinectes, Balanus, gobies, and a few toad fish were found associated with the oysters. Algal growths were unaffected. In the marsh, there were thousands of Littorina, U ca, and a few Sesarma, which did not move out of the oily area. Goby eggs were particularly numerous attached to the oyster shells, especially in boxes. STUDIES ON GLYCOGEN IN ÜYSTERS TREATED WITH ÜIL AND BLEEDWATER In severa! experiments using oil or bleedwater, glycogen analyses were made on oysters at the end of the study, comparing controls and experimental oysters. The results of studies in the Grand Isle Laboratory and the Barataria Bay area are presented in Table 54, and the results of studies in Bay Ste. Elaine and Lake Barre oil fields are summarized in Table 55. For Table 54, the references are: Mackin, 1948a, page 18; TABLE 54 Summary of studies on the effect of oil or bleedwater on glycogen content of oysters in the Barataria Bay area Oil or bleedwaler Glycogcn, percenl ol wet weight application Experimenl Cont..-ol Remarks Oil sprayed on oysters in field for 6 months Oil sprayed on oysters in field for 6 months Emulsified oil applied in laboratory for 6 months Heavy applications of emulsified oil over a period of 8 days to 2 weeks; observed for 6 or 7 months in field Bleedwater in concentrations of 1% and 2.5% applied in aquaria for 6 months Means 3.78 4.19 0.174 8.62 1.47 1.62 3.252 6.10 5.36 0.292 7.89 1.40 0.815 3.643 Only 8 oysters analyzed About 60 oysters in each sample lnadequate number of survivors for depend­able check 60 oysters in each sample Aquaria treated with bleedwater developed heavy blooms of diatoms and other alga] forms TABLE 55 Summary of field studies on the effect of bleedwater on glycogen content of oysters in oil field areas Glycogen, percenl of wet weight Period Distance from Sludy No. studied BW oullets At st.art Alend B. Ste. E. Dec. 1947­ 200 ft 2.29 5.04* No. l Jan. 1949 1 mile 3.53 3.88* B. Ste. E. Aug.1947­ Between outlets 0.93 1.66 No.2 Aug. 1948 2160 ft 0.93 1.20 B.Ste. E. Sept.'1948­ Between outlets 5.59 No.3 Apr. 1949 2160 ft 6.64 L. Barre Jan. 1948­ 80 ft, top trays 3.04 1.32 No. l Aug. 1948 80 ft, bottom trays 1.85 1.56 3200 ft, top trays 3.84 1.08 L. Barre Oct. 1948­ 3200 ft, bottom trays 25 ft north 3.73 1.22 0.557 No.2 May 1949 50 ft south 0.568 100 ft south 1.540 150 ft south 1.740 3200 ft south 2.370 *Tbese commercial boltom planlings were sampled monthly; glycogen percenl ftuctuated from 1.29 to 6.70 in the experimental plot and from 1.02 to 5.02 in the control plot. Tbis may be compared with the range from 1.71 to 6.11 in Bayou Bas Bleu during the same period. 1948b, page 3; 1948e, page 5; 1949, page 4; 1950a, page 3. For Table 55, the refer­ences are: Menzel and Hopkins, 1951, pages 62, 95; 1952, page 124; 1953, pages 59-60 and 144, 149. STUDIES ON THE EFFECT OF NATURAL GAS FROM DEEP WELLS ON MORTALITY, GROWTH, AND GLYCOGEN CONTENT OF ÜYSTERS As natural gas leaking from pipe lines had been mentioned by sorne oystermen as a possible cause of oyster mortality, three field tests on the effects of deep well gas were conducted at Bay Ste. Elaine oil field by Menzel (1949). Waste gas here was discharged under water at the rate of five cubic feet per minute. Oysters in wire baskets were placed at the gas outlet and at various distances. The mortality, growth, and change in glycogen content of experimental and control oysters are shown in Table 56. For details see the original report (Menzel, 1949 ) . TABLE 56 Effect of natural gas on mortality, growth, and glycogen content of oysters Glycogeo. pcrcent Percenl of wel """f'ighl Study Test Morlality increase in no . period percent sbell length Start End Aug.1947­ Exper.• 9.6 80.8 Jan. 1948 Controlt 7.0 37.3 2 Apr.1948­Sept. 1948 Exped Controlt 41.7 42.5 13.9 20.5 Exper.§ 3 Mar. 1949­May 1949 Group 1 Group 11 8.0 22.7 -1.12 3.09 5.50 2.97 2.75 2.87 Controlll Group 1 Group 11 8.0 16.0 0.25 6.51 5.50 2.97 4.20 3.39 • Averages of baskets under gas exhaust. al four locations 10 feel away. and al four locations 25 feet away. t Control baskets were 3500 feet north of gas outlet. t A verages of one basket under gas exhaust and four 10 feet away. § Experimental oysters were in a wooden box with hardware cloth top and hottom, enclosing the gas oullet so that gas bubbled up through the oysters. The two groups were of different sizes and origins. 11 Control oyslers were in an identical box withoul gas 36 feet away. ExPERIMENTS WITH CoMPONENTS oF DRILLING Muo In rotary drilling, a heavy fluid mixture known as drilling mud is pumped down through the hollow drill stem to cool the bit, coat the walls of the well, and prevent gas blow-outs; it returns to the surface through the space between the drill stem and the walls of the well, bringing with it the rock cuttings from the bit. After cuttings are screened out for geological study, the used drilling mud from a barge-mounted drilling rig may be dumped into a mud barge for disposal or to be processed for reuse, or it may be dumped overboard. Drilling mud is therefore among the products of oil operations that have been suspected of killing oysters. In a study of the effect of barium sulphate, the principal chemical constituent of drilling mud, one sack of Magcobar was used to bottom the experimental aquarium (60 by 95 cm) to a depth of about 4 to 5 cm. Water covered the Magcobar to a depth of 10 cm, and experimental oysters were placed on the drilling mud. A mud-sand mix­ture bottomed the control tank. The water flow was 500 cm per minute in both tanks (Table 57). TABLE 57 Results of drilling mud experiment, testing the effect of barium sulphate on oysters, December 10, 1949 to April 10, 1950 Reference : Mackin, 1950d No. of ~umber Percenl oyslers dead de ad Experiment 30 2 6.7 Control 30 3 10.0 Quebracho, powdered bark from the "axe breaker" tree of South America, is used in the leather tanning industry for its high tannin content. It is also an important con­stituent of many drilling mud mixtures. Six laboratory experiments to test the effect of quebracho on oyster survival were carried out at Grand Isle. A stock solution of 100 grams of quebracho (dry powder) in 20 liters of sea water was prepared. This gave a dark wine-red mixture, part solution and part suspension of fine particles. The stock solution was dripped into experimental aquaria in controlled amounts and the sea water flow was maintained at 2000 ce per minute in all aquaria. Experiments were run in two sets of three, each set with one control (Table 58). TABLE 58 Tests of the effect of quebracho on mortality of oysters Reference: Mackin, 195lb Concenlration No. oyslers Number Percent of Quebracho used dead de ad Results of first set of three experiments, August 6, 1950 to 'September 21, 1950 1/ 10 stock 15 9 60.0 l /20 stock 15 8 53.3 1/40 stock 14 6 42.9 Control 15 8 53.3 Results of second set of three experiments, October 9, 1950 to June 9, 1951 1/10 stock '15· 5 33.3 1/5 stock 15 5 33.3 2/3 stock 15 10 66.7 Control 15 5 33.3 STUDIES ON SEISMOGRAPHING ANO JTS EFFECT ON ÜYSTERS The first studies of the effect of seismographic exploration on oysters were described in the report of the Louisiana Department of Wildlife and Fisheries for 1938-1939 (McConnell, 1949). The experiments were carried out by L. D. Kavanaugh of the Division of Water Bottoms. Details were not given, except that the shots were on the bottom, at distances of 175 to 750 feet from experimental oysters, and shots of 30 to 70 pounds of "high velocity" gelatine were used. These studies were not conclusive, and mortality data were not given. McConnell (1944) stated that the seismic division had investigated the effects of seismic exploration further, but no report has been published. Gowanloch and Mc­Dougall (1944) found that 800 pound shots on the bottom failed to harm oysters at 50 feet. The same authors (1945) again set up experiments to test the effects of heavy charges (up to 400 pounds) . These charges were sunk 25 feet below the surface of an oyster bed. No mortality resulted in the six weeks that experimental oysters were kept under observation. Sieling (1954) quoted an anonymous report of the Chesapeake Biological Laboratory which stated that 2 percent of oysters exposed in bags on the bottom within 100 feet of a 30 pound suspended charge, and within 200 feet of a 300 pound charge were killed immediately and 5 percent were fatally injured. Kemp (1954) found that 40 pound shots placed 20 feet below the bottom killed oysters as far out as 200 feet. The data from the experiments reported by Kemp appear to be contradictory: in the study which showed that oysters were affected at 200 feet, fish, shrimp, and blue crabs were unaffected at 10 feet; in anothe~ study where oysters were said .to be affected at 50 feet, fü.h, shrimp, and blue crabs were not affected at less than 5 feet (at the shot point). Kemp's results seemed to directly contradict Gowanloch's. STuorns BY THE REsEARCH FouNDATION Experiments by the Research Foundation were designed to test immediate and/or delayed effects of seismographic exploration on oysters. Effect of shock, effect of gases liberated from the bottom, and effect of explosives in causing oysters to sink in soft bottom, were ali investigated by Sieling (1951, 1954). He set up two studies, one in Bay Baptiste, a northeast extension of Barataria Bay, and the other in Hackberry Bay, just to the northwest of Barataria Bay. Oysters were held in trays, which were placed at measured distances of 20, 60, 130, and 250 feet from a shot point in a staggered line. This shot point was flanked in four directions by additional shot points 1000 feet from the central one. Controls were set up 750 feet from the nearest shot point. Bottom plant­ings were made at 40 feet from each central shot point, in staked areas 18 feet square. Distant controls were placed at Bay Chene Fleur and in mid-lower Barataria Bay. The Chene Fleur station had a lower salinity than the experimental areas and the Barataria Bay stations were in higher salinity waters. Explosive charges of 50 pounds at 70 feet deep, and 20 pounds at 30 feet deep, were discharged at each shot point. The five stations of a shot point group were fired succes· sively, as fast as the field crew could make the necessary connections. Trays at the Bay Baptiste experimental and control stations were placed on the bottom, while at Hack· berry Bay the tray oysters were held on racks. Chemical measurements were made immediately before the experimental shots, im­mediately after the shots, and at intervals for severa} months. Oysters at each station were examined immediately before and immediately after the shots to determine whether shock effects were present. One day later, part of the oysters of each control station were moved to the experimental area (5 trays, one at each measured distance from the shot point). Similarly, trays from the experimental stations were moved to the control stations. These shifts were designed to detect delayed effects, as distinguished from shocks effects, if any were present. Checks at experimental and control stations were made thereafter at approximately two-week intervals for eight months, except for sorne trays which were stolen from Hackberry Bay station. Results of these studies are presented below in Tables 59 and 60 from Sieling (1954). TABLE 59 Results of experiment testing the effect of seismographic exploration on oysters in Hackberry Bay No. No. oyslers Percent No. oysters Percenl Distance from oysters surviving 4. survival 4 surviving 8 survival 8 central shot poinl started* monlhst months monthst months Rack # 1, 20 fe et Permanent Trays 345 289 83.7 From Chene Fleur 172 157 91.2 From Station 51 155 92 59.3 Rack #2, 60 feet Permanent Trays 348 302 86.7 From Chene Fleur 172 152 88.3 From Station 51 166 100 60.2 Rack #3, 130 feet Permanent Trays 336 287 85.3 From Chene Fleur 170 147 86.5 From Station 51 156 73 46.8 Rack #4, 250 feet Permanent Trays 333 281 84.4 From Chene Fleur 170 156 91.7 From Station 51 162 96 59.2 Controls in Hackberrr Bar Permanent Trays 338 257 76.0 From Chene Fleur 169 133 78.6 From Station 51 163 86 52.8 Controls at Chene Fleur Permanent Trays 864 789 91.3 761 88.1 From Rack 1 172 150 87.2 136 79.l From Rack 2 171 14S 86.8 141 82.5 From Rack 3 168 152 90.4 144 85.7 From Rack 4 173 151 87.3 143 82.6 From Control Rack 171 146 85.4 140 81.9 Controls at Station 51 Permanent Trays 825 625 75.8 567 68.7 From Rack 1 lM 139 84.7 123 75.0 From Rack '2 169 143 84.6 132 78.1 From Rack 3 169 137 81.0 121 71.6 From Rack 4 169 132 78.1 116 68.7 From Control Rack 166 142 85.5 126 75.9 *Permaneot lrays al Station 51 slarted 8-20-49. trays al Cbene Fleur slarted 8-19-49, all other trays started 8-23-49. t Dates taken as end of 4 months period were 1-5-50 for controls at Station 51 and 1-9-50 for ali other trays. t Dates for end of 8 months period were 4-22-50 for Station 51 and 4-23-50 for Chene Fleur. TABLE 60 Results of experiment testing the effect of seismographic exploration on oysters in Bay Baptiste No. oysters Percent Distance from ~o. oysters surviving 71h SUr\'ÍVal central shot poinl started* moothst 71hmonths Rack # 1, 20 feet Permanent Trays 334 253 75.7 From Chene Fleur 168 134 79.8 From Station 51 143 105 73.4 Rack #2, 60 feet Permanent Trays 326 256 78.5 From Chene Fleur 164 131 79.9 From Station 51 127 lll 87.4 Rack #3, 130 feet Permanent Trays 324 255 78.7 From Chene Fleur 166 127 76.5 From Station 51 151 108 71.5 Rack #4, 250 feet Permanent Trays 329 242 73.5 From Chene Fleur 164 129 78.6 From Station 51 14S lll 75.0 Control Bar Baptiste Permanent Trays 341 264 77.4 From Chene Fleur 170 133 78.2 From Station 51 150 118 78.6 Controls at Chene Fleur Permanent Trays From Rack 1 834 159 736 139 88.2 87.4 From Rack 2 166 138 83.l From Rack 3 128 97 75.7 From Rack 4 165 143 86.7 From Control Rack 171 139 81.3 Controls at Station 51 Permanent Trays From Rack 1 820 164 5% 121 72.7 73.7 From Rack2 167 ll2 67.0 From Rack 3 167 104 62.2 From Rack4 166 120 72.2 From Control Rack 170 109 64.l • Permanent trays at Chene Fleur started 8-30-49, all olher trays 8-31-49. f 7112 months ended 4--22-SO for Stalion 51, 4-23-50 for Chene Fleur, and 4-21-50 for Bay Bapti5te. These experiments showed no effect of shock, no delayed mortalities, and no change in the bottom caused by the explosions. The numbers of oysters used were great enough that there is no question as to the statistical reliability of the studies. Kemp's studies cited above were definitely faulty in that respect. Sieling found no immediate gaping of oysters checked immediately after the shots were fired. The period of observation was longer than in any previous test of the effect of explosions. However, in Gowanloch's study the oysters removed to a distant station after the shots were observed long enough for practica! purposes. Summary and Conclusions l. The history of the oyster industry shows that Louisiana oysters have always been subject to high rates of mortality, and that periods of disastrously high mortality have been frequent as far back as the records go. 2. Louisiana oyster production statistics indicate that the period 1940 to 1947, when catastrophic mortality caused by oil operations was alleged in law suits, was in fact the most productive eight-year period in the history of the Louisiana oyster industry. The official figures show a mean annual production of more than 850,000 barreis of oysters during this period. 3. The same figures show that oyster production declined in the state as a whole during the period 1940 to 1947, so that the last four years (1944 to 1947) hadan average annual production of only about 635,000 barreis. A sharp drop in production in St. Bernard Parish, according to the official Louisiana statistics, was responsible for the greater part of this decline. St. Bernard Parish is far outside of the area where dam­age from oil operations was claimed. 4. The study of Louisiana oyster production statistics and oyster history showed that disastrously high mortality of oysters had occurred at times both before and after oil production began in the oyster-growing area, and that since oil production started there had been oyster mortalities in places far distant from oil operations as well as in and near oil fields. 5. Numerous accounts in the literature, including official reports of Louisiana state agencies concerned with management of the oyster industry, have linked high mortalities in the past with high salinity of the water over the beds. 6. Field studies of Texas A&M Research Foundation biologists, beginning in 1947, confirmed reports that mortality rates were high on many Louisiana oyster beds, and that there was a seasonal cycle in mortality correlated with temperature. Except during abnormally warm periods there was little mortality in winter, but oysters began to die in spring and continued to die steadily all summer and into autumn until stopped by cool weather. The regular and predictable nature of this mortality indicated that it was not abnormal. The general picture was, rather, that a high rate of mortality associated with summer temperatures was normal in much of the Louisiana oyster-growing territory. 7. Field studies of Foundation biologists also showed that within the region where damage from oil operations was claimed (in general, Placquemines, Jefferson, La­fourche, and Terrebonne Parishes) there were areas where oyster mortality was con­sistently low as well as areas of high mortality. No correlation was found between rates of mortality of oysters and their proximity to oil fields. lndeed, in the Barataria Bay area where most damage to oyster production was claimed, the highest mortalities were found at the stations farthest from centers of oil and bleedwater production. On the other hand, high mortality was found to be correlated with high salinity of the water. 8. Extensive studies by Texas A&M Research Foundation chemists have shown that measurable amounts of substances which are extractable with carbon tetrachloride, and are unsaponifiable, are present in natural muds of water bottoms far removed from any source of oil pollution as well as near oil fields. Unsaponifiable carbon tetrachloride extractives have been called "hydrocarbons" by sorne chemists without further attempts at identification. However, Foundation chemists found that the quantity of so-called "hydrocarbons" was correlated with amount of plant debris in samples, and that such substances could be cxtracted from aquatic plants. 9. The quantity of so-called "hydrocarbons" in mud samples taken from bottoms, including oyster beds claimed to be damaged by pollution, in high mortality areas was no greater than in muds from low mortality areas. 10. Studies of mud samplcs taken in oil fields at and near bleedwater outlets, in sorne cases showed quantities of unsaponifiable carbon tetrachloride extractives far greater than any found elsewhere, and these samples were also. shown by Horvitz to have quantities of substances identified as "pentane and heavier hydrocarbons" greater than any found at points distant from oil production centers. However, these quantities diminished rapidly with distance away from points of effiuent discharge. In no case was oil from a bleedwater outlet traced to an oyster bed, although intervening bottoms were sampled diligently. 11. Analyses of many water samples also showed that substances identifiable by uncritical routine analysis as "hydrocarbons" are found in minute quantities in Louisi­ana hay waters, and that quantities of such substances are no higher in arcas of high oyster mortality than in low mortality arcas. Much larger quantities are found in bleed­water effiuents, but in natural waters into which the bleedwater discharges the amounts are negligible, rapidly decreasing with distance away from the point of discharge and soon dropping to the barely detectable leve] found in ali hay waters. 12. Calculations based on the actual production of bleedwater in Louisiana oil fields, and the volumes of water in bays, have shown that oil from this source could not possibly reach a significant leve! of concentration in oyster-growing hay waters, or in bottoms of these water bodies, even if none were destroyed. 13. Bacteriological studies have shown that crude oil and fractions of crude oíl are rapidly oxidized and destroyed by bacteria which live in Louisiana bay muds. 14. Studies of a few cases of accidental spillage of crude oíl in oyster-producing waters have shown that such oil losses may cause an oily taste in oysters in the vicinity, but the oysters rid themselves of thc oily taste in a few days or weeks, depending on the degree of contamination and other factors. With the exception of one case where a heavy oil deposit apparently smothered a few intertidal oysters, no mortality of oysters resulted from the oil losses studied. 15. The only studies by any previous investigator that indicated oysters could be killed by small amounts of crude oil or oil extracts were those by Gowanloch in 1933. Biologists of the Texas A&M Research Foundation carefully repeated Gowanloch's laboratory experiments and failed to confirm his results. The survival of oysters was not affected by oil in exact duplicates of Gowanloch's experiments. 16. Other laboratory studies by Foundation personnel on the effect of bleedwater, crude oil, and extracts (so-called "soluble fraction") of oil on survival of oysters, using concentrations of pollutants greater than could occur on oyster beds, have given uni­formly negative results. 17. Laboratory studies by Foundation personnel and consultants on the physiological effects of crude oil, "soluble fractions" of crude oil, and bleedwater have shown that a detectable effect on activities of oyslers is not produced by any concentration of oil or bleedwater that can occur in oyster-producing waters (bays or bayous) of Louisiana. Physiological effects (slowing of water pumping and filtering activity) were caused by amounts far in excess of any concentration possible in the waters over an oyster bed. These effects did not result in harm to the oysters, and were completely reversible. 18. Field experiments in Barataria Bay showed that spraying oysters repeatedly with crude oíl and keeping oysters under a surface !ayer of crude oil did not affect survival or growth. 19. At Lake Barre Oíl Field, where the amount of bleedwater discharged directly into an oyster-producing water body was greater than at any other place in Louisiana, field experiments showed that oysters were killed by bleedwater. However, this Iethal effect extended only to a distance of 50 to 75 feet from the point of discharge. Shell growth and accumulation of glycogen in oysters were adversely affected to a distance of approximately 150 feet from the bleedwater outlets, but there was no harmful effect at greater distances. 20. Other experiments, including field experiments on setting, growth, survival, and fattening of oysters at various distances from bleedwater and waste gas outlets in various oil fields, failed to show any harmful effect of oíl, bleedwater, or natural gas. 21. Laboratory experiments showed that barium sulphate and quebracho, principal constituents of drilling muds, have no lethal effects on oysters in concentrations that could be maintained in water over an oyster bed. Barium sulphate is insoluble and inert, and has no toxic properties. Quebracho is toxic at concentrations higher than those possible in natural waters. 22. Field experiments showed that high explosives discharged in boles drilled in the bottom, in the manner prescribed by Louisiana law for seismographic exploration in enclosed waters, did not affect oysters in any way. 23. We conclude from the history of Louisiana oyster production, and from Foun­dation studies in the field and laboratory, that oil operations could not have been responsible for widcspread mortalities of oysters as alleged. Those widespread mortali­ties which actually occurred during the period of our studies resulted from moderately but persistently high daily mortality rates which were associated with high temperatures and high salinities, and were preventable by decrease in either temperature or salinity, entirely independent of oíl operations. Literature Cited An asterisk ( *) indica tes the unpublished reports in depositories of the 28 libraries listed in the preface to this volume. Alexander, M. L. 1922. Report of the Commissioner of Conservation. Fifth Biennial Report, Depart· ment of Conservation, State of Louisiana, for 1920-22, p. 7-17. Allee, W. C., A. C. Emerson, Orlando Park, Thomas Park, and Karl P. Schmidt. 1950. Principies oí animal ecology. W. B. Saunders Co., New York, XII, 837 p. Anonymous, 1906. Secretary's Report, Second Biennial Report of the Oyster Commission of Louisiana for 1904-1906, p. 15-17. Anonymous, 1940. Seismograph-oyster project. 14th Biennial Report. Department of Wildlife and Fisheries, State of Louisiana, 1938-1939, p. 320-3'22. Austin, George B. 1955. Current survey West Barataria Bay, Louisiana. Report to The Texas Company, dated March 18, 1955 with supplement. Barlow, John P. 1955 A survey of the distribution and characteristics of fresh and brackish water in Barataria Bay and its tributaries. Texas A and M Research Foundation, Project 120. Baylor, J. B. '1904. Report addressed to the Oyster Commission of Louisiana. First Annual Report of the Oyster Commission of Louisiana, 1902-1904, p. 73-81. Bench, Bernard M. 1947. Bacteria! activity and its relation to petroleum. The Mines Magazine. November, 1947, p. 50. *Boswell, J. L. 1950. The effect of crude oil on oysters (Gowanloch method) Texas A and M Research Foundation, Project Nine, July 6, 1950. Breaux, J. M., Ben Michell, Horace H. Harvey, Clement Story, and A. E. Hoffman. Third Biennial Report of the Oyster Commission of Louisiana, 1906-1908, p. 3-11. *Brown, S. O. 1950. Microbial oxidation of crude oils and water soluble fraction of crude oil as shown by the B. O. D. method. Texas A and M Research Foundation, Project Nine. *Brown, S. O. and Virginia Van Horn. 1950. Aerobic and anaerobic oxidation of crude oils by microorganisms from Louisiana bay-bottom muds. Texas A and M Research Foundation, Project Ni ne. *Brown, S. O., Virginia Van Horn and Bobby L. Reid. 1950. Decomposition of organic compounds by marine microorganisms. Texas A and M Research Foundation, Project Nine. Cage, Harry. 1904. Report of the Chief Inspector, Oyster Commission of Louisiana. First Annual Report, Oyster Commission of Louisiana, 1902-1904, p. 21-29. Cary, L. R. 1906. The conditions for oyster culture in the waters of the parishes of Vermilion and Iberia, Louisiana. Gulf Biologic Station Bulletin 4: 6-27. Cary, L. R. 1907a. The cultivation of oysters in Louisiana. Gulf Biologic Station Bulletin 8: 4-56. Cary, L. R. 1907b. A preliminary study of the conditions for oyster culture in the waters of Terrebonne Parish, Louisiana. Gulf Biologic Station Bulletin 9: 4-62. Chipman, Walter A. 1942. Progress report on investigations of oyster mortality in Barataria Bay, Louisiana, for the summer of 1942. Typed Report, U. S. Fish and Wildlife Service, Pensacola, Florida. Collier, Albert, 1953. Oysters, their growth rate and survival when retained under crude petroleum, p. 1-156. Collier, Albert, S. M. Ray, and Wayne Magnitzsky, 1950. Preliminary note on naturally occurring organic substances in sea water affecting feeding of oysters. Science 111 (2876) : 151-15·2. Dymond, John, Jr. 1904. The oyster in Louisiana. First Annual Report, Oyster Commission of Louisiana, 1902-1904, p. 83-107. Galtsoff, Paul S. '1942. Urgent oyster problems in Louisiana. Typed Report, Shellfishery lnvestiga­tions, U. S. Fish and Wildlife Service. Galtsoff, Paul S., H. F. Prytherch, R. O. Smith, and Vera Koehring, 1935. Effects of crude oil pollution on oysters irí Lt•uisiana waters. Bulletin 18, U. S. Bureau of Fisheries. 48: 143-210. Gates, W. H. 1910. A few notes on oyster culture in Louisiana. Gulf Biologic Station Bulletin 15, p. 5-32. Gowanloch, James Nelson. 1934. Oyster beds and oil wells, a complex conservation problem. Louisiana Conserv. Rev. 4(2): 47-48. Gowanloch, J. N. 1936. Pollution by oil in relation with oysters. Twelfth Biennial Report, Depart­ment of Conservation, State of Louisiana, 1934-35, p. 239..:246. Gowanloch, J. N. and John E. McDougall. 1944. Louisiana experiments pave way for expanded oil research. Louisiana Conserv. Dec., 1944, p. 3 and 6. Gowanloch, J. N. and John E. McDougall. 1945. Dynamite·oyster experiments provide far-reaching results. Louisiana Conserv. Aug. 1945, p. 5 and 8. Gowanloch, J. N. 1946. Report of activities related to the oyster problem. First Biennial Report, Department Wildlife and Fisheries, State of Louisiana, 1944--45, p. 194-209. Gulf Fisheries, 1956. Department of the Interior, Fish and Wildlife Service, CFS No. '1746, Annual Summary, p. 1-6. Gunter, Gordon. 1949. A summary of production statistics and facts related to development of the oyster industry of Louisiana, with a brief comparison with other Gulf states. Pub. No. 2. Texas A and M Research Foundation. Gunter, Gordon. 1952. Historical changes in the Mississippi River and the adjacent marine environ· ment. Pub!. lnst. Mar. Sci. Univ. Tex. 2 (2): 121-139. Gunter, Gordon, 1955.. Mortality of oysters and abundance of certain associates as related to salinity. Ecology 36 (4): 601---019. Hancock, C. K. 1949. Countercurrent Barataria Bay water extracts of LaFitte "clean" petroleum. Texas A and M Research Foundation, Project Nine. Hesse, R., W. C. Allee, and K. P. Schmidt. 1937. In Ecological animal geography, p. 36-37. Wiley, New York. Hewatt, W. G. 1949. A summary of hydrobiological conditions in Barataria Bay and related waters. July, 1945-September, 1947. Texas A and M Research Foundation, Project Nine. Hewatt, W. G. 1950. Studies on bleedwater dispersa! in the natural waters around oíl fields in southern Louisiana. Texas A and M Research Foundation, Project Nine. *Hewatt, W. G. 1951. Salinity studies in Louisiana coastal embayments west of the Mississippi River. Texas A and M Research Foundation, Project Nine. *Hewatt, W. G. '1953a. Climatological and hydrological records of the Barataria Bay area, Louisiana, Part II, Figures. Texas A and M Research Foundation, Project Nine. *Hewatt, W. G. 1953b. Ecological studies on salt marsh ponds in southem Louisiana. Texas A and M Research Foundation, Project Nine. Hewatt, W. G. 1955. Climatological and hydrological records on the Barataria Bay area, Louisiana. Texas A and M Research Foundation, Project Nine. Hopkins, A. E. 1947. Transcript of field notes taken by Dr. A. E. Hopkins of the U. S. Fish and Wildlife Service, February 11 to February 15, 1957, in Louisiana waters in cooperation with officials of Louisiana Department of Wildlife and Fisheries, and representatives of Oyster Commission. Jakkula, A. A. 1947. Organization of project to determine causes of oyster mortality (as of July IS, 1947). Texas A and M Research Foundation, Project Nin e. Jakkula, A. A. 1948. Notes on functions and duties to accompany organization and personnel chart of Research Project Number 9. Texas A and M Research Foundation, Project Nine. Jensen, Fred W. 1948a. Memorandum on the effect of bleedwater on the salinity in Barataria Bay. Texas A and M Research Foundation, Project Nine . .Tensen, F. W. 1948b. Report of the meeting of the Technical Committee August 13-14, 1948. Texas A and M Research Foundation, Project Nine . .Tensen, Fred W. 1949. No title or text. A series of graphs showing oxygen and redox potential measurements in Barataria 'Bay, taken in 1948. Texas A and M Research Foundation, Project Nine. Jensen, Fred W. 1950. The production oí bleedwater and crude oíl in the Barataria Bay Watershed, 1941-1946; composition of the bleedwaters, and possible pollution effects of bleedwaters and crude oils on Barataria Bay. Texas A & M Research Foundation, Project Nine. *.Tensen, Fred W., and W. M. Potts. 1953. Mud samples and analyses. Pt. 11. Volatile hydrocarbons, carbon tetrachloride extract and unsaponifiable residues in muds. Texas A & M Research Foundation, Project Nine. Kemp, R. J., Jr. 1956. Do seismograpbic explosions affect marine life? Texas Game and Fish, Sept., 1956, p. 11...:13, Krumbein, W. C. and Esther Aberdeen. 1935. The sediments of Barataria Bay. J. Sediment. Petrol. 7: 3-17. Lund, E. J. 1949. Effect of bleedwater, soluble fraction, and crude oil on the oyster. Texas A & M Research Foundation, Project Nine. Lund, E. J. 1957. Effect of bleedwater, "soluble fractions" and crude oil on the oyster. Pub. Inst. Mar. Sci. Univ. Tex. 4(2): 328-341. *Lunz, G. R. 1950. The effect o.f bleedwater and of water extracts of crude oil on the pumping rate of oysters. Texas A & M Research Foundation, Project Nine. Mackin, J. G. 19'48a. Report on the first spraying experiment. Texas A & M Research Foundation, Project Nine. Mackin, J. G. 1948b. Report on the second spraying experiment. Texas A & M Research Foundation, Project Nine. Mackin, J. G. 1948c. Report on tbe third spraying experiment. Texas A &M Research Foundation, Project Nine. Mackin, J. G. 1948d. A study of the effect on <>ysters of a heavy surface water !ayer of crude oíl. Texas A &M Research Foundation, Project Nine. Mackin, J. G. 1948e. Report on a study of the effect of subjecting oysters to continuous applications of emulsified crude oil. Texas A & M Research Foundation, Project Nine. Mackin, J. G. 1948f. Report on a study to determine the effect of subjecting oysters to continuous contact with oil soaked mud. Texas A & M Research Foundation, Project Nine. Mackin, J. G. 19 characters of D. marinum indicated that if it was F1G. 7. Sketches of enlarged D. marinum cells in oyster serum, unstained, 25 to 40µ. A, D, F. Rare, enlarged cells produce tube-like processe.3 from which small cells may be detached. A, C, F. Cleavage of the cytoplasm. B, E. Enlarged cells without modification except enlargement, and development of fatty granules. not a yeast-like component of one of the higher Phycomycetes or Ascomycetes, it must belong to one of the fungal groups in which mycelia are wholly lacking. This concept greatly narrowed the field of possibilities so far as recognized groups are concerned. Based on the work by Prokop and Ray, it seemed probable that an excess of nutrient material was being applied in attempts to culture. Only if D. marinum was one of the higher fungi would large concentrations of nutrient be needed. The first step in attempts to culture were therefore made with fluid thioglycollate medium in various dilutions clown to 1/ 100 normal strength. The first tria! was successful in producing sorne re· production. The data from this attempt are condensed in Table l. The methods were as follows: (1) Normal strength fluid thioglycollate medium required 29.5 grams per liter of nutrient material. This concentration in Table 1 is termed a 1.0 concentration. TABLE 1 Results of attempts to culture D. marinum using various dilutions of the standard fluid thioglycollate medium. NaCI was added to these cultures to produce about a 20 ppt medium, and penicillin and streptomycin were added to ali cultures Trial 1/2 1/5 Concenlralion of fluid thioglycollate medium 1/ 10 1/25 1/50 1/100 Ali cells enlarged Ali cells enlarged Enlarged; contaminated No D. marinum cells found Few reproducing D.marinum; contaminated Moderate no. of reproducing D. marinum ; contaminated Rare reproducing D. marinum cells found contaminated 2 Ali cells enlarged Ali cells enlarged No D. marinum cells found No D. marinum cells found Reproduction of D. marinum heavy Reproduction of D. marinum heavy Reproduction heavy; contaminated 3 Ali cells enlarged Ali cells enlarged; not contaminated No D. marinum cells found; contaminated No D. marinum cells found; ~ontaminated Moderate no. of reproducing D. marinum; contaminated Reproduction heavy; contaminated Few reproducing D. marinum; contaminated 4 Ali cells enlarged Ali cells enlarged; not contaminated Enlarged Rare reproducing D. marinum cells; contaminated Moderate no. of reproducing D. marinum; contaminated Moderate no. of reproducing D. marinum; contaminated No D. marinum ce lis found; contaminated 5 Ali cells enlarged Ali cells enlarged; ali dead No D. marinum cells found No D. marinum cells found Few reproducing D. marinum Few reproducing cells found; contaminated No D. marinum cells found; contaminated (2) The effect of various concentrations of potassium iodide was also tested in this series. Since no effect was demonstrated, no data are reported. (3) Volumes of fluid thioglycollate medium, K 1, antibiotics (pencillin and strepto­mycin) and homogenate of infected oyster tissue were so mixed to produce 10 ce of inoculated culture medium per screw cap tube. ( 4) Tissue from a gaping oyster was carefully broken up in a Waring Blendor. The resulting homogenate was strained through multiple thicknesses of cheese cloth to re­move excess tissue. Counts of D. marinum cells were made from 10 aliquots of this homogenate and averaged. Counts were made with a standard haemocytometer. The homogenate was then diluted to contain approximately 200,000 D. marinum cells per ce of homogenate. One ce of the homogenate was introduced into each of 35 screw cap culture tubes which contained various concentrations of fluid thioglycollate medium as shown in Table l. (5) Culture tubes were kept at "room temperature," 25° to 30°C, approximately. (6) Study was begun on July 6, 1954, and the tubes were examined on July 13, 1954 and subsequently on July 17, 1954 when the study was completed. The data from this study (Table 1) showed that enlargement did not occur in dilutions of 1/ 10 to 1/ 100 strength. One culture of 1/ 10 strength showed a few reproduc­ing D. marinum, but no D. marinum cells were recovered in four cultures. In all 1/ 25 and 1/ 50 strength cultures reproduction took place, and good cultures developed in a few tubes. Only one of the 1/ 100 strength cultures was successful, this one producing very good reproduction. Overall the 1/ 50 strength cultures were rated best with two fair and two very good reproducing tubes. Most of the cultures produced in dilute fluid thioglycollate medium were contami· nated, either with bacteria or with filamentous fungi, mostly Fusarium. In those cultures in which bacteria developed D. marinum failed to reproduce, although enlargement occurred under conditions of bacteria! contamination. When fungi were contaminants they appeared to have no effect on reproduction. Ali cultures were dead or moribund eleven days after initiation. Examination showed that the fungus cells in 1/ 25 to 1/ 100 dilutions, without bacteria, reproduced more or less rapidly for about a week and then died. However, any reproduction at ali was a step forward and was regarded as having bolstered the theory that dilute media were necessary for reproduction. The fact that a little oyster tissue was introduced into the cultures left in doubt the importance of the diluted medium. lt was not known whether or not the cells, during the short period of reproduction, depended for nutrient substance on the fluid thioglycollate medium, the oyster tissue, or stored nutrient in the D. marinum cells. The form of reproduction in these cultures was unexpected. Most cells reproduced by budding and fission into small loosely aggregated clumps of cells (Fig. 8A). Budding in oyster tissue had been observed rarely and was regarded as possibly atypical. In these cultures reproduction was mainly by budding and cleavage. Sorne advanced hypnospores apparently developed directly into sporangia containing numerous very small aplanospores, which were often liberated by rupture. Occasionally reproduction by means of the radially segmenting, morula-like bodies was observed as commonly seen in oyster tissue. In cultures of one-half the normal concentration of fluid thioglycollate medium the cells enlarged, but no reproduction occurred. In sorne of these enlarged cells, cytoplasmic F1c. 8. Reproduction of D. marinum in fluid thioglycollate medium diluted to l/50 strength. A. Fission and budding produces small loosely aggregated clumps of cells. B. Reproduction of D. marinum in sterile "sea-water" cultures. The grape-like clusters develop by fission and budding in early stages of culture. C. D. marinum in sea-water culture. Most of these "cells" are multinucleate, and in many cases the cleavage planes could be clearly seen. D. D. marinum in "sea·water" culture enlarged to show radial cleavage planes in sorne sporangia (?) . cleavage occurred, but did not continue beyond production of a few cells. No nuclei could be seen in these cells, but the original large eccentric nucleus was clearly seen. 1t is assumed that, if nuclei existed in the cytoplasmic segments, they were chromidial in origin. A second culture series which used only 1/ 40 strength dilutions of the fluid thioglycol­late medium, but was otherwise not different from the first series, was a failure. A third series incubated at lSºC also failed. A fourth series was held at 30ºC with dilutions ali at 1/ 40 strength with better results. Out of 22 cultures, four were judged to be good, with satisfactory reproduction of D. marinum. lt was noted that these were cultures which were not visibly contaminated by either yeasts, molds, or bacteria. Series four was unsatisfactory as a whole, adding little or nothing to the first series. The cultures which were successful ceased reproducing within 10 days after the cultures were set up. Attempts to subculture were without success. Apparently massive inoculation is pre· requisite to successful culture. Following these efforts, a numher of attempts to culture were made using oyster serum (sterilized by filtration), yeast extract, peptone, and fluid thioglycollate medium, in various comhinations and singly. All of these, including oyster serum, produced enlarge· ment of D. marinum cells. Reproduction failed to occur except, rarely, by budding and by cleavages. Culture with Fusarium. On November 2, 1954, a gaping oyster was minced with a Waring Blender, and the D. marinum cells were separated from the tissue by straining through severa! thicknesses of cheese cloth. Most D. marinum cells wash through such a strainer, while most tissue debris is eliminated. Cells thus recovered were added to vials of sterile seawater in which were placed excised bits of oyster mantle in an attempt to infect these tissues. After the mantle tissues were removed, the vials, containing large numbers of D. marinum cells in sterile seawater fortified with streptomycin and penicillin, were allowed to stand unmoved for a period of 15 days. On November 17, 1954, these vials were examined. Ali had developed a heavy mycelial mat found to be a species of Fusarium. A considerable part of the seawater had evaporated. Examination of the Fusarium showed that in all vials (14) masses of D. marinum had developed. No nutrient had been added to the seawater (sterilized by filtration). The homogenized oyster tissue and the dissolved suhstances in the seawater supplied the only nutrient available. Besides Fusarium, there were severa! other contaminating species of mycelial fungi, ciliates, and yeasts in sorne of the cultures. The D. marinum cells had reproduced via the radial cleavage route, as in the oyster, and the cultures when examined were made up mostly of sporangia or the aplanospores which carne from them. At the time of examination no oyster tissue could be found in the cultures, but most of the D. marirw,m cells appeared to he alive. Attempts to sub­culture from these seawater cultures failed. New cultures were set up on November 20, 1954, using sterile sea water fortified with antibiotics. As much oyster tissue as possible was strained out. Cells and sera were diluted to 1/ 200 with sterile seawater. Two and one half ce of this dilution was added to each of 20 penicillin bottles containing sterile seawater. Sorne of these cultures were inoculated with Fusarium spores from pure culture of the latter; others were inoculated with Fusarium mycelia from previous cultures, and severa! vials were inoculated with spores from a Candida culture. One set of vials was left without Fusarium or Candida. Each of these groups contained five cultures. At the end of one day, reproduction in sorne tubes had definitely begun. Six satis­factory cultures were achieved out of the 20 attempts. These six were still in good condition on December 9, 1954 (after 19 days). Ali cultures, irrespective of treatment, became dominated by Fusarium. Two of the cultures produced great masses of thousands of D. marinum cells and sporangia (Fig. 8C). At 19 days nearly all were multinucleate sporangia, as shown by stained smears. Nearly all reproduction was by radial cleavage (Fig. 2: J,K), but sorne budding and fission in early stages was observed. Sorne of these cultures produced giant sori of sporangia, the first of these seen (Fig. 9D). Sorne of these were up to 40 microns in diameter and had very thin walls. F1c. 9. Sori and aplanospores oí D. marinum in sea-water culture. A. A sorus containing severa! sporangia (?) ; B. Mature sorus containing aplanospores. C. Aplanospores from a sorus as in B. D. An early thin-walled "giant" sorus oí four multinucleate sporangia (3 shown in the photograph). E. Sori oí sporangia with thin walls. Each "cell" was multinucleale and was a sporangium. These giant sori appeared more or less consistently in cultures and often developed numerous sporangia. Studies to determine whether or not introduction of glycogen into cultures was helpful were carried out with negative results. Numerous cultures with graded amounts of glycogen added were less successful than were controls using only seawater. Nutrient agar failed to improve the culture methods. The final technique that gave the most consistent results was as follows: l. Culturing was done in 100 mm covered petri dishes to permit maximum aeration of a thin !ayer of sterile sea water on the bottom of the dishes. 2. D. marinum cells were introduced into the sterile seawater in small 3 to 5 mm· square pieces of heavily infected gill tissue. Cultures were made only from gaping oysters with strong ciliary action and without sign of bacteria! degeneration. 3. Gill tissues were washed in successive baths of sterile seawater to remove as many bacteria, fungus spores, flagellate and ciliate protozoa, and amoebae as possible from the gill net. 4. Every effort was made to control bacteria, apparently the cause of most culture failures. Penicillin and streptomycin were used in wash waters and cultures. 5. Each small block of gill tissue containing D. marinum cells was inoculated with spores of Fusarium from pure culture. Fusarium grew well in the still-living gill tissue, and its mycelia, in about a week's time, made a solid mat penetrating the tissues and subsisting on them. In a week to ten days the host tissues were absorbed. D. marinum cells continued development in the oyster tissue as long as it lasted. When the host tissues were gone, the D. marinum cells continued development in the mycelial mat, attached to the strands. lt is believed that the Fusarium produced an antibiotic protective against bacteria, and that it may also have produced sorne growth-promoting hormone effective on D. marinum. 6. Cleansing of glassware was done without detergents, and metal instruments were avoided. 7. Cultures were kept in a constant temperature box at 23ºC. In general, when D. marinum cells are free of host tissue, the first reproduction takes place by fission and budding, resulting in grape-like clusters of cells (Fig. 8B). Rever­sion to radial cleavage takes place early, and most subsequent reproduction duplicates the steps in the oyster tissue but with sorne differences. First, the cells in many cases secrete resistant walls, and second, the size of the mature sporangia is definitely ,much larger than those in oyster tissue. They may reach a diameter of more than 20 microns (Fig. 8D). Nuclear multiplication is always quite regular (2, 4, 8, 16 cells, etc.), and takes place without cytoplasmic cleavage up to the final divisions whkh separate the daughter cells. Cells resulting from such division immediately repeat the cycle, but not indefinitely. Apparently there is an end stage, which is an aplanospore (Fig. 9C). Sori developed in sorne cultures (Fig. 9: A,D,E). These produce aplanospores, which may develop to new sporangia prior to break-up of the old sporangial wall (Fig. 9A). Such sori may be up to 40 microns in diameter. Sorne of the sori are formed from enlarged uninucleate cells with very thin walls. The cleavage pattern of these is always identical to that of their smaller counterparts, but the result is a sorus containing many more aplanospores (Fig. 9B). The role of these giant sori is difficult to assess. lt is not known whether they represent responses to abnormal conditions, or whether they are normal themselves, and appear only under very favorable conditions. These large sori mature as a spore mass which looks much like similar structures in the Plasmodiophorales (as in Spongospora) (Fig. 9B). However, no flagellated zoo· spores have been observed to be liberated from these masses. It is possible that they are abnormal. Uniflagellate and biflagellate organisms commonly appeared in many cultures. Because their appearance was not consistent, it is believed that these, with one possible exception, were zooflagellates and not flagellated zoospores. The exception was a zoo­spore with single trailing flagellum which in severa! cultures attacked ciliate protozoa. In sorne cases the attacks produced chytrid epidemics which wiped out the ciliate popula­tions. The nature of these parasites is unknown, except that they obviously belong in the Chytridiales. It is believed that flagellated zoospores of D. marinum might attack any available cells in a culture. The presence of foreign chytrids in the crude cultures suggests at least the possibility that ali stages observed in the cultures may not have been D. marinum although most undoubtedly were. THE GENUS Dermocystidium PEREZ, D. marinum AND RELATED Low FUNGI Perez (1907) erected the genus Dermocystis and later (1908) amended it to Dermo­cystidium, because of pre-occupation. In 1913 he gave an extended description of the type species, D. pusula. It is unfortunate that D. pusula still is known only from the mature spore (hypnospore) stage with its large eccentric nucleus and vacuole with inclu­sion body. However, severa! other species of the genus have been described and from these a more complete picture of the genus is available. Ali species now placed in Dermo­cystidium (excepting D. marinum) are parasites of the skin, gills, or muscles of am­phibians and fishes. One of the unsolved problems is the relation of Dermocystidium marinum to the complex of species parasitic in vertebrales. A second problem is that of the taxonomic relationship of D. marinum within the lower Phycomycetes. These two problems are not as yet resolvable. That is not because of lack of information concerning D. marinum, but because (1) the Dermocystidium group parasitic in vertebrates is incompletely known, and (2) the large group of genera which, like D. marinum, belong vaguely near the lower Phycomycetes, are themselves known mostly from fragmentary accounts. The group of genera referred to, and discussed below, are taxonomic orphans in the sense that they are generally excluded from, or included only doubtfully in, known and accepted taxa. They have been shifted by various authors from the protozoa to the lower fungi or vice versa, or occupy a vague intermediate position on the border­line between the two groups. D. marinum and the complex of related species shown by Andrews (1955) and Ray (1954b) to exist in marine bivalve molluscs and annelids stand in the middle of these taxonomic orphans. The purpose of this section is to analyze the facts as known and define the problems remaining. Dermocystidium pusula Perez (1907) parasitizes the skin of Triton marmoratus and T. cristatus. Only the mature spore (prehypnospore?) stage is known. This stage occurs in small cysts in the skin. These cysts are undivided and appear to contain single thin­walled sporangia, and the "spores" are not infective. Each spore has a large eccentric nucleus, a basophilic cytoplasm containing chromidia, and a large "vacuole" contain­ing an inclusion of the general staining reaction of volutin. The pre-hypnospore stage of D. marinum is approximately identical to that of D. pusula, hence the placement in the genus Dermocystidium (Mackin, Owen and Collier, 1950). Other species placed in the genus Dermocystidium Perez by subsequent authors, and which parasitize fishes and amphibians, are nearly identical to D. pusula in the final spore stage, but species of this group vary much in details of development. Leger (1914) described Dermocystidium branchialis from the gills of Trutta fario. This author observed developmental stages in small cysts, 0.2 to 0.3 mm in diameter. These developing stages consisted of granular cytoplasm, like a plasmodium, containing scattered and very small nuclei. Scattered in the cytoplasmic mass were large inclusions which stained strongly with basic dyes. As the cysts developed, the cytoplasm of the multinucleate plasmodia broke up into islets, each with a single nucleus. These islets gave rise to the hypnospores. D. ranae Guyenot et Naville, 1922, which parasitizes the skin of Rana temporaria and R. esculenta develops through a granular plasmodial stage as does D. branchialis. The cysts of D. ranae are U-shaped rather than spherical or oval. The early plasmodium is "anucleate" when tested by the Feulgen method (Broz and Privara, 1952) but con­tained deep-staining granules ( of vol utin ?) when dyed with ordinary basic stains. D. vejdovskii Jirovec, 1939. parasitizes thc gills of the pike Esox lucius. Young cysts of this species also contain only granular plasmodium. In development this plasmodium first breaks into many nucleated sub-plasmodia. then these produce spores. This in­volves, therefore, the development of a sorus of sporangia rather than a single spo­rangium. and in this respect this species differs from the others. Davis (1947) described D. salrnonis from the gills of the salman (Oncorhynchus tshawytscha ) . This author failed to find plasmodia in the young cysts but did find immature cells of D. salmonis which were reproducing by binary fission. These cells differed from the mature spore stage by the Iack of a vacuole with inclusion, and many were binucleate. It seems possible that Davis failed to find the earliest stage, which may have been a plasmodium. Nevertheless the interpolation of a binary fission or budding stage in the developmental cycle is of great interest. The description by Reichenbach­Klinke (1950) of D. percae from the okin of the perch (Perca fluviatilis) failed to add new data on the life cycle. Hoshina and Sabara (1950) described D. koi from the skin and muscles of the carp ( Cyprinus carpio). These authors failed to find plasmodial stages, but their description adds an important detail to the life cycle. D. koi proliferates in muscle and skin of the host in to numerous polyp-like masses of cysts ( or sporangia) . These resemble very strongly the masses of sporangia characteristic of Rhinosporidium seeberi, parasitic in the nasal epithelium of humans and cattle. The proliferations of D. koi may result from auto-infection from an original single cyst. If this is so, then the hypnospores of this species are infective, at least under certain unknown conditions. An alternate theory is that the original infective cell, if not isolated by the host, may fragment, the parts then being distributed by phagocytes, each forming a new focus of infection. A characteristic of the cysts and polyps of D. koi is a meagre host response resulting in incomplete isolation of the thin-walled sporangia by the cyst wall. AII of the species of Dermocystidiurn are similar in that the hypnospore (1) de­velop'> a single large vacuole in the cytoplasrn which contains volutin bodies in various forms, (2) has a basophilic-staining reticular cytoplasm which contains nucleus-like chromidia, and ( 3) has a lar ge eccentric vesicular "resting" nucleus with a lar ge karysome. In ali cases the pre-hypnospore has a thin unsculptured wall. Vacuolated cells of the Dermocystidium type occur in other widely separated genera. For example, in the chytrids, such vacuolate hypnospores occur in Cladochytrium (Cladochytriaceae). They occur also in the Actinomyxidian, S phaeractinomyxon, and in Coelomycidium, commonly placed in the Haplosporidia. The hypnospore of the basic type found in D. pusula has characters found in widely separated species of Protozoa and Fungi. The best that can be said for the placement of D. marinum in the genus Dennocystidium Perez on the basis of the form of the vacuolated pre-hypnospore is that this character indicates that it could be a memher of the genus. The placement in the genus Dermocystidium of the various species parasitizing verte­brates has not been questioned. But all were relegated to the genus Dermocystidium on the basis of the similarity of the final spore form justas was D. marinum. As summarized above, sorne of these assumed species of Dermocystidium (D. salmonis, D. koi) differ much from others of the genus in developmental cycle. If D. marinum were separated from the genus Dermocystidium, there would be ample reason also to separate other species now included. If the form of the pre-hypnospore is not important, D. marinum appears to be related to such genera as Ichthyochytrium Plehn ( 1921) or to certain genera of the Haplosporidia orto Sporomyxa Leger 1908. AH of these have a basophilic cytop1asm containing chromidia, and ali develop by progressive cleavage to a sub­spherical sporangium-like body in which spore-like cells are produced_ There are about thirty of the more or less distantly related orphan genera mentioned above. The taxonomic status of these is in doubt and nearly all have been referred more or less positively to the "chytrids," to the Myxomycetes, or to the Haplosporidia. Occa­sionally the placement is narrowed and the groups generally mentioned as most nearly related are the Olpidiaceae and the Synchytriaceae. Three genera of these orphans are known to have flagellated zoospores and must belong to sorne chytrid group. These are (1) Blastulidium Perez, 1903, with a uniflagellated zoospore, (2) Blastulidiopsis Sigot, 1931, with a biflagellate zoospore, and Dermomycoides Granata, 1919, with a uniflagel­late zoospore_ Blastulidium, except for the zoospore, has little resemblance to most chytrid groups, but probably is near to the Synchytriaceae. Blastulidiopsis is basically like Blastulidium, except for the biflagellate zoospore. Following the mycologists' pre­cept that the number of flagellae is all-important and nothing else bears much weight, this organism most likely would belong to the Plasmodiophoraceae or the Lagenidiales. Dermomycoides occurs in cysts of the skin of Triton palmatus and these cysts are pre­cisely like those of Dermocystidium pusula Perez. However, the flagellated zoospores produced in the cyst are not in any detail like the hypnospores of Dermocystidium and the genus has been referred to the Olpidiaceae. The fact that other genera of the "orphan" group have not been shown to have flagellated zoospores does not mean that they may not have them. One is apt to overlook the effect of parasitization of animal rather than plant hosts. Most parasites of animal hosts have been fixed, sectioned and stained befare the parasites are found_ Their ap­ pearance when viewed alive is quite different from their appearance when stained. Haplosporidium when seen alive looks like a low fungus; stained it shows characters similar to those of sorne Microsporidia. The data indicate, however, that most of the genera of the "orphan" group have no flagellated zoospore, and thus must be excluded from the known taxa of low chytrids or the Plasmodiophoraceae. That leaves only the alternative of placing them in the Haplosporidian wasteba~ket, which now contains obvious fungus genera. It is believed that no good purpose is served by continued placement of doubtful genera in the order Haplosporidia. It only defers the time when the group of "orphan" genera are grouped together in a taxonomic unit and become one of the lower chytrid groups. At present it matters little that this group probably would not be a pure phylogenetic line with a single stem. It is generally admitted that most of the lower Phycomycete groups may be polyphyletic. Included in this group are: Blastocystis Alexeieff, 1911; Rhinosporidium Wernicke, 1903; Chytridiopsis Schneider, 1884; Chytridioides Tregouboff, 1913; Dermomycoides Granata, 1919; Lymphocystidium (Jirovec) , 1936; Ichthyochytrium Plehn, 1921; Mucophilus Plehn, 1921; H epatosphaera Gambier, 1924; Histocystidium Goodchild, 1953; Dermosporidium Carini, 1940; Mycetosporidium Leger and Hesse, 1905; lcthyosporidium Caullery and Mcsnil, 1905; Coelosporidium Mesnil and Marchoux, 1911; Sporomyxa Leger, 1908; Bertramia Caullery and Mesnil, 1899; Polycarium Stempell, 1903; Erythrocytonucleophaga lvanic, 1942; Blastulidium Perez, 1903; Endoblastidium Codreanu, 1931; Blastulidiopsis Sigot, 1931; and severa} others, includ­ing Dermocystidium Perez, 1908. Dermocystidium Perez seems to be most closely related to Dermosporidium Carini (1940). The only difference between these two genera is that the final spore stage in Dermosporidium has severa! vacuoles with inclusions and a central nucleus, while in Dermocystidium the final spore stage has one large vacuole and an eccentric nucleus. Dermocystidium is also closely related to Rhinosporidium. This latter genus produces spores which are quite similar to those of Dermosporidium. Elles (1941) relates Rhinosporidium to the Olpidiaceae, as do Chaudhuri, et al. (1945). Dermocystidium marinum fails to agree with the other species of the genus in that the number of spores produced within the sporangium is much smaller and there is no granular plasmodial stage. But the "plasmodial" stage has not been found in all the species assigned to Dermocystidium, notably D. salmonis Davis and D. koi Hoshiná and Sabara. D. marinum grown in seawater culture rarely develops a vacuole with inclusion body. According to the medium or host conditions under which D. marinum is grown, the form of the cell may be modified. Many immature D. marinum cells in the oyster host do not have a vacuole. The presence or absence of a "plasmodium" in sorne related genera (Chytridiopsis) seems to be dependent on unknown factors. Whether or not a "plasmodium" forms may merely be a matter of whether or not cytoplasmic cleavage parallels nuclear divisions. It seems best under the circumstances to leave D. marinum in the originally assigned place. Further study of the complex of species in marine molluscs and annelids which respond to the thioglycollate culture test may indicate that the marine forms should be removed from Dermocystidium Perez and either placed in a new genus or assigned to one or another of the genera listed above. There can be little doubt that D. marinum is a fungus. Strong evidence of its fungal nature is furnished by Ray's (1952a) demonstration that the hypnospore wall, after culturing in various media, will react with iodide to produce a deep blue color, and by his published photomicrographs showing tubular growths from the enlarged hypno­spores described above. Stein and Mackin (1957a) showed that the wall of D. marinum cells in oyster tissue stained deep red with the periodic acid-Schiff reaction, a charac· teristic of the cell wall of fungus cells. The cell wall of D. marinum was shown probably to contain hemicellulose also. Since mycelia are wholly lacking in the development of D. marinum either in the host oyster or in seawater culture, it must belong to either (1) the Olpidiaceae, (2) the Synchytriaceae, (3) the Plasmodiophorales, or an as yet un-named low group co· ordinate with the three named. The development of sori in culture strongly indicates a relation to the Synchytriaceae, but it is barred from that group by lack of a uniflagellate zoospore. lt is also obvious that D. marinum may be related to the Plasmodiophorales, from which it is also barred by lack of the biflagellate zoospore. There is thus no choice but to refer the genus Dermocystidium to Rhinosporidiaceae Ciferri, 1932. Ciferri called · attention to the close relationship of Rhinosporidium and Dermocystidium but placed the latter in the Olpidiaceae under the mistaken impression that its life cycle included a uniflagellate zoospore. Dermospüridium should then be placed in the same family, which would be co-ordinate with the Olpidiaceae and Synchytriaceae in the Chytridiales. How many more of the "orphan" genera should be included is problematical but many may qualify. If Dermocystidium is later shown to have a flagellated zoospore, the above placement would be unnecessary, and the genus would be included in Synchytriaceae as suggested by Mackin and Boswell, 1956. DISTRIBUTION OF D. marinum Distribution in Louisiana. Severa! hundred samples of oysters, from more than one hundred bays and bayous in the oyster-producing area of Louisiana, have been checked for infection by D. marinum. See appendix. Generally the distribution of D. marinum in Louisiana is almost the same as the distribution of the host oyster, with a few areas of continua! low salinity excepted. For further discussion of salinity effects see the section on epizootiology. Incidence in these samples has varied from zero to 100 percent, depending on the location of the sample, ecological conditions, seasons, and age of the oysters. The stations where zero incidence has occurred are all in areas marginal for oyster production because of mean salinity below 9 ppt or because of seasonal flushing with fresh water or by flooding of the Mississippi River. In Atchafalaya Bay, subject to continua! low salinity, D. marinum has never been found. In areas such as Sandy Point Bay, during periods of high salinity the incidence and weighted incidence may be high, while in periods of Mississppi River flooding the disease may disappear completely. Areas such as lower Barataria Bay are never free of disease, even in comparatively low salinity periods in winter. Sorne low incidences recorded in areas where the salinity is above 20 ppt were dueto sampling of immature oysters in new plantings. Data on distribution in Louisiana have been condensed as far as possible and are contained in an Appendix. Exact locations are not given in this appendix, but only the names of bays or bayous, and sometimes of more restricted areas within bays. An ex­planation of the appendix appears at its head. Range of D. marinum. The southernmost limit of distribution of D. marinum is not known. Of seven live oysters from near Tampico, Mexico, presented to the author by Mr. Albert Collier, five were found to be infected. This is the most southerly record now known. These oysters were collected in January of 1950, and sectioned by the author. lt is quite probable that the disease extends beyond Tampico. Oysters collected by Dr. S. H. Hopkins in 1951 from Fulton Beach, Aransas Bay, Texas, were found to be infected. Severa! lots of oysters from the same area were found to be negative. Ray ( 1954b) failed also to find D. marinum in that area, but found it in severa! samples from various parts of Galveston Bay. Hofstetter and Heffernan ( 1959) surveyed severa! Texas bays for Dermocystidium marinum infections. Aransas Bay and Galveston Bay were shown to have endemic areas of infection. The fungus was found on five out of six reefs studied in Galveston Bay, and on four out of seven in Aransas Bay. Sorne of the samples from Aransas Bay showed very heavy intensity of disease at times (Long reef, Jay Bird reef). These records indicate that the fungus may be on the increase in the Aransas Bay area. A few samples taken in Copano Bay, Lower Laguna Madre, and Matagorda Bay were negative for the fungus. Several samplcs of gapers from Mississippi, nrar Biloxi, have ali shown ·heavy D. marinum infections. Ray (1945b) also repor'ed a íS percent infection rate in oysters from the Biloxi area. Severa! samples from Mobile Bay have shown very heavy weighted incidence in severa! reefs in the lower western side of the hay. Ray (1954b) reported that D. marinum is common in the area around Pensacola, Florida, and Ingle and Dawson (1953) reported it from the Cedar Key area. Dawson (1955) found that oysters from numerous stations in Apalachicola Bay, Florida, had intensities of infection com· parable to those found in lower Barntaria Bay, Louisiana. From Cedar Key, Florida, south along the Florida península, there is no information on D. marinum although a few oysters are produced on the west coast as far south as Lee County. Similarly there are no records for the Atlantic coast side, nor are there any for the coast of Georgia. There are severa) records for the South Carolina coast from the Bears Bluff Laboratories. Oysters from the intertidal zones of Wadmalaw Island, South Carolina, seem to be largely free of D. marinum, but oysters in an experimental pond were found by the author to be heavily infected. D. marinum is common in North Carolina at Beaufort. The Virginia lnstitute of Marine Science has extensive records of D. marinum in the lower Chesapeake and its estuaries (Andrews and Hewatt, 1957). Most of the James River estuary seed beds are free of infections, probably because of the constant flushing movement of the water. The seaside bays in Virginia appear to be free of infection. Oysters in the Virginia seaside are intertidal and are subject to very low temperatures throughout much of the winter, which probably accounts for the absence of D. marinum. Dunnington (1956) reported that D. marinum was found on both sides of the Maryland Chesapeake from about the Patuxent River southward to the Virginia line. Anonymous (1958 J report referred to records of D. marinum in Delaware Bay dating to 1953. In Delaware Bay the parasite was somewhat spotty in distribution, the infected areas mostly centering around heavy plantings of Virginia seed. So far as now known, the Delaware Bay area is the northernmost limit of distribution of D. marinum. Severe winters seem to be the limiting factor in defining the northward range. However, little effort has been made to determine whether or not D. marinum extends to more northerly areas. EFFECT OF D. marinum ON THE HosT ÜYSTER, EXPERIMENTAL INFECTION Histopathology of infection. Fungus disease of oysters was first noted because in many cases the oyster meats shrank excessively with heavy infections. Such shrinkage was not confined to gapers, nor were all oysters heavily infected with D. marinum shrunken in appearance. Those oysters which had well developed gonads just prior to spawning usually showed no obvious shrinkage. Oysters dying in late summer usually were more or less shrunken, and a slightly yellowish cast to the meats was usual. Fig. 10 shows an excessively shrunken oyster, heavily infected with the fungus. Maceration of the adductor muscle, as shown in this specimen, is sometimes apparent on gross examina· tion, and pus pockets of leucocytic cells are often seen also. Extremely "glassy" or transparent oysters usually are not infected by· D. marinum. These oysters are diseased but the cause of "glassy" oysters has not been determined. F1G. 10. An oyster recently dead of D. marinum infection. Note the shrunken meat. Mackin (19Slb) and Mackin and Wray (1952) studied the effect of heavy infections of D. marinum on the tissues of the host oyster, using oysters in advanced disease for making sections for comparison with sections of normal oysters. The results are sum­marized as follows: (1) Light infections have little cffect on the host oyster. D. marinum cells in lightly infected oysters usually are hypnospores, and few reproductive stages are found. Light infections may be carried for extended periods without proliferation, especially in winter. Light infections usually are found in the gut epithelium. (2) Heavy infections cause gross destruction of tissues of the host. Ali types of tissue are invaded. The Leidig cell tissue (Fig. 4A) often contains masses of parasites and may be destroyed over considerable parts of the body. Arterial walls and heart are also susceptible to heavy invasion (Fig. llA). Destruction of gut epithelium (Fig. llB) and adductor muscle (Fig. llC) is commonly found. Ganglia and nerves may be at­tacked. Abscessed areas of the mantle and palp are characteristic of heavy infections ffig. llD). Renal epithelium appears to be the least affected tissue. ( 3) Abnormal deposits of cero id ( see discussion below) which causes the yellowish cast to oysters in advanced disease is characteristic of acute infections. ( 4) There is no indication that D. marinum cells produce exotoxins in any significant amount. The appearance of sections indicates that damage to the host is due almost entirely to lysis of tissues. In sorne advanced cases, there may be more cells of the parasite than of the host. Hewatt (1952) noted that infection with D. marinum arre~ted shell growth or caused loss of shell weight from one to eight or ten weeks before death of the oyster from fungus disease. He made weekly weighings of individual oysters under water over a six-month period. Hewatt was able to predict deaths from the diminished growth or loss in shell F1G. 11. Sections through tissues of diseased oyster. A. Mantle artery showing masses of D. marinum cells in the lumen and surrounding vessel wall which has greatly hypertrophied. B. Numerous D. marinum cells in the gut epithelium. Lumen of the gut is at the bottom of the photograph. C. D. marinum in the adductor muscle. D. Abscessed area under mantle epithelium. weight. He observed also that sick oysters failed to open the shell and feed in most cases, and assumed that the closed oysters resorbed shell material in advanced stages of disease. Menzel and Hopkins ( 1955a, 1955b) studied the relation of shell growth and increase in weight of oysters to parasitization by D. marinum. Shell growth and weight of individually marked oysters were measured over a two-year period at Bay Ste. Elaine, Louisiana. D. marinum infection first slowed growth, then caused it to cease altogether. Their data indicate that the effect of fungus infection may begin eight to eleven months prior to death from fungus disease. lnfections acquired in one summer failed to produce death of the host until the following summer. Ray, Mackin, and Boswell ( 1953) studied the effect of heavy infections in excised bits of gill tissue. Small pieces of living, heavily infected gill tissue were excised and placed in sterile seawater in Carrel flasks. Antibiotics were used to control bacteria! contamina· tion. Control (uninfected) tissues were observed simultaneously. Photographic records were made over the period necessary for destruction of the gill tissues by the fungus, which was about two weeks. This study has been repeated severa! times. Destruction of the host tissue occurred in ali cases. In the same report (Ray, Mackin, and Boswell, 1953; Reíd, 1953) , the effect of fungus infections of different intensity on meat weight of oysters, as compared with weights of uninfected oysters, was studied. The normal relation between meat weights of oysters and shell capacity was established for different seasons. Moderate and heavy infections with fungus disease caused significant decrease in meat weight, independent of season. Light infections did not produce significant decreases in meat weights . . Stein and Mackin (1957a) used histochemical methods to determine the effect of D. marinum infection on glycogen content of oysters. Sections were made of oysters in advanced stages of disease and compared with similar sections of uninfected or lightly infected oysters. The periodic acid-Schiff (PAS) technique was used for staining as described by Lillie (1954). Malt diastase was used as a test for specificity, since PAS will stain substances in oyster tissue other than glycogen. This study showed that glycogen depletion occurred in heavily infected oysters, but that the effect did not arise from direct selective utilization of glycogen by the parasite. The effect was due to destruction of Leidig cell tissue in which is stored most of the glycogen, and replacement of this tissue by fibrous tissue and masses of leucocytes. Stein and Mackin (1955) also studied the production of ceroid (ljpofuscin, chromo­lipoid) in diseased oysters. lt had been noted (Mackin, 195lb) that the so-called "pigment cells" appeared to increase in oysters in advanced stages of fungus disease. He supposed that the pigment cells contained hemosiderinoid. To test the hypothesis that increase in the ceroid was associated with heavy infections of D. marinum in oysters, counts were made of pigment cells in randomly selected tissue areas around the gut in stained sections of heavily infected, lightly infected, and unin­fected oysters. Counts were made in ten oysters of each class and in ten randomly selected fields in each oyster. The mean number per field in heavily infected oysters was 14.59, and in the lightly infected and negative oysters it was 8.30, a statistically significant difference. The presence of excess ceroid indicates an imbalance in fat metabolism, possibly due to an increase in oxidative and reductive metabolic processes as a result of disease. Ceroid is known to develop in unusual amounts in certain diseases, in sorne manner connected with defensive host reactions. Macoma balthica appears to have a high degree of resistance to infection. Cells of Dermocystidium sp. in that host degenerate in cyst-like cavities amid increasing amounts of ceroid. Much of the cernid seen in sections of oyster tissue may result from degeneration of dead D. marinum cells. W eighted lncidence of Fungus Disease in Gapers and in Live Oysters. Studies compar­ing intensity of disease in dying oysters with the intensity of disease in survivors have been made at severa! field stations. Where lysis of tissue rather than exotoxin is re­sponsible for the main damage to the host, it may be assumed that oysters dying have measurably heavier infections than survivors. A numerical system for estimating the intensity of infections in oysters has been widely used (Mackin, 1952a ; Ray, 1954a, 1954b ; Andrews and Hewatt, 1957). At present the different numerical grades of infection are defined as follows: 5. A heavy infection is one in which the fungus cells are concentrated in great num­bers in ali tissues. Thioglycollate-cultured tissues appear macroscopically greenish-blue to black in color when iodine solution is applied. 4. Moderate to heavy infections are those that appear to be intermediate between the moderately heavy infections and those that are obviously heavy. 3. A moderate infection is one in which the tissues are heavily infi!trated in sorne areas, but lightly dispersed in others. 2. A light to moderate infection is intermediate between a light infection and a moderate infection. l. A light infection is one in which the fungus cells number between 10 and 100 in a preparation. Generally speaking small local concentrations of numerous cells are not considered as light infections. 0.5 When fungus cells in one preparation number less than 10 in an entire prepara­tion it is classified as very light. Usually a search is necessary to find the few fungus cells present. O. No infection. Many studies suggest that sorne oysters probably die of D. marinum infection when the infection intensity is only moderate. Because moderate infections are those in which there are local areas of heavy infection, it is assumed that chance, early, acute attacks on vulnerable organs cause these dcaths. Under the weighted system described above, 5.00 is the highest possible score, occur­ ring only rarely where all oysters of a sample are heavily infected. A population of live oysters with a weighted inciriod was May 6 to 9, 1953, and the weather was warm. Ali procedures were the same as in the first experiment except a close check was kept on the order of gaping. The experimental oysters gaped much more rapidly in the second study than they did in the first, probably because of the higher air temperature and the slightly higher original intensity of disease in the experimental oysters. The data indicate that the treatment produced acce!era~ ion of disease in the oyster populations used. They also show that oysters with heavy infections gape earlier, and have less resistance to holding out of water than do those with lesser infections. In the first study. the pre-experimental sample showed that about one in 25 oysters of the experimental population was heavily infected. There were about 10 heavily infected in the p'.)pulation of 250, and 11 heavily infected oysters gaped when the 250 were held out of water. The control sample taken from the non-gapers indicated that there were no heavily infected oysters remaining in this group. Ciliary Activity in Diseased and Non-diseased Oysters. Obserrntions of diseased oysters indicated that in late stages of disease, feeding rates were reduced. Sections usually showed that the gut of most heayily infected oysters was empty. Studies by Hewatt (1952) indicated that oysters in adrnnced stages of fungus disease kept the shell closed most of the time and therefore were probably feeding less than oysters with light disease or no disease. It was decided to test the efficiency of ciliary action of the gills, as an indicator of reduced respiratory and feeding efficiency. Lund (1949, 1957) compared the ciliary capacity of diseased oysters for production of faecal and pseudofaecal matter with that of normal oysters. He used oysters shipped to him from Barataria Bay by the writer and these oysters probably included sorne with fungus disease. However, the oysters were mostly young ones and it is probable that TABLF. }.1 Comparison of weighted incidence of fungus diseasc of gapers and sun·irnrs when held out of water. Experiments 1 and 2 used different populations of oysters 1¡..t>ighted incidenc:e of populalion Exp. no. Air temp. range. ºC :\o. oysters in experimental population Pre­experimenl In gapers from the experiment In no n-gape rs (control) --­---­ 1 2 15 to 25 18 to 27 250 435 1.66 1.70 3.20 2.69 1.72 2.20 Lund was dealing also with sorne disease in addition to DermOC)'stidium. Only those which were Yisually diseased in advanced stage by the end of the study were placed in the diseased group. HP compared these with another group (controls) which may ha Ye included oysters lightly infected with various diseases as well as sorne which were actually "healthy". Lund's study probably providt>d the first experimental assessment of a disea'e on a commt>rcially valuable invertebrate, in terms of physiological derange­ment. The prt>sent study corroborated Lund's finding and by careful diagnosis measured the efft>et of one specific disease as follows. The expt>rimental tank devist>d by Lund (1949, 1957) was used in these studies. By Lund's method. the ciliary activity of control anrl experimt>ntal oysters is measured by means of a lucite trough which collects tht> faecal and pseudofaecal matter precipitated by a series of oysters. The trough was diYided into three smaller troughs, running lengthwise, and each of these three was divided into six compartments in linear series. Each compartment was designed to contain six small oysters. However, oysters as small as those used by Lund have only light infections of fungus disease. It was necessary in this study to use oysters of larger size, and onl y three of these larger oysters could be placed in each compartment. In one of the three troughs we placed only shells of oysters. in order to measure the amount of silt precipitated without the action of oyster gills and mantles. The control trough and the experimental trough each con­tained 18 oysters. Each experimental oyster was matched for size by a control, and the two of each matched pair were placed in the same relative position in their respective troughs. Sizes ranged between 21;2 and 3% inches in length. The experimental oysters for the first study were taken on April 9, 1952, from a planted bed at Philo Brice light in Lake Raccourci. A check of a sample of thirty oy~ters by the thioglycollate method showed that approximately 67 percent of the experimental oysters were infected, and that the weighted incidence was 1.60. The experimental oysters were kept in trays or racks under the Iaboratory until the beginning of the study on April 26, 1952. They were planted in September of 1951, and thus were probably about 20 months old. The control oysters were brought from the Chene Fleur station April 25, 1952, and were kept for the intervening two days in a running water aquarium in the laboratory. These oysters were from a group which set in May of 1951, and thus were approximately 12 months old. Although younger, they were about the same size as the experimental oysters. A sample of 25 of these oysters was examined; none were infected. Twenty-five additional oysters were examined a few weeks later and again were ali negative. Oysters and shells were carefully cleaned of ali adhering silt before placing them in the trough with running sea water. Water was fed into the three troughs in equal measured amounts from a single constant-head tank, each trough receiving a flow of 1000 ce per minute. The actual amount of turbid materials suspended in the water varied during the ten days of the study, but was the same within narrow limits in alJ three troughs at any one time. Turbidities in the experimental troughs were often high, but were never as high as they were in Barataria Bay at the same time under natural con­ditions. The heavier silt particles settled out in the seawater cistern and constant-head tank before reaching the experimental troughs. On May 5, 1952, the water flow was shut off, and the oysters and shells were removed from the trough after being carefully cleaned in the water in their respective compart­ments. The pseudofaecal and faecal matter were allowed to settle, were removed from each compartment, and were transferred to graduales for measurement. The graduates were set aside for 24 hours to allow the materials to settle before reading the amount. Silt from the trough containing the shells was similarly collected and measured. The amount of settling out in the compartments containing shells was subtracted from the amount in corresponding compartments containing oysters. The difference in the amount of silt from each oyster compartment and the amount precipitated in the corresponding shell compartment is the amount of faecal and pseudofaecal matter produced by the oysters in that compartment. TABLE 15 Amounts of faecal and pseudofaecal matter in ce produced by control (uninfected) and experimental (mostly infected) oysters Compartment 6 Total Control oysters 106 178 198 205 214 107 1008 Experimental oysters 166 130 112 23 154 29 614 The data resulting from this study are presented in Table 15. The control oysters produced 64 percent more faecal and pseudofaecal matter than did the infected group. In all compartments excepting the first the control oysters exceeded the experimental oysters in ciliary activity. Since sorne of the silt was removed by the oysters in each compartment, the amount decreased successively in each compartment through the trough. However, the efficiency of the oysters in removing the materials apparently increased with the decrease of the amount of suspended silt, for the amount precipitated by ciliary action increased through the first five compartments. Apparently the small amount of silt remaining became a limiting factor when the sixth compartment was reached, for only half as much was precipitated as was the case in compartment 5. The pattern of precipitation of silt for the experimental oysters was rather irregular. Oysters of compartment number 1 produced the greatest amount, those of compartment number 5 the next largest, and number 4 the least. Thus it is probable that in compart· ments 1 and 5 ( which compare favorably with the controls) uninfected oysters were placed, while in compartments 4 and 6 (in which deposits were negligible) one or more oysters in advanced stages of disease were placed. No experimental compartment attained the average amount produced by the controls. In the case of the experimental oysters, the erratic variations in amount of faecal and pseudofaecal material produced in the different compartments probably represented variations in disease intensity. According to the sample checked for incidence of the population, one·third were not infected, and another third were lightly infected. The second study testing the effect of D. marinum infection on ciliary action in oysters was set up on August 4, 1953, again using the Lund tank, and terminated August 20, 1953. Oysters were raised from spat at the Chene Fleur field station. At the time this study began they were just over two years old. Thirty-eight oysters were selected for approximately uniform size and weighed. They were then matched in pairs of nearly equal weight. One of each pair was used for an "experimental" oyster, and the other was used as a "control". There were 22 pairs thus matched for equal or nearly equal weights. Eighteen pairs were used to initiate the experiment and four pairs were held in reserve as replacements for oysters dying during the study. The number of replace­ments required was underestimated and replacements could not be made for ali oysters that died. Sorne "control" oysters developed heavy infections and thus became "experi­mental" oysters. The oysters in the experimental aquarium were arranged in the order of their weights from the seawater entry end to the exit end of the aquarium. Pseudofaecal and faecal matter was collected and measured for volume. The combined pseudofaecal and faecal matter reflects the ciliary activity of the oysters, and the faecal matter is a measure of the amount of food material actually ingested by the oyster, minus that part digested. Prior to the starting date of this experiment a sample of 25 oysters from the Chene Fleur group used in this study was analyzed by the thioglycollate method for degree of infection by Dermocystidium marinum. The weighted incidence of infection of the sample oysters was 0.48, and 40 percent were found to be infected. There were no heavily infected oysters in the sample. Ali experimental oysters were infected with Dermocystidium by the "injection" method. Studies described in earlier sections of this report show that this method pro­duces nearly 100 percent infection in one day's time and that multiple infections prob­ably take place, resulting in rapid development of disease to an acute stage. Results of this experiment confirm the efficiency of the infection method used. Since a certain number of experimental oysters were previously infected, the infection by the injection method was superimposed on a previous infection in sorne of the experimental oysters. lt was also added to by natural infection from the aquarium water supply in the course of the experiment. The "control" oysters in this study were injected with tissue mince of uninfected gapers. These gapers were oysters from Redfish Bay, Louisiana, which died of culling injuries. Three meats of these oysters were broken up in a W aring Blendor, and after dilution with sterile seawater the tissue mince was injected through small holes in the shell into the shell cavity. The control group provided oysters negative for disease, sorne in light stages of infection. The disease developed more rapidly in the experimental oysters than was expected and in the 25 days of the experiment, 9 died with heavy infections. Among the controls three died of causes other than Dermocystidium disease and three died with heavy infections of D. marinum. Sorne light natural infections must have developed very rapidly in the controls. When an oyster died in the experimental or control tank it was replaced as long as reserve replacements were available. If the gaper was in the experimental tank, its matched mate in the control was also removed, and vice versa. Only eight oysters re­mained in each of the control and experimental troughs at the end of the study. All survivors were checked on the closing date for intensity of infection. The oysters were then grouped according to the intensity of infection and the amount of pseudofaecal and faecal matter produced by each oyster was calculated on a per day basis. A check was made of the water flow through the three troughs. Water level was held constant in an overhead tank by an overflow tube. The glass tubing through which water was fed into the experimental troughs was calibrated for equal diameter in ali three. They were equal within very narrow limits and were cleaned daily. The flow was at the rate of one liter per 51 seconds plus or minus one second. Fluctuations were caused by slight fouling of the tubes and varied in the same direction in the three tubes. The flow was timed with a stop watch. The results of this study are summarized in Table 16. TABLE 16 Amounts of pseudofaecal and faecal matter produced by oysters with different intensities of infection with D. marinum (Exp. 1) Pseudo- Total Faecal matter faecal matter production - lntensity oí infection --·-­ No. oyste rs tested Total no. oyster-days o[ testing per oysler per day (ce) per oyster per day (ce) per oyster pe< day (ce) Heavy 8 71 0.48 0.70 1.18 J\foderate 6 90 0.62 0.77 1.39 Light 6 72 0.91 l.28 2.19 Very light 4 43 l.01 1.80 2.81 NegatiYe 6 58 1.11 1.70 2.81 The total of pseudofaecal and faecal matter reflected ciliary activity and was indirectly a measure of respiratory activity but probably did not represent, with any great degree of accuracy, the feeding activity of the oysters. Feeding was better represented by the faecal matter production alone. Generally the data in Table 16 plotted as Fig. 17 show infection corresponding inversely with total pseudofaecal and faecal production. The very light and negative classes were combined for this calculation since these two had identical records as shown in Table 16. The third experiment of this series was set up on August 14, 1953, and the study was terminated at the end of a 21 day period. The oysters used in feeding experiment no. 3 were obtained from Milford, Connecticut, through the courtesy of Dr. Víctor Loosanoff, Director of the Milford Biological Laboratory of the U. S. Fish and Wildlife Service, and Mr. Joseph Uzmann, guest researcher at that laboratory. A considerable sample of these oysters was checked by the thioglycollate method to determine whether there were any infected ones among them. No infected oysters were found. Experimental oysters were infected with Dermocystidium by the injection method, the injections taking place on August 13, 1953. Ali oysters were weighed and matched in triplets; one of each three was a control and the other two were used in experimental groups A and B. Each of the two experimental groups contained nine oysters and the control group contained nine oysters. The data show that the injection method was successful in producing immediate infection in ali experimental oysters. Control oysters picked up a considerable natural infection from the water flow (Table 17) ; but no control oyster reached a stage of heavy infection in the period of the study, and none died. On the other hand 67.0 percent o Q \iH" T" '• F1c. 17. Effect of intensity of disease on ciliary activity as shown by production of faeces ami pseudofaeces. For deta ils of experimentation see text. TABLE 17 Production of pseudofaecal and faecal matter by oysters with different intensities of disease Period: August 14, 1953 to September 4, 1953 (21 days) Pseudofaecal and Wei¡?:hted incidcnce :'\o. faccal matter per of disease oysters used oysters per da~· (ce) Experimental Group A 4.77 9 145 1.95 Experimental Group B 5.00 9 152 1.93 Controls 2.78 9 189 2.68 of the experimental oysters (both groups) died prior to the end of the study (21 days) , and on the following day two more died, making a total of 78 percent. Excepting as noted, the third experiment followed the procedures for experiments 1 and 2 and received the same water flow. Oysters of the third experiment were concen· trated in the three compartments of the upper end of the Lund trough. Ali three divisions were used, the controls in the right side, experiment A in the middle and experiment B on the left. In assessing the study the following points should be kept in mind. (1) Ali oysters started out with equal infection. (2) Experimental oysters received a massive initial infection by injection of infectivc elements ir.ta the mantle cavity. and were ali infected on the first day. This infection was added to by natural infection from the water stream. (3) The infection intensity increased rapidly in the experimental oysters, ranging probably from light to moderate in the first week, from moderate to moderately heavy or heavy in the second week, and attaining a heavy leve] in ali oysters by the end of the third week. Because of progressive development of intensity from zero to heavy, faecal and pseudofaecal production were predicted to decline from week to week. ( 4) Control oysters also, with one exception, became infected from the natural water stream. (5) Leve! of infection in the control group was never as high as in the experimental group, but more than half had attained a leve] of acule disease (but not heavy) by the end of the third week. (6) With progressive development of disease in the control oysters decreased faecal and pseudofaecal matter were predicted by the end of the third week. (7) The decrease predicted was less than in the experimental oysters, because of the differences in initial leve Is oÍ infection. Table 17 contains the data derived from the third experiment on production of faecal and pseudofaecal matter. Experimental groups A and B produced nearly equal quantities of pseudofaecal and faecal matter, much below the level of the controls. Assuming that the controls represent 100 percent, the two experimental groups produced only approxi· mately 71 percent. These data are also presented graphically in Fig. 18. In computing the values on a weekly basis, ali oysters producing for a part or ali of each week were included in the calculations. In the case of those producing for only a part of the week. the production figures were increased proportionately to represent a fu]] week. As shown by the graph, ciliary and feeding action were not only considerably less in the experimental oysters, but decreased progressively for the three weeks of the study as infection intensity increased. The controls showed a different pattern. Ciliary activity and feeding increased in the second week over the first. probably due to acclimatization to the aquarium conditions. In the third week there was a drastic slowing down of ciliary action as the acule disease stage was reached in sorne control oysters. EPIZOOTIOLOGY2 Mackin, Owen, and Collier (1950) first mentioned the relation of temperature and salinity to incidence of Dermocystidium in oyster population. Since that time numerous studies have been reported bearing on the development of epizootics caused by D. marinum. Mackin and Wray (1952) outlined the basic factors affecting development of epizootics and further discussed the role of physical and chemical factors. Ray (1953a) studied the relation of age of oysters and incidence and intensity of infection. Ray (1954b) and Ray and Chandler (1955) reviewed the data on salinity and temper­ature as factors in epizootiology and presented experimental data. Owen ( 1955) con­ducted considerable experimentation on the effect of low temperatures and low salinity on infection rates, and discussed the relation of field mortality rates and salinity, as well as seasonal variation in incidence. Mackin ( 1956) presented data on salinity tolerances of oysters and D. marinum, Andrews and Hewatt (1957) discussed epizooti­ology of the parasite and Andrews (1957) studied the effect of density of oyster popu­lations and infection incidence and intensity. Mackin and Sparks (1962) presented data on the development and structure of epizootics on experimental tray populations. AH of these authors have presented information in miscellaneous other studies which deal with the problems of epizootiology. These studies will be summarized here. Composition of Oyster Populations as Related to Disease-definitions. Recognizable at present, the types of individuals in oyster populations are as follows: a. Susceptibles are those individuals which may contract fungus disease. Degree of susceptibility may vary more or less from individual to individual, and from race to race. lt may also vary seasonally in any one individual and possibly may vary with other environmental conditions, or with age of the oyster. b. lmmunes are those possessing a capacity to resist infection or development of disease if infected. An immune individual may be a "carrier" if infected but resistant to development of disease. The existence of such individuals, so far as D. marinum is concerned, has not been established. lmmunity may be acquired or "natural", the latter implying hereditary capacity for coping with disease. A susceptible ( or immune carrier) which has contracted disease is referred to as a "case". There is no way of distinguishing between cases which are infected susceptibles and immune carriers, if the latter exist. The use of the word "case" does not here imply that the oyster is significantly diseased but only that it is infected as shown by the thioglycollate culture diagnosis method. As considered here, the word "epizootiology" includes consideration of enzootic periods as well as epizootics proper. lt considers the effect of disease on populations of oysters but does not exclude examination of data applicable to individuals. What applies to individuals and what applies to populations may be inextricably interdependent. At present it has not been demonstrated that there are races or strains of D. marinum differing in virulence. Although these may sorne day be proved to exist, it is assumed meanwhile that virulence in D. marinum varíes with environmental factors but that only one genetic race exists. Epizootics on Oyster Beds. Studies of mortalities due to D. marinum on oyster beds are too incomplete for analysis. lt is inferred that because weighted incidences of disease 2 Epidemiology of an animal population. INTENSITY rlf INFECT ION Frc. 18. A. Effect of infection with D. marinum on production of faecal and pseudofaecal matter. Experimental oysters were infected by the injection method; controls were uninfected at the begin­ning of the study, but sorne became infected from the sea water supply before the study ended. Note the difference in scale of the three graphs. B. Same experiment as shown in ISA, but the oysters were sorted according to intensity of infection as determined at the end of the study. in oyster populations of planted beds and natural oyster reefs reach figures comparable to those in experimental populations with high mortality rates that similar mortalities occur on the planted beds and reefs. Experimental populations in aquaria with infec­tions equal to those in oyster heds are thought to have generally higher mortalities. Tray-held populations, on the other hand, are better off than most bottom plantings so far as environmental factors are concerned, and should undergo losses to disease com­parable to those in populations of bottom plantings. This belief is strengthened by many observations in the field. Ordinarily, investigations of reported mortalities are too late for extensive study; the bed is usually found decimated, with large amounts of shell, boxes (hinged shells), and a small number of survivors. The best that can be done under such circumstances is to sample the survivors for intensity of disease. However, there have been a few experimental studies of mortality in planted beds. St. Amant et al. (1958) presented figures on mortalities in experimental bottom plantings. Oysters were planted in November, 1955, when 8 to 12 months old. Approxi­mately 13 months later (Dec. 7, 1956) 82.5 percent were dead. They showed that 50 percent of these died in the summer of 1956 (May to October). They termed these excessive losses "summer mortality" which losses they said "are attributed to the effects of a fungus infection, Dermocystidium marinum". Cumulative mortalities as recorded by St. Amant, et al., are presented in Fig. 19. The method of estimation of mortality was not stated, but it is assumed that it was based on use of "boxes". This method is always in error and the actual mortalities are always higher than indicated by the box count method. Menzel and Hopkins (1952) similarly recorded mortalities in an experimental bottom planting. Their data are as complete as they could be made for bottom plantings. The planting was at Bayou Bas Bleu, where conchs were present only in small numbers. Stone crabs contributed to the mortality along with fungus disease. The authors believed that destruction by stone crabs was higher than could actually be accounted for because of fragmentation of the shells by the crabs and consequent loss of the "evidence". They believed also that D. marinum was a major cause of mortality. Mortality in 15 months was calculated to be 75 percent, most of which occurred in summer months with the highest death rates occurring in September and the lowest in January and February. Plantings were also made by Menzel and Hopkins in an area of higher salinity (Bay Ste. Elaine) where conchs played a greater role in destruction of oysters. Fig. 20 shows the form of the mortality curve at this station. There seems to be little difference between the Bayou Bas Bleu and the Bay Ste. Elaine mortality patterns. Both had least mortality in mid-winter and high peaks in the summer after a gradual rise through the spring. Epizootics in Tray Populations. As indicated above, the bottom planting curves 'ºº I MQfil~L,l_T~~-TO FUNGUS ~ 90 > ~ ªº § 70 ~ 60 r WQIH A. TY-­ VUE TO CGNCHS------, r > ¡;:. 50 ~ 40 30 'º '-->"--~~~~~~~~~~~~~~~~·~--~ '.IOV O~:: JAr. ~[9 MAR APR MAY ..UNE JULY AUG SEPl OCT NOV DEC 195!> 1956 MONTHS F1G. 19. Mortality of oysters in a bottom planting in Louisiana. Data from St. Amant et al. (1958). Mortalities were determined by sampling. Total mortality in a 14 month period was 82.5 percent. .1 N ~ J F M A M J ASOND J 1947 1948 19 4 9 Frc. 20. Mortality of oysters in a bottom planting in Bayou Bas Bleu, Louisiana. Data from Menzel and Hopkins (1952). An undetermined number of the mortalities were due to predators, especially stone crabs (Menippe mercenaria) . The graph shows a summer peak usually indicative of heavy D. marinum mortality. exhibited herein do not show exact epizootic curves for Dermocystidium disease, be­cause predators (and possibly other diseases) were not separable from the fungus disease as a cause of mortality. Experimental populations of oysters held in trays provide much more information because data on incidence and intensity of disease may be obtained along with exact mortality rates. Predators can be largely eliminated as mor­tality producers by caging the oysters, and morbidity data as well as mortality data from fungus disease are available from periodic samplings. In those areas easily acces­sible, so that examinations can be made daily or weekly, dying oysters may be recovered in sufficient percentage to make relatively certain what part of the total deaths are due to disease and what part to other causes. Lastly, experimental populations held in trays may be selected for intensity of disease when experimentation begins, and data on rate of infection of uninfected populations may then be obtained. Andrews and Hewatt ( 1957) measured the impact of fungus disease on oysters held in trays in the York River estuary in Virginia. Oysters from areas free of the disease (James River seed grounds) were moved to an area where the disease is enzootic. Epi­zootics resulting were measured in the summer of 1953 and the same population was observed through the winter and to the end of 1954. These 800 oysters were "planted" in April of 1953 but remained free of disease until August when mortality from fungus disease began. A small epizootic resulted and reached a peak in death rates in September. About 9 percent of the population died during August, September, October, and Novem­ber. The records show that more than half the population became infected, but the infection peak was reached in late October or early November. By the following March, 1954, the disease had disappeared from the population (had dropped to such a low ebb that the standard culture method of diagnosis failed to reveal its presence). Infections in the second year appeared in June, two months earlier than in the previous year. A massive epizootic developed during the summer, resulting in loss of about 64 percenf of the remaining population. The peak of this epizootic was August and September, and deaths had ceased to occur by December. Fig. 21 shows the trend of epizootic develop­ .000 0,900 O.BOO O.TOO 0.600 o.500 Q,400 0,300 0.'00 •---• CASE l'IATE / /''\ OEATH RAT( TO O MAR't\J\\ / ' > i//I \ ' 0.200.? a so e ¡ 1\\ \ 0.100:; / ' ' 'I ~ · I / \ • / I ~ \ / ' \ J1J /:;~ ' / ¡ J S O N 0 J ' "' 1954 Frc. 21. Case rates and death rates over a two-year period in oysters held in trays in the York River. Data are from Andrews and Hewatt (1957). Oysters were free of disease at the beginning of the study. Although more than one-half of the oysters became infected in the first summer, heavy mortality from disease did not occur until the second summer. ment in this tray population. Case rates, total death rates, and rates of death due to D. marinum are shown. The lag in elimination of infections after all deaths had ceased is particularly well illustrated in these graphs. Also, in the epizootic of 1953, fungus disease accounted for only about 60 percent of all deaths, while in 1954 fungus disease accounted for 95 percent of all deaths. During the peak of the 1954 epizootic, there were hardly any deaths due to other causes, and by October 96 percent of the population was infected. It is interesting that small mortalities developed in February and May of 1954 which probably indicated the presence of a minor disease other than the dominant fungus disease. Another tray population studied by Andrews and Hewatt showed a similar epizootic development (Fig. 22). Earliest infections occurred in April (not shown in the graph). In May a scattering of deaths occurred and the epizootic reached its peak in September. Fifty-two percent of the population died of fungus disease in the period from May to e ~ :r .100 ~ w e " AUG SEPT OCT .._OV DEC MONTHS, 1954 FrG. 22. Death rates of oysters due to D. marinum in the summer and early fall in Virginia. Data from Andrews and Hewatt ('1957). This population was taken from endemic waters and held in trays in the York River. Fifty-two percent of the oysters died of D. marinum infection in this epizootic. November, which was 87 percent of ali deaths. These oysters differed from those of the population shown in Fig. 21 in that they were natives which had always been in enzootic areas. At the northern limit of the range of D. marinum in Delaware Bay, minor epizootics are initiated each year in the period between May and August. The peak of incidence is in September or October (Anonymous, 1958). lt is believed by New Jersey investi­gators that annual mortality rates due to the fungus average only about 5 percent, with a possible maximum of less than 20 percent in the heavily infected areas of "The Cove". The rise of incidence is later in the summer than is the case in the lower Chesapeake and reaches its limited peak just prior to onset of cold weather. The period of high temperature is too short for full development of epizootics of the type found so destruc­tive in Louisiana. Complete disappearance of the disease takes place in winter or early spring (based on culture tests). In Louisiana the epizootics usually have their inception in April or May. The rapidity of development varies with environmental conditions, and with number of susceptibles per unit area. The disease in heavily enzootic areas never disappears in winter and limited epizootics may develop in unseasonably warm periods in winter. The form of epizootics is often more variable than in the Chesapeake or in Delaware Bay. Mackin and Sparks (see last paper, this volume, 1962) studied the development of epizootics at seven stations in Barataria Bay, Lake Grande Ecaille, and Billet Bay. Tray populations of 1000 oysters were placed at each station. Monthly death rates and death rates due to D. marinum, averaged from ali seven stations, are shown in Fig. 23. The hump occurring in May on the curve of total deaths was associated with "mycelial disease" ( see below) . In high salinity waters of Louisiana, spring and early summer epizootic peaks may occur which coincide with the spring tide peak; this peak usually does not occur in low salinity areas. Mean cumulative mortality in the seventh-month period shown in Fig. 23 was about 60 percent for the seven stations, and the range was from about 30 percent in the station with least mortality to 80 percent in the station developing the most severe epizootic. The percent of the total deaths attributed to D. marinum progressively increased from TOTAL DEATHS --­ 1 / I / \ / o I I I DEATHS DuE TO FUNGUS DISE ASE / I I -º p­ / / / / ,o M M MONTHS, 1957 F1c. 23. Death rates, and death rates of oysters due to D. marinum. Oysters were held in trays at seven stations in Barataria Bay, Billet Bay, and Lake Grande Ecaille, Louisiana, 1000_oysters at each station. Data are averages for ali stations. Data from Mackin and Sparks ( this volume, 1962) . Cumulative mortality was about 60 percent. early spring to September. At the same seven stations, the increase was from 26 percent in March to 100 percent in September (Fig. 24) . Experimental Epizootics in Aguaría. Epizootics initiated in aquaria by artificial infection methods culminate rapidly, and run their courses in much less time than the epizootics observed in field trays and bottom plantings. lnfection by the "injection" method ( see section on pathogenicity) produces especially sharp epizootic peaks. The progress is limited only by the number of available susceptibles and comes to an end when the population is destroyed. The developmental sequence of the epizootic is dis­torted by the high concentration of infective cells, and by the simultaneous infection of all individuals in the experimental populations. In Fig. 25 is shown the form of such an epizootic. The scatter of points at the end of the study indicates that the population was so decimated that the data carne to be based on statistically unreliable numbers of survivors. The first oyster died on the tenth day and had developed an advanced case of disease, but not the heaviest type. On the fifteenth day two oysters died with heavy disease. Only four oysters survived beyond the fortieth day and all of these were in advanced stages of disease. )() ~ 80 V FIG. '24. Percentage of total deaths of oysters dueto D. marinum in different months; 7,000 oysters were tested at seven stations in Louisiana. Data from Mackin and Sparks (this volume, 1962). The increasing deaths are correlated with temperature. o o ~ >­ (!40 ~ ~ 30 -' .. >­ a: o >-" 20 iE :;? :t' 'º / / / r / 1 / \' I 'º 20 30 40 DAYS FIG. 25. Experimental epizootic in aquaria. Oysters were "injected" with infective cells and tht first oyster died with advanced disease on the tenth day. The population was virtually wiped out bv the forty-second day. In another set of experiments in aquaria (Mackin, Ray and Boswell, 1953), oysters were "fed" the infective cells. By this method, infections are not simultaneous but take place over a period of several days, and initial infection dosage is small. The first oyster died with heavy disease on the sixteenth day and the epizootic developed in an accele­rating manner as more oysters died and liberated infective cells. In this type of aquarium epizootic 63 days were required to produce a 93 percent mortality, about twice as long a period as in the cases where the infection method produced disease in all individuals of the population simultaneously. The form of this epizootic is shown in Fig. 26. Biological Factors in Epizootiology. Several biological factors affect death rates from fungus disease and vary the development of epizootics. These will be discussed in the next sections. lnfection and lnvasion of the Oyster Host. Portal of entry of a parasite may be an important factor in epizootiology. The author (195la) believed that infective cells were ingested with food, phagocytized in the stomach and carried into the epithelium of the digestive tract of the host by the phagocytes. This still seems to be the best hypothesis, but its acceptance ~ o o ~30 o o ~ ~ ~ 20 o o ll' o 10 o o o 30 40 50 60 DAYS F1c. 26. Experimental epizootic in aquaria. Experimental oysters were fed infective cells of D. marinum. Sixty-three days were required to produce a 93 percent mortality. northerly part of the range of distribution). lt is highly unlikely that cells of D. marinum in sea water can survive cold in all stages. The hypnosp0re is probably the usual over· wintering stage; it is likely that with the beginning of spring, this cell produces spo· rangia from which come the infective cells. Andrews and Hewatt (1957) conducted studies to determine whether or not oysters may carry over-wintering stages, which produce the initial "infection" internally in the following spring. They used oysters from enzootic areas, but from which the infec· tions had disappeared during the winter. These were placed in closed aquaria at 23° to 28ºC. Although the thioglycollate tests failed to reveal any infections in these oyster populations at the start of the study, sorne oysters developed typical cases in the warm water and infected other oysters. It is not certain that this shows a special infective stage unresponsive to the thioglycollate culture diagnosis test. It may mean that when infec­tions are few, and are extremely light when they do occur, the thioglycollate test will detect the presence of the parasite only if much larger numbers of oysters are used than is usual. Andrews (1956a) infected oysters by keeping them in an endemic area. These oysters apparently lost their infections in the winter. In the spring they were transferred to low salinity areas where D. marinum does not occur. Although thioglycollate tests showed no infections when the oysters were moved, a few nevertheless developed infections in the following summer. This is taken to indicate that sorne infections do overwinter in Virginia and contribute to or originate epidemics in the summer-fall period. Whether or not oysters may harbor latent infective stages, it seems certain that popu· lations may be infected from externa) sources, after periods of complete freedom from infection. Oysters from various stations in Redfish Bay, Louisiana, in 1953 were com· pletely free from infection, as shown by repeated thioglycollate culture tests in warm weather (Mackin, 1954a). Oysters from the same hay were found to have acquired a low level infection one year later. lt is believed that these infections carne from a distant source, since oysters from ali known reefs in the Bay and "outside" in the Gulf were tested in 1953 with negative results. lnvasion and distribution of infective cells within the body of the host appear to present no problems. Phagocytic cells move freely through epithelia and connective tissue, and blood sinuses and vessels may introduce parasites to all tissues. No tissue has been found to be resistant to attack, except possibly the renal epithelium. In a sense, there are two types of epizootics caused by D. marinum. One involves populations of oysters, the other populations of host cells after invasion of a host oyster is accomplished. Since D. marinum is essentially an intracellular parasite, an individual host cell is also a host in itself. Movement from host cell to host cell is accomplished only when a host cell dies and distintegrates, liberating the contained infective cells into the blood sinuses. Sorne cells of oysters are phagocytic even when they are com· ponents of tissues other than the free blood cells proper. lnfections of these cells take place readily. Other cells seem to be actively penetrated by the parasites, by means of a lytic process, and cells of D. marinum may develop in intercellular spaces, such as the gonadal cavity, when in close contact with host cells. Defense Mechanisms. So far as is known, a combination of phagocytosis and diapede· sis is the only effective defense of the oyster against infection. By this process, parasitic cells are picked up in the tissues, and carried across epithelia into the gut lumen or to the exterior. Phagocytic cells are shed in large numbers by oysters in acute stages of disease until breakdown of phagocyte production occurs. The method of demonstration of diapedesis is to place starved oysters on a black background. Sorne hillocks of phago­cytes on the black substrate are clearly shown by this technique and tnay be shown to contain parasites by srnear or thioglycollation. Diapedesis is not usually effective in ridding oysters of DermocystUlium in warrn rnonths, when the parasites are rnultiplying rapidly. It is believed that oysters are able to free thernselves of these parasites in winter, when reproduction of the parasite ceases, if intensity of infection is not too great. In those estuarine areas where the number of infective cells is low, the phagocytes rnay be able to rid an oyster of isolated infection even in warm months. It has been observed that oysters infected in early spring rnay rid themselves of parasites in the surnrner following if extensive flushing of the estuary occurs. Ray (1959) found that in Bayou Dau Haute (Louisiana) 12 sarnples of oysters taken April 23, 1959, ali showed infections. The weighted incidence of the 12 averaged 0.36 and the incidence ranged from 20 to 60 percent. In the sarne bayou on }uly 15 of the same year, 10 sarnples out of 11 taken were free of the parasite and in the llth sarnple only one very lightly infected oyster was found. The weighted incidence of ali oysters in all sarnples on July 15 was 0.009. This decrease followed heavy local rains, and flushing freshets in the bayous. Age of the Host and lnfection Rates. Mackin (195lb) reported that young oysters, less than one year old, appeared to possess an irnmunity of sorne kind. For rnany years it has been known that the excessively high mortalities occurring in Louisiana oysters were prirnarily among the "counter" oysters. These oysters rnust rernain on beds for a longer period than do oysters raised for canning, and hence are older when harvested. Ray ( 1953) rnade a study of infection incidence and intensity in oysters less than one year old, cornpared with those older than one year, in Louisiana. He caught spat in the middle of }une, 1952, in shell bags. These spat were rnarked and hung in wire bags frorn stations in Barataria Bay. Other spat of the same age were taken on shells at the laboratory in Bayou Rigaud. Oysters known to be 11 to 12 months old from Bay Chene Fleur were cornpared with the spat. These year-old oysters at the start of the study had only a very low incidence of D. marinum. A sarnple checked by the thioglycollate rnethod at the start of the study showed ali negative, but it was known that a very low residual infection was present at Chene Fleur. Another group of oysters about four years old frorn Gardiner's Bay, Long Island, New York, was also used in the study. This group of oysters was negative for disease at the start. These groups of oysters were observed for intensity of infection for about a year. The thioglycollate method of diagnosis was used. Sarnples were taken at irregular intervals. The results of Ray's studies are surn­marized in Table 18. A study of the table shows that a very light infection appeared in one spat group about five weeks after the study started, and in the other about eight weeks after the start. These spat were six to eight weeks and nine to ten weeks old, respectively, when the infections appeared. However, no infections heavy enough to be considered "disease" appeared in either group of spat until they were approximately a year old. Even then the intensities and incidence of infection were very low cornpared to those of older oysters. The year-old Louisiana native oysters becarne infected in four weeks and in five weeks TABLE 18 Speed and intensity of infection of young oysters compared with older oysters. Data from Ray, 1953 1-year-olds 4-year-olds írom Weeks Spal group A Spal group B írom Chene Fleur Gardiner's Bay from start W.I.* I.t w.r. l. W.l. l. W.I. l. o 0.00 o.o 0.00 o.o 0.00 o.o 0.00 o.o 1 0.00 o.o 0.00 o.o 0.00 o.o 2 0.00 o.o 0.00 o.o -­·· 3 0.00 o.o 0.00 o.o 0.15 20.0 4 0.15 30.0 0.2S 30.0 s 0.00 o.o 0.08 3.8 0.35 50.0 0.10 20.0 6 1.55 70.0 7 1.35 60.0 8 0.04 3.7 0.65 40.0 1.20 60.0 9 2.00 60.0 11 0.00 o.o 12 LOO 60.0 ---­ 14 0.35 so.o lS O.S3 60.0 .... 16 o.so 50.0 22 0.07 6.6 27.S 2.55 80.0 31 0.13 6.6 36.5 2.30 90.0 40 0.27 13.3 so 0.66 37.0 Sl o.so 26.3 • W.I.=Weighled incidence. t l .= lncidence, percent. had attained a leve! of infection comparable to that of the two spat groups a year later. At twelve weeks the year-old oysters had reached 60 percent infection and weighted incidence of 1.00. The four-year-old oysters became infected at three weeks and reached a high leve! of infection of 70 percent and weighted incidence of 1.55 in six weeks. A very rapid acceleration of incidence rates and intensity of disease occurred between the fourth and sixth weeks, and heavy mortality occurred. Another group of Long lsland Sound oysters showed similar excessive acceleration of infection in the early weeks of sojourn in enzootic waters. It is assumed that these oyster populations were made up largely of highly susceptible individuals, and probably were not properly comparable to the Louisiana oysters. Andrews and Hewatt ( 1957) showed that young oysters, when fed tissue mince of heavily infected gapers, were as easily infected as were older control oysters and died as rapidly. These authors believed that young oysters fail, under natural conditions, to ingest enough infective cells to produce disease and that the "immunity" of immature oysters is due primarily to failure to ingest the minimum infective number of spores. Their hypothesis is supported by the author's studies of the effect of varying dosage of infective cells, reported in the section dealing with pathogenicity. There is sorne evidence that infection rates increase up to about four years. Density o/ Oyster Populations and lnfection Rates. lncreasing the number of oysters per unit area, while the percentage of susceptibles in the population remains constant, has the same effect in increasing infection rates as increasing the percentage of sus­ceptibles in the population when the area and the population remain constant. Density of oyster plantings, therefore, must necessarily affect infection rates, and as a corollary, degree of isolation of plantings is also important. Andrews (1957) mixed infected oysters with uninfected oysters in a tray. The un­infected oysters in this tray developed significantly higher incidence of disease than did a control tray 40 feet away which contained only uninfected oysters to begin with. Andrews concluded from this that isolation of plantings, thorough cleaning of beds, and fallowing would materially delay development of disease in oyster bedding grounds. The author found that a tray of oysters with more than fifty percent infected de­veloped a summer epizootic of less intensity than oysters in a tray 20 feet distant which started out with only uninfected oysters (Fig. 27). The uninfected tray contained highly susceptible oysters. Andrews' conclusions appear to be correct only when susceptibility is constant. On the basis of other observations, Andrews believed that reduction of number of infective cells with distance was so great that rapid infection from outside sources could be considered negligible. The author does not believe that this is always true. There are many cases of isolated populations of Louisiana oysters where infection took place over what appeared to be prohibitive distances. The case of oysters in Redfish Bay is illustrative. In 1953 a thorough check of severa! stations showed no infections in the entire hay. Oysters were tested in the laboratory under summer temperature conditions and failed to revea! latent infections. Yet in April of the following year significant infections of oyster populations had appeared in Redfish Bay. There was no apparent local source of infective elements in the Bay or in the Gulf. Redfish Bay is at the extreme tip of the active Delta of the Mississippi, and a minimum of 15 miles of fresh water separated the hay from any known source of infection, unless there is a source in the open Gulf. But oysters 1000 feet in the Gulf off Redfish Bay showed no infections in 1953. lt must be concluded that transport of infective cells may take place over long distances of open water barren of oysters. However, given a nucleus of infected oysters in a population, density of an oyster population controls to a great extent the progress of epizootics. In Louisiana, seed oysters nearly always include sorne oysters two to three years old. A normal planting is 400 to 600 sacks per acre. Such plantings contain about 8 to 12 oysters per square foot. Such /\ OYSTERS FROM NON-ENZOOTIC AREA-/ \ I \ I \ I 1 I 1 1 I \ I I I I I ' / OYSTERS FROM ENZOOTIC AREA I I / / .100 M M J MONTHS FrG. '27. Effect of introduction of susceptible oysters into an endemic area. Data from Mackin and Sparks ( this volume, 1962). One thousand disease-free oysters from a non-endemic arca were compared with a similar number from an endemic area. Infection rate was above 50 percent in the latter group at the start of the study, in Barataria Bay, Louisiana. densities must contribute greatly to the initiation of summer epizootics. Producing counter oysters in Louisiana may depend on natural reduction of plantings through disease or other factors to the point where transmission is slowed appreciably. Much study remains to be done in this field. Vead and Live Oysters as Sources of lnfection. Although infected live oysters un­doubtedly contribute to infection of other oysters, oysters dead of V. marinum infection contribute materially more. Dead oysters are shredded by crabs and small fishes, liberating uncounted infective cells into the water. Here the classic concept, that a successful parasite is one so adjusted that infection does not result in death of the host, ­ O~MEA OF FOUR CONTROLS I "' ¡;;;: o 12 24 36 48 60 72 84 HOURS F1c. 29. Effect of holding oysters out of water on weighted incidence of infection. The curve summarizes the results of three repetitive experiments in which oysters were held out of water and the weighted incidence measured in samples at intervals as indicated on the graph. epizootiological factors in reducing the summer epizootics. Sorne progress has been made in that direction. Ray (1954) pointed out severa) methods by which it may be p::>ssible to effect sorne improvement. Better methods of oyster production are needed for the entire range of the parasite. Certain established methods of combatting disea~e in commercial fisheries animals are known. Sorne of these show promise in the case of D. marinum; others appear now to have little or no practir:al value. Basic methods in combatting disease are as follows: Treatment o/ lnfected Populations with Specific Fungicides. This method appears to have the least merit in the light of present knowledge and present oyster culture practices. It is difficult to conceive of a fungicide so selective that it could (a) do no harm to the . host oyster, (b) produce no significant changes in the community of organisms associ­ated with oysters and especially those which are themselves valuable for sporting or commercial reasons, and (c) cause no redurtion in food supply. O~her obvious problems are those of costs of application, and the large amounts needed to maintain effective dosage in the face of enormous dilution. Nevertheless, there may come a time when the present wasteful hit-or-miss methods of planting and harvesting may be impossible to maintain. The European O. edulis industry has already reached that point. As methods of oyster production grow more refined, as they are in Holland and France, opportunity for effective treatment by specific fungicides may appear. For example, marketing of oysters in Holland is now done from reserves stored in artificial holding basins, which would be ideal for concentrated treatment. There are more and more attempts in our own country to produce oysters in ponds of limited size (Lunz, 1946) where conditions may be controlled. It is conceivable. therefore, that in time the oyster industry will have developed to a stage where fungicide treatment will be economically feasible. It would seem desirable, therefore, to take the first step looking toward that end. That would be to sift the large number of compounds available, and to select those found effective as fungistatic or fungicida!. If such compounds are found and are available in quantity at low cost, the second step would be to explore the possibilities of developing methods of application to large numbers of oysters in a retaining basin of sorne sort. Oysters can stand temporary storage of very large numbers in small areas, and under very adverse conditions. This fact may be the key to successful treatment. Management o/ Oyster Culture so that Ecological Conditions Are Optimum for Oysters and Mínimum for the Parasite. The best available way to take advantage of good conditions for survival and rapid growth is to shift oysters from place to place. In Louisiana the best sets occur where predation and disease are worst. To utilize these high-setting areas, provision must be made to move young oysters immediately after setting to low salinity areas. Heavy sets occur in lower Barataria each year, but the young oysters are destroyed in the first few weeks by conchs. These young oysters would become an asset to the industry if moved within a few days after setting. Dependence on natural seed reefs which must be State-maintained would not be necessary if the natural set on "barren" reefs in high salinity areas could be used. This would involve development of lattice-work barges, floated by air-filled chambers, in which culch could be systematically piled. The moving of a train of such barges to low salinity areas by an oyster lugger would entail small expense. Following a move the young oysters would have to be maintained in low salinity waters until the summer high temperature periods were past. At the end of the summer they should be returned to high salinity waters where growth during the winter months is more rapid. This first winter probably should be passed through in trays mounted on racks (Anonymous, 1940). This would facilitate removal to low salinity in early spring, just prior to reaching one year of age. These oysters in Louisiana waters would now be two inches to three inches long, single and far better stock than the usual seed oysters from the natural reefs. They would be of uniform age, uncluttered by heavy set of young oysters, and with less fouling than usual. But they must be returned to low salinity water prior to (a) the oyster setting period, (b) the advent of the new crop of young conchs, and ( c) the beginning of fungus epizootics. If in trays, transport in the lattice-work barges would be easy. In the fresh water they should be again placed on racks in trays. Toward the end of the summer, they must be returned to high salinity waters and planted on the bottom. lt is at about this time that trays will become so overcrowded that it would be necessary to redistribute them anyway. By the middle of the winter these oysters will be ready for market as raw shucked stock. Repeated removal of large numbers of oysters is expensive and the economics of the plan are uncertain, but oysters moved by means of special equipment in trays may be less costly than dredging them off the bottom each time they are moved. If the loss to fungus disease is reduced by one-half, the total crop will be more than doubled. It may be that increased yield will more than offset the increased costs. The increased value may be more than the value of the oysters saved. It will also increase as the quality of oysters is increased. Cauthron and Mackin (1953) studied methods of production in Barataria Bay, assuming that the process of moving oysters would be too expensive for general use. These authors found that when oysters set in the late summer {last part of September or early October), the young oysl'ers would pass through the following summer without undue loss to fungus disease because they would be only 8 to 10 months old. These oysters were marketable prior to the second summer when the very heavy losses from fungus disease normally occur. Spat for such culture must be taken on artificial culch ( egg-crate fillers primed with a light cement). They must also be held in trays through the first winter, but may be planted on the bottom when ~ne year old which would be in the late summer or fall. This method is successful in sorne fast-flushing bayous, where salinity is high but where conchs are not numerous because of the flushing action, including more than one-half of ali the Louisiana oyster-producing area. This method also has the advantage that dependence on the natural seed reefs is eliminated, but it has the disadvantage that tray culture is necessary. Selection o/ Naturally Resistant Strains for Seed Stock. The discovery by Andrews and Hewatt (1957) that oysters from South Carolina were resistant to effects of fungus disease to sorne extent provides sorne hope for development of resistant stock, locally or by regular importation of resistant seed from South Carolina or elsewhere. There are sorne data that indicate that populations exposed to disease in enzootic areas are more resistant to infection and lethal disease than are stocks from non-enzootic areas. The principal stumbling block for developmcnt of in situ resistant stocks is that impor­tations of susceptibles must be strictly banned. There is also the problem of preventing natural hybridization of resistant strains with susceptible stock from low salinity areas. The larvae of these susceptibles may be carried long distances. This one factor may make the development of resistant stocks in sorne areas impossible. Regular introduction of resistant seed probably has greater possibilities than has the development of resistant stocks. lf it is true that South Carolina seed are resistant to sorne degree a realistic approach to the problem is available. Objections to the in situ development of resistant stocks may largely disappear when and if pond cultures of oysters on a large scale become a reality. Pond culture itself may be the only medium through which sufficient control of cross·breeding can be exercised to make possible the in-breeding of resistance to disease. The steps in development of resistant strains must be in this order: (a) selection of resistant individuals from natural populations, (b) cross-breeding in aquaria, where all factors can be controlled, (e) transfer of the product to closed ponds for development of large vol u mes of resistant stock, and ( d) transfer to field conditions. As in other methods of disease control, a high degree of artificiality is required, along with increased cost of production. Other Parasites and Diseases STUDIES ON Nematopsis Prytherch ( 1938b) published an account of the life cycle of Nematopsis sp. which he found parasitizing oysters, and later (1940) described this gregarine as Nematopsis ostrearum. Prytherch believed that "heavy infections were found with serious oyster mortalities". These mortalities he indicated were in Mobjack Bay, Virginia, and Lake Barre, Louisiana. He claimed that high concentrations of spores were found in weak and dying oysters. These, when in adductor muscle, gill and mantle, were accompanied by paralysis, gaping, and stunting of shell growth. Prytherch (1938a, 1940) performed experiments testing lethality of Nematopsis in aquaria. He used many experimental oysters and exposed them to infection by placing crabs in the aquarium with the oysters, or in an adjacent aquarium. Control oysters were not subjected to infected crabs. The results of six of Prytherch's experiments are tabulated in Table 26. Prytherch ( 1938b) also performed duplicate experiments to these in the spring of 1938. These had lesser mortalities by 10 to 20 percent, but did not differ otherwise. Prytherch used oysters from very low salinity areas for ali these infection experiments but got his infected oysters for infecting crabs from high salinity areas near Beaufort, North Carolina, a significant factor when considering his results. He fed infected oysters to his crabs in the experimental aquaria. These oysters were, therefore, placed in the TABLE 26 Results of experiments by Prytherch (1938a, 1940) in which oysters were infected by Nematopsis sp. by exposing them to infected crabs . Ali studies lasted about three months at Beaufort, North Carolina, September to Novemher, 1937 Experimenl No. Control or Crab Mortality, oysters used experimenL hosl used perceot --------------------------------·----­ 1 250 Ccntrol Non e 7 2 250 Experiment E. depressus• 67 3 4 250 250 Experiment Control P. herbstiit No ne 84 3 5 6 250 250 Experiment Experiment E. depressus P. herbstii 46 71 • Eurypa.zw¡>ew depressu.s. t Patwpeus herbslii. experimental tanks and were shredded by crabs. There were none in the controls. It seems almost certain, therefore, that he used a highly successful method of infecting bis experimental oysters with both Nemawpsis and Dermocystidium marinum. The latter is now known to parasitize oysters at Beaufort. Prytherch could not at that time recog­nize an infection method for a fungus disease which was not discovered until ten years la ter. Sprague (1950) and Sprague and Orr (1953) described extensive experimentation with Nematopsis. Their studies were qnried out at Grand lsle, Louisiana, in 1947 and 1948. They had considerable success in infecting oysters and the alternate crab hosts and discovered that N. ostrearum produced those infections which were found pre­dominantly in the oyster mantle, while a n:ow species, N. prytherchi Sprague (1949) was found to parasitize predominantly the gills. The crab hosts of N. ostrearum were Eurypanopeus depressus, Eurytium limosum and Panopeus herbstii. The crab host for N. prytherchi was found to be Menippe mercenaria. In their studies of the effect of N ematopsis on the oyster host, Sprague (1950) and Sprague and Orr ( 1953) had resul ts very mu ch like those of Prytherch (1938), except­ing that they had much greater mortalities in controls. In sorne cases, control mortalities exceeded those of the experimental aquaria. These authors were able to recognize that there was a mortality factor in their experimentation other than the possible effect of Nematopsis. They were also skeptical that mortalities resulting from Nematopsis oc­curred under field conditions since the infections produced artificially in the aquaria were incomparably greater than any found under normal conditions. The results obtained by Prytherch, Sprague, and Sprague and Orr show that the laboratory experimentation did not give a certain answer to the question of whether or not Nematopsis was a factor in mortalities of oysters on planted beds in Louisiana. In no case was the experimentation free of the possibility that mortality factors other than Nematopsis were involved, as indicated above. Sorne other experimentation indicated that Nematopsis, with the infection intensities commonly found on oyster beds in Louisiana, is not a significant factor in mortality. Roberts (1948) compared the in­tensity of Nematopsis infections in a large number of gapers with the intensity in sur­vivors. The oysters were kept in aquaria at the Grand Isle Laboratory. When an oyster died, Nematopsis spore counts were made in mantle, adductor muscle, and heart. Results were reported as the mean number of spores per low power microscope field, ten fields being counted. There were two studies, each using oysters of different origin. The intensity of infection in gapers was compared with the intensity of infection in random­selected live oysters from the same lot. Roberts' data are summarized in Table 27. TABLE 27 Comparison of intensity of Nematopsis infection in gaping oysters with intensity in controls (live oysters) Spores per field, mean of the mean o( 10 counts in each oysle r ----­ Mantle Muscle Heart Study no. Live or gapers No. o( oyslers checked Total fields counled No. per field Total fields counted No. per field Total fi eldB counted No. per field Live oysters 12 240 67.5 240 11.3 120 2.2 Gapers 64 1280 55.5 1280 12.7 680 0.6 2 Live oysters 13 '260 63.5 260 57.6 130 3.0 Gapers 47 940 45.5 940 20.6 470 0.9 These data show that infections of oysters by Nematopsis ostrearum were no heavier in oysters that died than in live oysters. Since N. prytherchi infections are concentrated in gill tissue, this was nota valid test of this species. Extensive sampling of oysters from various beds for numbers of Nematopsis spores by Mr. Dan Wray of the Research Foundation ( 1) failed to show really heavy concen­trations anywhere, (2) showed light infections nearly everywhere, and (3) failed to show any correlation of intensity of infection with mortality rates in different areas. Owen, Walters, and Bregan (1952) found ali oysters examined in Louisiana to be infected with Nematopsis ostrearum. Oysters from low mortality areas east of the Mississippi River had somewhat heavier infections than those found in oysters in their "high mortality" area between the Mississippi River and Bayou Lafourche. They also found an increase in infection intensity in summer months at low mortality stations without correlating increase in mortality rates. The author has examined severa) thousand slides ( sections) of oyster tissues. Most of these sections show a few spores of Nematopsis, both N. ostrearum and N. prytherchi. In no case have significant histopathologies been observed in association with the spore cysts. No tissue reaction results from the spores, which do not reproduce in oyster tissues. There is no evidence that the spores produce toxins of any kind (as Prytherch believed) . Concentrations such as those claimed by Prytherch (1940) have not been found in oysters, other than those experimentally infected. He thought that spores in heavily infected oysters reached concentrations between 1 and 5 millions. Simple calculations would indicate that in an oyster 5 cms long, the number of spores per 10-micron cross section would be 500 if there were 21/z million spores in the whole oyster. But only a maximum of a couple of dozen spores has been found in any one section, though thousands of sections have been studied. "MYCELIAL" DISEASE On June 27, 1950, the author collected oysters from the Fulton Beach area of Aransas Bay, Texas. According to Dr. Gordon Gunter, oysters on reefs off Fulton Beach had recently been dying at a rapid rate, and oystermen had made complaints. No dying oysters were found, but ali oysters were very thin, sorne almost glassy. About a dozen of these oysters were fixed in Zenker's fluid and later sectioned and variously stained. In those stained with Delafield's haematoxylin, a peculiar mycelium-like growth was found, but the staining preparations were not good, and stains other than Delafield's failed to stain the organism at ali. No further studies were made at that time. In the severa! years following, the mycelium was observed several times in gaping oysters from experimental aquaria, but the observations were so isolated that effective study could not be made. In 1953 oysters in several aquaria died very suddenly. Diag­nostic cultures for Dermocystidium marinum showed that this fungus did not cause the deaths. Survivors from sorne of the aquaria were isolated in an aquarium especially reserved for the purpose, and the oysters as they died were replaced by fresh oysters in an attempt to keep the unknown lethal agent passing from oyster to oyster, so that material would be available for study after the busy period. Unfortunately time did not permit sectioning and study of the gapers at the time, but they were fixed and preserved. Later sorne of the oysters which died in this aquarium were sectioned and stained with Harris haematoxylin. These preparations showed that the mycelial organism had been carried in this aquarium of oysters for more than a year before it was finally supplanted by D. marinum. In the period from March, 1957, to September, 1957, several field studies using trays of oysters were carried out in Barataria Bay and adjacent bays. Stations were checked for mortality weekly and a high percentage of gaping oysters was recovered for study. At one station (Sugar House Bend in lower Barataria Bay) the records showed that there was a period in May when a large number of oysters died, and the culture records showed that this mortality was not caused by Dermocystidium marinum. This population of oysters hada very low incidence of fungus disease until July, when the usual summer epizootic set in. A total of about 20 percent of the 1000 oysters at this field station clied in May. The abrupt onset of mo~talities is shown in Fig. 30A, which traces the spring 2.5 2.0 ,. <( ~1.5 o ... ,.' ~ 1.0 _, ~ o: 0 o.5 JO 2 .5 2.0 ,. <( ..e._1 .5 ~ ' ~ 1.0 _, ~ ~0.5 JO A OF OYSTEl'S IN DAYS MYC E LIAL MORTALITY 8EG INS ¿ 'MAY 1 20 00 00 'º B eo'M. H[A\IY INf"ECTED SUt.4MtR EPIZOOTIC Of OERMOCYSTtOIU tr.4 <-... 74 º/o MYCELIUM F1c. 30. A. Epizootic which may have been caused by "Mycelial disease" in Barataria Bay, Louisiana, 1957. B. Epizootic caused (?) by "Mycelial disease" in Bayou Rigaud, Louisiana in 1958. Compare with Fig. 30A. mortalities by approximately weekly periods. This graph shows that immediately after the mortalities began, more than 10 percent of the oysters at the station died in a 10-day period. One hundred eight gapers were recovered (39 percent of those dying). The dead and dying oysters were sectioned and the slides stained with Harris haematoxylin, Giemsa, and Heidenhain's iron haematoxylin. Sections were cut through the visceral mass just posterior to the base of the palps. About 75 percent of these oysters was found infected with the mycelial organism. lt is believed that the incidence was actually higher, since the sectioning method is a rather small sampling of the entire oyster, and staining methods had not been worked out completely. lnitiation o/ Special Studies o/ the Mycelial Organism. The above-mentioned studies definitely associated mortalities of oysters with infection by the mycelial organism. However, except for the original dozen oysters from Aransas Bay, ali oysters studied were gapers, that is, were either dying or already dead. The Aransas oysters were taken after the mortality was substantially over. lt became desirable to determine definitely whether the mycelium attacked only dead and dying oysters, or was in fact a parasite, attacking healthy oysters, having a sequence of invasion and development in the host. To accomplish this end, several populations of oysters were placed at selected field stations in the Barataria area, one of them at the laboratory at Bayou Rigaud. About 800 oysters, including lots from several outlying areas, were placed in trays at each station. The stations were set up in January, 1958, and regular weekly checks were made beginning in early February and ending in early August. Samples of live oysters from each station were removed each week and fixed in Zenker's fluid for sectioning. All gapers collected were also fixed. The posterior gut region from each of these oysters was cultured in thioglycollate by the Ray method to permit separation of Dermocystidium disease from mycelial disease. The populations of oysters were selected on the basis of very low initial infection level with Dermocystidium marinum, to reduce the compli­cations due to impact of two diseases on one population. A typical explosive-type epizootic developed at only one of the 1958-period stations. Very conveniently, this one was at the laboratory in Bayou Rigaud. Only data from this station are presented here. Fig. 30B presents in graphic form the structure of the mor­tality developed at this station. Devel,opment o/ Mycelium in Live Oysters. Previous studies had shown that a Harris haematoxylin stain was best to show the mycelia. A slight overstain, using more acid than usual, and a quick bluing with strong sodium carbonate was found to be selective and provided a clear picture of the parasite. This method was used in staining all oysters for diagnostic purposes. Sections of live oysters showed that the attack of the mycelial organism began in early March. First infections were usually on the externa! epithelium of mantle, palps, or gills. Colonies of the mycelia were found on any external epithelial surface (Fig. 31A). They appeared to be loosely attached by a gummy material, and the filaments radiated out­ward, branching in a shrub-like manner. Frequent penetrations of the epithelium occurred. Sorne early infections were in the stomach or elsewhere in the gut. Nearly all infected oysters had internal as well as external lesions, but in the early spring these did not usually produce extensive infiltration in the tissues. Later, in April, the internal infections were more prominent, and live oysters were often found to have extensive growths, especially in the dÍgestive gland. Sixty live oysters were sectioned, which were taken in the period from March to June inclusive. Of these, the mycelium was found in 56, about 93 percent of those studied. It is believed that the incidence was actually 100 percent from inception of the attack F1c. 31. Mycelial disease in oysters. 3IA. A clump of mycelia growing attached to the externa! epithelium (mantle ) of an oyster. Section stained with Harris Haematoxylin. 31B. Stellate bodies from mycelial disease in gut of an infected oyster. These structures vary in length (from tip to tip) from S.µ to 30µ , and may be up to 3 to 4µ thick near the base. 31C. Thick mass of mycelia in a blood vessel of a gaping oyster. Here the parasite resembles an Actinomycete. 31D. Fragmenting mycelia in tissues of an oyster. These probably represent degenerating parasites. 31E. A solid staining, rounded body with strands of radiating mycelia. in March until late June. In July, incidence dropped sharply; more than 50 percent of the live oysters sectioned and stained were found to be free of the parasite. Attack on oysters in March, when Louisiana oysters are in their best condition, established the mycelium as an aggressive parasite. Gonadal development is rapid in that month, and shell growth also is good. The parasite disappeared in late summer, whert the oysters are at their poorest. lnfections in Gapers. All of the 15 gapers recovered at the Bayou Rigaud station in February were found to be negative. Beginning with gapers collected on March 4. to the middle of July, all gapers but 2 (out of 70 sectioned) were found to be infected. After the middle of July only 7 out of 19 sectioned were found to be infected and Dermocystidium marinum infection was sometimes found mixed with the mycelium. Again, the data strongly suggest that the entire population of oysters kept at the Bayou Rigaud station became infected in thc early spring, and that ali oysters carried infection to early summer. lnvolution forms of the parasite began to appear in June and July. Sections of oysters in the late fall and winter (November and December) showed that the mycelium had completely disappeared sorne time after the end of July. Characteristics of the Mortalities. No experimental studies have been made to test the degree of pathogenicity of the mycelial organism. However, the circumstances are strongly suggestive that it is in fact the cause of the mortalities because, so far as can be determined from stained sections, it is the only associated organism which was shown to attack the live oysters and to develop a progressively greater intensity of attack on the host as the epidemic developed. On the other hand, certain bacteria have been found to be more or less constantly associated with the gapers, and their presence in live oysters has not been disproved. The hypothesis of cause and effect, therefore, is only tentative. But certain features of the associated mortalities are of such interest that they are inserted here without the implication that the etiology of the deaths is proved. The most interesting of these is the selective deaths of male oysters. Although random selection of live oysters from the population prior to the onset of heavy mortality showed that males and females were almost exactly equally represented, males made up 82 percent of all the mortalities in the period of April, May and }une. Females made up 15 percent, and asexual oysters 3 percent. These latter were mostly parasitized by Bucephalus cuculus or D. marinum, both of which have a castrating effect. The heaviest mortalities in both 1957 and 1958 were coincident with spring spawning. The sections showed that gonads of gapers and live oysters alike were filled with eggs or sperm. The very rapid and explosive nature of the mortalities at the peak period is without parallel. In 1957, 20 percent of the oyster population at the lower Barataria Bay Station 6 died in May, and most of these deaths were concentrated in the first 3 days of the month. In 1958 nearly 20 percent mortality occurred in a week and most of these died in a 3-day period. In the latter year, 104 gapers were removed in 3 days from 3 trays containing a total of 655 oysters, and many boxes were removed in the same period. lt is believed that the reason for the sudden onset of mortality líes in the fact that the muscular contractions which expel eggs and sperm force large numbers of sperm through lysed openings into the sinuses of the blood system. Masses of sperm were often found in the blood of dead males, and sometimes eggs were found in blood vessels of females. Protein shock and much mechanical damage could result from large numbers of active sperm in the blood. Distended walls of the blood vessels were often observed to be penetrated by the filaments of the mycelium. Although the greater part of the deaths was associated with the spawning period, the data also showed a significant low-level mortality from March to July, associated with heavy infections of the mycelial organism. lt is believed that mortality need not always be explosive. Morphology of the Parasite, and Histopathological Effects on the Host. The parasite grows as a filamentous mycelium, branching irregularly in an arboreal fashion (Figs. 31A, C; 32, 33). When only the fine filaments with their branchings are seen, it looks and stains like an actinomycete. The natural color is a pale straw-yellow, and the cyto­plasm has a refringent appearance when unstained. ltstains lightly if at all with Heiden­hain's haematoxylin and a number of bacteria! stains, while coloring rapidly with acid haematoxylin stains, as in the Delafield or Harris method. The peculiar staining proper­ties may have been caused by the Zenker's fixative, which was used with all oysters studied. Associated with most mycelial growths are deep-staining amorphous masses (Fig. 32) which often appear to be part of the parasite, and may possibly be. Growths through such dense tissues as epithelia nearly always take place in the form of these blackened masses. These may be materials formed by tissue responses, which produce basic stain­ing, react like the mycelia, and mask the mycelia themselves. Many small, yellowish, crystalline granules invariably are found associated with the parasite. These often are left in tissues to mark the site of a former lesion. The mycelia themselves vary greatly in size. Sorne have a diameter of less than 0.5 microns and are at the borderline of resolution with the light microscope. Others may have a diameter up to 5 or 6 microns. At intervals along the mycelia structures appear­ing to be joints are occasionally found. These may be at branching points, or the filament may be sharply angled where the "joints" occur. No structures interpreted as nuclei have been observed. The basophilic reaction of F1G. 32. Characteristic infections with mycelial disease in the digestive gland and Leidig cell tissue area. The irregular black bodies in the tissue are common signs of infection. The fine brancbing mycelia have nearly dissolved a branch of the digestive gland in the center of the photograph. F1c. 33. Massed mycelia in the gut lumen of an infected oyster. The large mycdia measured 5µ thick at the thickest point. This photograph shows the peculiar type of branching sometimes observed. the cytoplasm as a whole indicates a fine dispersa! of chromatin elements. However, preparations stained with thionine may show a great many discrete, deeply-staining cytoplasmic granules of quite large size. The numbers, arrangement, and size of these granules do not suggest nuclei. General appearance of the colonies in tissue is shown in Fig. 32. Lesions involving tubules of the digestive gland are shown. Fig. 32 is a photomicrograph of a section of a live oyster. In gapers, much more extensive networks are usually found, as shown in Fig. 31C, where a thick network of the parasites has occluded a blood vessel, 01 in Fig. 33, where masses of arboroid branches fill the lumen of the anterior loop of the gut. In Fig. 31E, one of the deep-staining bodies appears to be branching in a radiating manner in transition to the mycelial form. Such masses are common and suggest that sorne of the branching structures may be jell-like and capable of retraction and projec­tion like pseudopodia of the protozoa. In many oysters "stellate" bodies (Fig. 31B) are found. These seem to be formed by germination in two or more directions from a single spore. The center from which the branches arise stain much more lightly than the branches themselves, as shown clearly in the photograph. Large "stellate" bodies were chosen for this photograph, but they occur in ali sizes down to the very minute. Clear-centered spore-like bodies are often produced at the ends of very fine branches of the mycelium. lt is assumed that the stellate bodies arise from these spores. The arms of the stellate bodies may often be found branching into typical arboroid colonies. The spores referred to above are formed in a manner suggesting that found in the genus M icromorwspora of the Actinornycetes. They appear to be attached to srnall lateral branches. In sorne slides, rnycelia rnay be found which appear to be breaking into spore-like bodies ( Fig. 3 lD) . In this stage, the cytoplasrn stains very densely, appearing black in sections. The "spores" have a pycnotic appearance, and it is believed that these repre­sent dead portions of the parasites, or involution forrns. They are useful for seeing the thin, clear, non-staining pellicle or wall of the filarnents. Growth of the parasite in the host produces little cellular reaction. Rarely are phago­cytes aggregated at the si te of lesions, and in no case has phagocytosis of parts of rnycelia been observed. Those parasites found on externa! epithelia evidently lyse the under­lying cells (Fig. 31A) causing thern to thin out and cornpletely disappear under a rnass of parasites. Leidig cells in the vicinity of an actively growing colony take on a granular, crystalline appearance, and ragged break-down areas appear. lnfected digestive gland acini sirnply disintegrate when occupied by a colony. Epithelia of the gonad, stornach, and gills likewise becarne granular in appearance and the cells dissociate. lt is suspected that the parasite rnay be toxic to the host. Heavily infected oysters stop feeding, but those with only externa! parasites, or only scattered interna! lesions seern not to be affected except locally. Distribution and Epidemiology. Distribution in Crassostrea virginica, so far as now known, includes Texas, Louisiana, Virginia, Maryland and probably rnost states of the south Atlantic. lt has also been observed in oysters, Ostrea lurida, from South Puget Sound, Washington. In Louisiana it appears to be increasing at present. Very little is known about the environrnental factors controlling the parasite. lt appears to be rather definitely a spring forrn, but is not confined to spring rnonths. Sorne heavily infected oysters have been found as late as August. Ternperatures of the water in Louisiana bays frorn March to May, when the parasite bloorns, range frorn 12° to 20ºC in March, to 20° to 29ºC in May. Surnmer ternperatures ranges frorn 27° to 32°C (June to Septernber) . Only the coldest rnonths seern to be cornpletely free of the parasite. As for the salinity, the only certain conclusion is that high salinities above 30 ppt are not inhibitory. In 1957, salinities were generally lower than usual in the period of the spring epidernic in Barataria Bay, at the Sugar House Bend Station, and were probably below 15 ppt for the rnost part. lt is probable that salinity is not a lirniting factor in distribution. So far as is known, bottorn conditions play no part. The disease has been observed rnost often in tray oysters, raised severa] inches over the bottorn. The disease occurred in Aransas Bay in oysters on a hard, raised, natural reef. In Barataria Bay, the 1957 epidernic was in an area of hard-packed sandy bottorn, and the bottorn in Bayou Rigaud is soft silt. Relationships. The "rnycelial organisrn" may be related to the Actinomycetes. There are, however, very definite differences between our forrn and the known Actinornycetes. First, no actinornycete has been reported which approaches the size of the oyster para­ site, and the very large branching forrns do not branch as do the Actinomycetes, al­ though the smaller rnycelia do. The attached colonies ( on the external epithelia) resemble the Caulobacteriaceae rather than the Actinomycetes, especially in the gumrny or waxy basal substance. The "stellate" forms and the joint-like structures have not been reported for Actinomycetes although "star-shaped aggregates" have been reported in the Myxobacteriales (Stanier, 1940). The oyster parasite resembles the Actinomycetes in the form of branching of the finer filaments, in the affinity for acid haematoxylin stains, the production of "sulphur" granules ( i.e., the yellow crystalline materials) , the refractive and slightly yellowish color of the cytoplasm, the radiating colony form and the production of spores on the tips of short fine branches, as in the Micromonospora. The differences mentioned above may be due to the fact that ali our material has been studied in the host organism, while it is customary for the orthodox researcher to record only what he finds in isolated cultures. However, it is suggested that there are also characters that remind one of the blue-green algae. A degenerate blue-green might have most of the peculiar structures observed. Literature. There are severa! references in the literature to organisms resembling Actinomycetes in oysters. One is by Orton (1924b) where he reported work by J. W. H. Eyre (see also Eyre, 1923). Eyre found "Cladothrix dU:hotomd' in sick oysters and called it a "false branching" form. Cladothrix, as pointed out by Skinner, Emmons and Tsuchiya (1947), was once used by sorne authors as a synonym for Actinomycetes. However, it is doubtful that Eyre used the word in this way for his reference to "false branching" indicates that he was assigning his Cladothrix to the iron bacteria where this genus belongs. However, Dollfus (1922) says that Eyre's Cfudothrix was a Nocardia, which is an actinomycete. Orton (1924b), using Eyre's Cladothrix, was not able to produce adverse effect on oysters in experimentation. Pettit (192la, 192lb) found what he thought was a Nocardia in sections of Ostrea edulis. He believed that the great mortality of 1919 to 1925 in English oysters was caused by this organism. He called it Nocardia matruchoti. Dollfus (1921) thought that Pettit's actinomycete was a normal cell reticulum, and denied that it was a parasite at ali. According to Dollfus (1922) A. G. R. Foulerton isolated a species of Streptothrix from the "visceral sacs" ( digestive gland?) of O. edulis. The author has seen an undoubted actinomycete in an oyster (Ostrea edulis) from Holland. It is quite possible that ali of the fragmentary reports listed above had to do with the same organism, and it may be the same as that reported here. However, the probability is that they are not the same. It would be difficult indeed for the European authors to have missed heavy infections likf. those reported here if they occurred in O. edulis. BACTERIAL PARASITE OF THE GASTRIC SHIELD OF THE VIRGINIA ÜYSTER So far as can be determined there is no mention in the literature of bacteria attacking the gastric shield of oysters. However, a bacteria] parasite exists with a very wide dis­tribution on the Gulf and East coasts of the United States. It is very common in Louisiana, in the Barataria Bay area. It is estimated that probably more than 90 percent of mature oy·sters there are infected. The parasite is commonly found on the outside surface of the gastric shield (i.e., away from the stomach epithelium) in the area where the end of the style rests. In preparations made from sections through the anterior víscera, and stained with a tissue modification of the Giemsa technique, the bacteria show on low power examination as a dark blue band along the shield section, and penetrating the shield, sometimes to con­siderable depth (Fig. 34). In the Giemsa-stained preparations, the gastric shield itself stains a light pink or bluish color. In preparations stained with haematoxylin or other F1c. 34. Section of the stomach of an oyster through the gastric shield, showing masses of bacteria growing in the surface of the shield. Stain was with Giemsa tissue stain modification. "non-bacteria!" stains, the presence of the bacteria can be detected easily by the lysed areas in the substance of the shield. The bacteria are shown by high power examination to be streptobacilli which sorne· times have quite long chains (Fig. 35). No attempt has been made to culture these interesting organisms. lt is apparent that their growth is conditioned by the proteins of the gastric shield itself and may be influenced by the enzymatic substances of the style. Nelson ( 1918) called the gastric shield "chrondroid-like" which indicates that the proteins may be of the same general nature as the gelatine of vertebrate cartilage. Yonge ( 1926) thought that the gastric shield was composed of fused cilia. Shaw and Battle (1957) apparently acecpt Nelson's hypothesis that the shield is formed of chrondrin, but suggest that it may have an origin analogous to that of the lining of the foregut of insects, in which case the gastric shield would be chitinoid. At present it is believed that the matter is not settled. If the gastric shield is chitinoid, the bacteria nourished by it may be related to the chitinoclastic bacteria, that attack chitins in bottom muds, or those parasitic in the exoskeleton of marine crustacea (for references see ZoBell, 1946) . The bacteria of the oyster resemble chitinoclasts described by ZoBell in that they adhere tightly to the surface of the gastric shield, and penetrate it. So far as the author is aware the only chitinivorous bacterium to cause disease in commercially valuable marine animals is that described by Hess ( 1937) . This one attacks lobsters on the West Coast of North America and according to the author, destroys large numbers of them. This disease is called the "soft shell" disease. There must be other such diseases. F1c. 35. High power field of a portion of the bacteria! mass shown in Fig. 34, to show the chains of bacillae. There is no reason to believe that this oyster parasite signifi.cantly damages its host. lt seems to be well balanced as a parasite and occurs in oysters which are healthy and vigorously growing. However, the effect on the host has not been investigated. It is suggested that the organism would probably culture easily and might yield information of considerable basic value. "AMBER DrsEAsE" OF ÜYSTERS In 1956, two live oysters ( Crassostrea virginica) which were observed to be a light amber color were fi.xed and sectioned. Slides revealed a parasite not hitherto seen in Louisiana oysters. The two oysters were taken from a bed north of Lake Raccourci, in one of the numerous bayous draining into that lake. The parasite was not again seen until the winter of 1958-59. A small mortality of oysters took place in that period in Bayou Rigaud, and a number of gapers were taken which had the characteristic histopathologies of the original two oysters, and the same parasites. This type of oyster parasite now is of very considerable interest because of its possible relation to the "MSX" parasite being investigated in Deleware Bay and at other localities on the East coast. For this reason 1 am presenting a preliminary description of the parasite and the histopathologies associated with parasitization by it. In Fig. 36A to D are shown various stages of the parasite as sketched from prepared slides. The most numerous stages are the more or less spindle-shaped amoebae. These commonly have from one to several filipodia or thread-like extensions of the cytoplasm, FrG. 36. Amoeboid organism causing "Amber disease" in oysters. 36A to D. Trophozoites as seen in oyster tissue, stained with Harris haematoxylin. The granules stain with any basic stain. 36 E, G. Enlargement of the nuclear structure prior to division in a trophozoite. The nature of the cap-like structure is not known. 36F. Aggregation, or result of division, in the amoeboid organism. 36 H,I,J. Various stages in nuclear multiplication and fragmentation. 36H. 4-nucleate stage. 361. B ( ? ) -nucleate stage. 36J. A cyst containing bodies that appear to be spores. 36K. Habit sketch of amoebae clinging to the wall of a blood vessel. and one nucleus. Nuclei stain with difficulty with basic dyes and often appear to be vacuoles. However, a large number of fine granules in the cytoplasm are basophilic and may be stained with any ordinary nuclear dye. Accordingly the cytoplasm appears to be very dark, and the amoeboid stages are characteristically deeply stained. The amoeboid stages are found mostly in the Leidig cell tissue, but may penetrate any tissue, and tend to congregate around the basal membranes of the gut and between tubules of the digestive gland. They often line the interior of blood vessels as shown in the habit sketch, Fig. 36K. Reproductive stages are not numerous and are much less prominent than are the amoeboid stages. The reproductive process is initiated by nuclear enlargement, and sorne of these stages (Fig. 36E) can be seen to have a definite cap on one end. This cap may be explained in either one of two ways. It may be the cell remnant from which the migrating nucleus emerges just prior to sporangium formation, which is so characteristic of one group of the Synchytriaceae, or the cap may represent a fertilizing ce!L In any event further enlargement of the nucleus takes place (Fig. 36G), followed by mitoses and nuclear fragmentation. In this early stage severa! nuclei will be found irregularly central in position (Fig. 36H). As the number increases (Fig. 361) evident cleavages of the cytoplasm occur. Apparently these can end in fragmentation as shown in Fig. 36F, or in the formation of a sporangium-like body containing spores as in Fig. 36J. These sporangia (?) are dark-staining, very thick walled, and irregularly rounded in forro. The histopathology is as striking as is the parasite. Most prominent are the masses of ceroid which form in the Leidig cell tissue. These granular masses stain dark green with Giemsa, black with Heidenhain's haematoxylin, and fail to stain ( appear yellow) with acid haematoxylin. Destruction of the Leidig cell system is extensive, and there seems to be an intense cellular reaction. Liver tubules lose their normal pigment granules, shrink and become knobby-looking in cross-section. lnfiltration of the various epithelia with parasites and leucocytes is common. Gonads atrophy, but since the parasites attack in mid-winter, it is not known how much of this to attribute to parasitism. So far as now known, this parasite is found only in Louisiana. Outside of the ob­servations given here little is known about pathogenicity, the capacity of the organism to produce epidemics, or other factors. lt appears only relatively seldom, so far as is known; possibly it is in a marginal territory in Louisiana. WATERY CYSTS OF ÜYSTERS A small percentage of the oysters in most samples taken in summer from high salinity areas have watery cysts in the visceral mass, palps, or mantle. These are not the same as the yellow pustules so commonly found in the adductor muscle or elsewhere, and have quite generally been overlooked in descriptions of diseased oysters. The cysts, seen in the live oyster, are large conspicuous bubble-like cavities, gen­erally distended by interna] pressure of accumulated fluid. Sections show these cysts to contain a central granular material usually in concentric layers (Fig. 37A). Stained sections and smears from these watery cysts show a very small bacillus in the granular materials (Fig. 37B). A number of such smears have shown what appears to be the same bacillus, so it is believed that there may be only one causative agent involved. No effort has been made to culture this bacillus. Recovery from the infection appears to take place through a sloughing of the cyst content. The cyst walls are formed of leucocytic cells which forro themselves into an epithelium similar to that of the externa] epithelium of the mantle. When fully formed, the cyst ruptures, discharging the contents to the outside. YELLOW PusTULE DrsEASE This disease is more or less frequent in oysters throughout the world, but there is no reason to believe that ali the yellow pustules and abscessed areas found in oysters have a common etiology. The yellow pustules found in Louisiana oysters are much like those in the European "maladie du pied," and like the latter usually attack the adductor muscle. Mackin and Cauthron (1952) found that in late summer 27 percent of oysters in the Barataria Bay a rea ( five stations) had the yellow ulcerations and abscesses. More than half (56 percent) of the abscesses were found to be associated with penetrations of the shell by Polydora, Martesia, or Cliona. Polydora was most effective in producing ab­scesses, probably because it introduces mud into the adductor muscle. The general appearance of the yellow pustules is shown in Fig. 38A. Smears show F1c. 37A. Section of oyster showing a watery cyst in the palp. This cyst is lined with epithelium. 37B. Bacteria! smear from a watery cyst. The bacteria appear to be very small, short rods. that they are filled with enormous numbers of moribund leucocytes in the cytoplasm of which are large numbers of basophilic granules. Stained with Giemsa these granules are purplish-blue and about 0.3 to 0.4 microns in diameter (Fig. 38B). They will also stain with iron haematoxylin and acid haematoxylin, and seem to be degeneration products. Bacteria may or may not be found in smears and may or may not develop on plates inoculated from abscess. Sorne abscesses seem to be sterile. In many cases leucocytes from absecesses contained inclusions of large size. These also do not appear to be parasites or to contain nuclei. Bacteria when found in the yellow pustules are of varied type. None appear to be constantly present, and it is believed that most, if not all, are introduced saprophytes. The oyster appears to be capable of isolating and destroying these bacteria in most cases. Observations indicate that only a small percentage of all abscesses result in death of the oyster; these are usually associated with the adductor muscle, having been formed around mud introduced through Polydora burrows. The common "muscle pearls," nacreous excrescences in the muscle scar, represent healed abscesses in the muscle tissue. The abscesses described here should not be confused with those caused by D. marinum. The latter do not have the yellow color. This yellow color is intensified in the bacteria! pustules under ultraviolet light with a black light filter, which often shows the entire oyster to be a yellowish color, or makes certain large mantle arteries show as yellow lines. The normal color of oysters viewed by ultraviolet light is a sky blue. F1c. 38A. Oyster with a very large yellow pustule in the anterior edge of the adductor muscle. Note the thickened appearance of the mantle vessels under conditions of disease. 38B. Amoebocytes of the oyster from a yellow pustule. Thc small spherical inclusions are characteristic; stain with basic stains. Yellow pustules do not ordinarily pose a great economic problem. Few oysters are marketed when the pustules are most common, in the high temperature period of late summer. Most oysters are thin and low in glycogen in that period, and by the time they are fattened in late fall most of the pustules have disappeared. lsolation by fibroid capsules and by epithelium formed from massed leucocytes often takes place, followed by sloughing of the entire pustule. These cast-off pustules may occasionally be found in the shell cavity, and may be covered with thin layers of shell by the mantle. ÜLIATE PARASITE OF ÜYSTERS A species of ciliate parasite of oysters is distributed over the Atlantic and Gulf coasts of the United States. Richardson ( 1938) mentioned a ciliate protozoan from Charlotte­town, Prince Edward Island, Canada, which parasitized oysters and which he placed in the genus Orchiwphrya. If this parasite is the same as the species here descrihed, Richardson's placement would seem to be in error. Richardson was able to transmit ciliates from host to host. The ciliates are about 12 to 15 microns wide and 40 to 50 microns long. The macronucleus is ovoid and massive. The micronucleus occupies a vesicle either anterior to or posterior to the macronucleus but is never lateral to it. The anterior end is pointed, and encased in a long sheath is a needle-like retractile stylus with which it fixes itself to the digestive epithelium of the host. The ciliary rows are slightly spiraI, about 14 or 15 in number. Contractile vacuoles are ordinarily not ohserved, but sometimes there may be up to three very small ones distributed from near the anterior end to the posterior extremity. This parasite probably is the same as Ancistrocoma pelseneeri, a widely distributed parasite of species of Mytilus. This parasite is usually rather rare in healthy oysters, but in diseased oysters it is often found in large numbers in the stomach or intestine, and may penetrate the ducts and tubules of the digestive gland. It may become a complicating factor in Dermo­cystidium marinum infections but there is no reason to think that it has much inde­pendent effect on the host. Frc. 39. Ciliates in the stomach of an oyster. They cling to the epithelium by means of a spear-like structure which can be retracted. Fig. 39 is a photomicrograph of parasites in the stomach of an oyster. The row of ciliates here were originally attached to the epithelium but were detached by shrinkage due to fixation. Acknowledgments Studies of disease in oysters involved a considerable part of the personnel of Project Nine stationed at Grande Isle and ali of the staff of Project Twenty-three. Full acknowl­edgment andan account of project administration is given in the preface to this volume. The author is especially grateful for assistance by Mr. Dan Wray, who accomplished much of the field work and made many slides for study in 1948 and 1949. Mr. James L. Boswell assisted in these studies from 1950 to 1960, and has accomplished much of the technical work during that period. Dr. Sewell H. Hopkins had advised in the work since the beginning of the studies. Appendix This appendix includes records of distribution of D. marinum in Louisiana collected by the Texas A & M Research Foundation Laboratory at Grand Isle, Louisiana, 1948 to 1959. Locations are listed in five regions; arranged from east to west. Bays and bayous are arranged generally in their order of location beginning near Mississippi Sound east of the Mississippi River and following clown the east side of the river, around the end of the Mississippi River Delta, back along the west flank of the Delta to the north­west thence across the Barataria, Timbalier, and Terrebonne basins, to the Atchafalaya River, with one record west of this river. In the listing below, the hay or bayou named is underlined, the date of collection of the sample follows the name of the hay, followed by ( 1) the number of oysters in the sample, (2) the incidence of infection in percent, (3) the weighted incidence of in­fection, ( 4) oyster lease number if known. lf a sample is too small for computation of incidence and weighted incidence, the location is given only as a positive identification of D. marinum, along with the date if known. After the underlined name of a hay, bayou or location, the samples in that location are continued to the next semicolon. If more than one sample is collected in the same hay or bayou on the same date, the data for the individual samples are separated by a"+" sign. Determinations based on gapers are indicated by the letter (G) at the end of the entry, ali others are based on live oysters. Superscripts refer to the following: a, See station 1 records (Mackin and Sparks, 1962) ; b, station 7 records, ibid; e, station 2 records, ibid; d, station 3 records, ibid; e, station 5 and 6 records, ibid; f, station 7 records, ibid; g, Mackin and Wray (1952). l. A rea east of the Mississippi River; Mississippi Sound to Alexis Bay. Bayou Marron, 7-12-58/ 25(1> /0.0(2 J/ 0.0(3) / 14529(4); North Lake of Bayou Marron, 7-12-58/ 25/ 0.0/0.0/ 14590; Black Bay, 8-24~51, at Stone Island, Gallego Island, and Lonesome lsland; Bay Craba, 8-23-51, at S.E. end of Bay Gardene, 1-20-59/ 25/ 12/ 0.10; Long Bay, 8-23-51, east end, 3-10-50/ 6/ 17/ 0.77/ 8269; Uhlan Bay, 6-9-59/ 10/ O.O/ O.O+ 10/ 50/ 0.9 + 10/ 0.0/ 0.0, 9-3-59/ 2/ 0.0/ 0.0 + 10/ 0.0/ 0.0 + 5/ 40/ 0.3 + 5/ 40/ 0.4 + 10/ 0.0/ 0.0 ; ]ulius Bayou, 2-5-59/ 40/ 40/ 0.38/ 13556; California Bay, 6-29­48, at California Point, 8-23-51, W. end of Bay, Middle of Bay; Bay Denessee, 9-10-58/25/40/0.64 + 25/44/1.16 + 25/36/0.68; Old Stump Bay, 7-3-59/ 30/ 53.3/ 0.90 + 7-3-59/2/50/2.5 (G); Grand Bay, 3-6-59/ 20/ 40/ 0.58, 12-7-58/10/ 50/ 0.75 + 10/ 30/ 0.20 + 15/ 73.3/ 1.77; Drunken Bayou, 12-14-57/ 25/ 48/ 0.60, 7-24-58/50/ 20/ 0.22; Alexis Bay, 7-24--58/ 30/ 26.6/ 0.57. 11. In area around the end o/ the Mississippi River; active Delta area. Redfish Bay, 3-20-57/ 20/ 20/ 0.20 + 25/ 56/ 0.92, 7-3-53/ 45/ 0.0/ 0.0, 7-14-53/25/ O.O/ O.O + 17 / O.O/ O.O, 7-15-53/ 16/ 0.0/ 0.0 + 12/ 0.0/ 0.0, 4-14--54/ 25/ 8.0/0.25; West Bay, 10-25-55/ 13/ 0.0/ 0.0 (G); Tiger Pass, 12-2-52/ 5/ 0.0/ 0.0. 111. Spanish Pass to Grand Bayou; west fiank o/ the Mississippi above the active Delta. Cane Bayou, 5-15-57/ 22/ 80/ 1.60; Spanish Pass, 5-15-57/ 20/ 55/ 0.95 + 25/24/ 0.16; Bay Tambour, 10-18-49/ 4/ 50/ 0.50, 8-12-53/ 25/ 32/ 0.36/ 11728, 8-10-57/ 19/ 0.0/ 0.0/ 14526, 8-28-58/ 25/ 0.0/ 0.0/ 14526 + 25/ 0.0/ 0.0/ 13628 + 25/4.0/ 0.12/ 14526 ; Sandy Point Bay, 8-11-53/ 25/ 88/ 2.20/ 11725 + 24/ 33/ 0.60/ 12988, 8-12-53/ 25/ 72/ 1.92/ 11213, 8-10-57/ 13/ 0.0/ 0.0, 8-28-58/ 25/ 8.0/ 0.06/ 13695; Bay ]acque, 10-18-49/ 4/ 100/ 3.0, 8-17-53/ 25/ 72/ 1.92/ 10455 or 10456, 8-18-53/ 25/60/ 1.34/ 9851 ; Bay Chi Charas, 8-26-53/ 25/ 84/ 1.18/ 12627; Chi Charas Bayou, 3-30-59/25/ 12/ 0.14 ; Bay Coquette, 6-25-51/ 1/-/l.O (G) , 8-23-53/ 25/ 36/ 0.50/11325 (G); Cyprian Bay, 7-3-51/ 1, Fasterling lease 262, 8-26-53/ 25/ 76/ 2.36/ 10762, 8-27-53/ 25/ 76/ 1.86/ 10164, 9-5-53/ 25/ 16/ 0.28/ 13100, 7-27-53/ 25/ 92/ 2.10/ 10464 + 25/ 76/ 1.34/ 12752, 7-28-53/ 24/ 75/ 1.17 / 12221, 7-29-53/ 21/ 67 / 1.17 / 9212; Bayou Cop-Cop, 8-31-53/ 25/ 76/ 1.10 ; Dry Cypress Bayou, 9-5-53/ 25/ 76/ 1.84/ 12751; Pizatta Bay, 1-31-55/ 25/36/ 0.26 + 20/ 35/ 0.25; Bay Skipjack, 10-18-49/ 6/ 50/ 2.16, 7-2-51/1, Vodopija lease 659, 8-27-53/25/ 92/ 2.50/ 10453, 8-28-53/ 25/ 84/ 2.28/ 10453; Scofield Bay, 7-19-51/1/ -/5.0/625 (G); Scofield Bayou, 5-3-56/25/64/0.62, 8-29-51/ 1/-/ 5.0/635 (G); Bay Pomme D'or, 12-1-55/ 19/ 63/ 0.71/ 17600, 7-3-51/ 1, Fasterling lease 570, 8-19-53/24/67/1.23, 10-18-49/4/ 75/1.25; English Bay, 10-18-49/ 10/ 40/ 1.00, 7-3-51/ 1, Emmett Hingle lease 320, 8-27-53/ 25/ 88/ 2.56/ 11831; English Bayou, 9-3-59/ 34/ 35/ 0.62 ; Fasterling Cut, 9-5-53/ 25/ 76/ 1.60/ 11858; Bayou Trouve, 8-26­53/ 25/ 92/ 2.72/ 10446; Bayou Fontanelle, 8-29-51/ 1/ -/ 5.00/ 10661 (G), 7-4-51/ 1/ -/ 3.00 ( G) ; Bayou Borne, 9-5-53/ 25/ 68/ 1.66/ 10741 ; Bastian Bay, 12-1-55/ 20/ 55/ 0.75/ 10046, 9-6-56/ 6/ 0.0/ 0.0, 10-18--49/ 8/ 63/ 1.62; Bayou Cook, 10-18-49/ 6/ 67/ 1.33; Little Bay Cherie, 11-1-55/-/-/ 0.82, Frank Jurisich, near upper Adams Bay; Adams Bay, 1-26-56/25/ 64/ 0.96/ 11863, 10-18-49/ 4/ 100/ 1.00; 11-30-55/ 4/ 0.0/ 0.0/ 11863 (G), 7-19-51/ 1/-/5.00/ 833 (G) ; Bay de la Cheniere, 12-14--54/ 15/ 13/ 0.33; Bay Lanaux, 9-24--58/ 40/ 22.5/ 0.45/ 13420, 2-7-52/ 26/ 50/ 0.54; Grand Bayou, 6-20-56/ 50/ 60/ 1.07, 5-28-57/ 23/ 65.2/ 1.13 + 22/ 31.8/ 0.80, 6-20-56/ 2/ 50/ 2.50 (G). IV. Grand Bayou to Bayou Lafourche. Lake Washington, 5-17-55/ 25/ 84/ 1.28 + 24/ 42/ 0.94; Lake Robinson, 12-16-59/ 33/ 12/ 0.12 ; Bay Catherine & Bayou, 11-27-56/ 25/ 44/ 0.72/ 13283; Billet Bay, 2-5­59/ 40/ 42.5/ 0.55, 8-7-58/ 60/ 55/ 0.65, 12-30-53/ 25/ 72/ 0.88/ 12861+25/ 84/ 1.36 + 25/ 80/ 0.94, 2-5-54/ 25/ 72/ 0.86/ 12861, 5-11-54/ 25/ 68/ 0.98 + 25/ 52/ 1.07, 5-25­54/ 25/ 80/ 1.27, a, 1-24-57/ 20/ 75/ 1.12; Freeport Sulphur Company dredged cut, 1­23-57/ 25/ 52/ 1.08; 2-8-57/ 20/ 75/ 1.40, b; BayouLaMer, 2-5-54/ 15/ 80/ 1.20; Rattle­ snake Bayou, e; Grande Ecaille, 10-8-49/ 21/ 52/ 0.76, 11-27--49, Eastern Grande Ecaille, 12-21-51, Western Grande Ecaille, d, 1948--49/ 13/100/ 5.00 (G) ; Four Bayou Bay, 3-2-56/ 25/ 68/ 1.44/ 13140 ; Bay Baptiste, 7-20--49, Zibilich lease, 1949-50/ 27/ 100/ 4.70 (G); Barataria Bay, 10-16--54/ 25/ 68/ 0.92/ 13389 + 20/ 50/ 0.45/ 9457 + 11/ 55/ 0.95/ 9728 + 25/ 52/ 0.92, 10-18-54/ 25/ 60/ 0.78, 10-25-54/ 25/ 64/ 1.06, 3-21­55/25/40/0.50/9571, 3-28-55/25/44/0.62, 3-30-55/25/16/0.24/9942, 3-31-55/25/ 52/ 0.58/ 12887 + 25/ 44/ 0.85 + 25/52/ 0.62/ 12887, 4-22-55/ 25/ 56/ 0.92, 8-31-55/ 15/ -/ 0.77/ 12899 + 10/ -/ 0.25/ 12899 + 15/-/2.17 + 10/-/1.55 + 10/ -/ 1.20, 8-19­49/ 31/ 35.5/ 0.55, 10-5--49/ 23/ 52/ 0.87, 4-3-50, 9578, W. of Queen Bess lsland, near Bird Island, 8700, near Mendicant Island (S.W.), 8120, S. Barataria, 9557, Grand bank (S.E.) , 1-23-51/ 8/ 12.5/ 0.125/ 8902, 2-8-51, 8902, Middleground, 3-21-51, West of Big Island, 9-15-53/25/40/1.02/10764, 3-28-57/13/61/0.88, g' 8-31-55/6/-/3.l, May to Aug. 1949/ 25/ 100/ 5.00, 10-5--49/ 15/ 100/ 5.00, 11-8--49 to 4-22-50/ 15/ 93/ 4.66 (G), Sugar House Bend, • ; Sugar House Bayou, 5--30-51/ 7/ 14/ 0.14, 1-15-57/ 25/ 80/ 1.26, r; Bay Chene Fleur, 1-20-54/ 1/ 0.0/ 0.0, 1-6--55/ 25/ 80/ 0.90, 1-5-51/ 25/ 40/ -; Little Bay Chene Fleur, 2-24-60/ 15/ 0.0/0.0; Wilkinson Bayou, 10-6--49/ 26/ 0/ o.o, 1-5--51/50/40/0.64, 2-7-51/20/15/0.15, 3-3-51/20/5/0.05, 4-4-51/20/20/0.30, 5--9-51/ 20/ 5/ 0.25, 6--5--51/ 20/ 15/ 0.15, 7-6--51/ 20/ 10/ 0.10, 8-7-51/ 20/ 20/ 0.35, 9-4-51/ 20/ 35/ 0.45, 3-22-52/ 44/ 24/ 0.29, 4-16--52/ 20/ 0/ 0.0, 6--25--52/ 25/ 0/ 0.0, 9-30-52/ 25/ 28/ 0.32 + 25/ 72/ 1.50, 1-14-53/ 50/ 50/ 0.72, 7-20-53/ 25/ 40/ 0.48, 4­20-54/ 25/ 76/ 1.92, 1-6--55/ 25/ 80/ 0.90, 1-9-56/ 25/ 40/ 0.52, 1-9-59/ 25/ 32/ 0.24, 3-3-59/ 50/ 6.0/ 0.15, 12-18-59/ 25/ 32/ 0.24, 2--4-58/ 25/ 24/ 0.16, 2-24-60/ 50/ 0.0/ 10.0; Hackberry Bay (Bay Du Chien, N.W. of Barataria), 8-4-52/ 15/ 20/ 2.00/ 10864 + 15/ 0.0/ 0.0/ 10186 ; Manilla Bayou, 5--1-56/ 47/ 4.0/ 0.04 + 37/ 0.0/ 0.0; Bassa Bassa, 10-7--49/21/ 38/ 1.33, 10-7--49/ 17/88/ 3.59 (G); Creole Bay, 10-26--49, 10364; Bay des lslettes, 1-7-54/ 25/ 84/ 0.60/ 13205; Bayou Rigaud, 10-3--49/ 21/ 67/ 1.14, Re­search Found. Bayou Rigaud Lab., May, 1949/ 3/ 33/0.33, Oct., 1949/ 21/ 67/ 1.14, April, 1950/ 6/ 33/ 0.33, June, 1950/ 7/ 86/ 2.07, Feb., 1951/ 20/ 40/ 0.60, Mar., 1951/ 20/ 10/ 0.10, April 1951/ 20/ 45/ 1.00, May, 1951/ 20/ 30/ 0.30, June, 1951/ 20/ 65/ 1.45, July, 1951/ 20/ 90/ 1.70, Aug., 1951/ 20/ 85/ 1.45, Sept., 1951/ 20/80/ 1.40, 4-4-52/ 25/ 52/ 0.88, 8-21-52/ 10/ 100/ 2.20, 3--4-52 to 5--31-52/ 279/ 70/ 1.35, 8-29-52/ 14/ 93/ 0.96, 9-26--52/ 25/ 56/ 0.64, 9-29-52/ 25/ 76/ 1.56, 3--4-53/ 25/ 52/ 0.72, 3-25--53/ 25/ 84/ 1.78, 4-13-53/ 25/ 88/ 1.90, 5--6--53/ 25/ 96/ 1.70, 10-10-58/ 25/ 76/ 1.36, 1-6--59/ 21/ 81/ 2.33, 2-6--59/ 8/ 25/ 0.38, 6--4-59/ 5/ 40/ 0.40; Bayou Rigaud, 1948-49/ 21/ 95/ 4.38 (G); Caminada Bay, 6--26--51 , 9485, 10355, 10769, 8725, 9395; Bayou Souris, 1-10-55/ 25/ 36/ 0.26 ; Bayou Thunder Von Tranc, 12-28-53/5/ 100/ 0.90; Bayou Fer Blanc, 4-25--57/ 18/ 78/ 2.08 + 4/ 75/ 1.13 + 25/ 96/ 2.52; Bayou Laurier, 3-5--56/ 25/ 76/ 0.72/ 12823; Bayou Lafourche, 1-19-54/ 25/ 28/ 0.20. V. Bayou Lafourche-W est. Panama Canal, 1-19-54/ 25/ 60.0/ 1.04; Little Lake, 7-12-58/ 50/ 52/ 0.70, 2-27-59/ 25/ 20/ 0.24, 3-25--59/ 26/ 12/ 0.08 + 26/54/0.71, 10-29-53/ 25/64/1.84; Deep Bayou, 10-29-53/ 25/ 80/ 1.72; Bayou Blue, 7-20-56/ 25/ 72/ 1.44 + 25/ 56/ 1.06, 8-10-51, (South of Little Lake); Lake Raccourci, 3-14-58/ 25/ 40/ 0.58/ 13883, 10-18-58/ 25/ 60/ 0.82/ 13883, 4-9-52/ 11/ 90.0/ 2.0 + 19/ 52.6/ 1.37; Bay De Millieux, 3-12-56/ 25/ 76/ 0.84/ 12429 & 12106, 11-1-55/ 25/ 48/ 0.58/ 10370; Bayou Mulet, 11-8-55/ 25/ 48/ 62/ 14191; Bayou Rosedaux, 11-2-55/ 25/ 72/ 0.92/ 12429, 11-9-55/ 25/ 76/ 1.30/ 12429, 224 Oyster Disease Caused by Dermocystidium marinum 11-10-55/ 25/ 52/ 1; 12/ 12429; Bay Rosedaux, 11-14-55/ 25/ 76/ 0.98/13333; Bayou Demi !ohn, 3-12-56/ 25/ 68/ 1.08/ 11323; Little Bay Rosedaux, 3-12-56/25/56/ 0.64/ 10100; Bay A Taton, 2-15-56/ 25/ 56/ 1.02, 2-18-56/ 25/ 60/ 1.10; Chinaman Bayou, 11-3-53/ 25/ 56/ 1.80; China Bayou, 11-14-55/ 25/56/0.62/9400, 11-14-58/25/24/ 0.22; Bay Courant (Bay Chinois) , 3-6-56/ 25/ 60/ 0.72/ 11916, 3-8-56/25/ 68/1.20/ 12219 & 12191; Bayou Courant, 3-8-56/ 25/ 88/ 1.14/ 11327 + 25/ 80/ 1.24; Bay Plais­sance, 2-19-56/ 25/ 44/ 0.66; Bayou Platte & Grosch, 3~6-56/25/80/0.96/12822 + 20/ 60/ 0.60; Bayou Grosch, 3-ó--56/ 25/ 68/ 1.12/ 13330; Bayou Du Nord, 3-2-56/25/ 76/ 1.08/ 12824 +25/ 68/ 0.94/ 12824; Bay Marselin, 2-27-56/ 25/ 80/ 1.36/ 12422; Bay Tambour (above Raccourci) , 2-28-56/ 25/ 52/ 0.58/ 12568 + 25/ 56/ 0.82; Pass A !ohn, 6-21-58/ 70/ 65/ 1.56; Bay Gray (Grey), 2-28-56/ 25/ 72/ 1.08/ 12233, 7-4-58/ 15/ 87/ 1.60 + 10/70/ 1.75 + 2/ 50/ 0.26; Deep Lake (Lake Creaux), 2-27-56/25/76/1.16/ 10815 + 25/ 92/ 1.48, 11-3-53/ 25/ 52/ 1.28; Middle Bayou, 2-28-56/ 25/ 68/1.04/ 11748; Bayou Du Chien, 3-1-56/ 25/ 28/ 0.26/ 10518, 3-2-56/ 25/64/0.54; Bayou Point Au Chien, 1-14-58/ 25/ 24/ 0.20; Timbalier Bay, 10-25--55/ 25/ 84/ 1.56, 10-15--52/12/ 75/ 1.50, 1-19-54/ 25/ 68/ 1.26; Grand Bayou Felicity, 10-15-52/12/ 50/1.05; Lake Felicity, 11-3-53/25/ 76/2.64; Lake Chien, 11-4-58/30/ 40/0.67; Bayou Dau Haute, 4-23-59/ 10/ 30/ 0.45 + 5/ 40/ 0.30 + 5-20-0.60 + 5/ 20/ 0.10 + 5/ 20/ 0.80 + 5/ 60/ 0.40 + 5/ 60/ 1.00 + 5/ 60/ 0.40 + 5/ 20/ 0.20 + 5/ 40/ 0.30, 7-15-59/ 5/ 0.0 + 5/ 0.0 + 5/ 0.0 + 5/0.0 + 5/ 0.0 + 5/ 0.0 + 5/ 20/ 0.10 + 5/ 0.0 + 5/ 0.0 + 5/ 0.0 + 5/0.0 + 5/ O.O; facko Bay, 10-29-53/ 25/ 76/ 2.06; Lake Barre, 8-10-51, (at Barre Oil Field); Bayou Bas Bleu, 10-21-49, (Research Found. planting); Bayou Bourbeux, 11-12-53/ 25/ 72/ 1.56; Petite Caillou, 10-6-54/ 25/ 100/ 1.88; Bay Ste. Elaine, 8-10-51, (at Ste. Elaine camp); Rat Bayou, 12-1-53/ 25/ 68/ 1.04; Bay La Mat, 12-1-53/ 25/ 68/ 0.76; Bayou Billiot, 12-1-53/ 25/ 60/ 0.86 + 25/ 36/ 0.24; Moss Bay, 1-12-54/ 25/56/ 0.76; Oak Bayou, 12-3-53/ 25/ 72/ 1.36; Deer Bayou, 12-3-53/ 25/ 56/ 1.12; Lake Pelto, 2-21-54/ 25/68/ 0.62 +25/ 60/ 0.82; Round Lake, 2-21-54/25/60/0.64; Dog Lake, 12-4-53/ 25/92/ 2.12; Bayou Du West, 2-3-54/ 25/ 56/ 0.78; Hackberry Bay (West of Lafourche), 12-14-56/ 20/ 45/ 0.75, 12-8-49, South portion; Bayou East of Hackberry Bay, 12-4-53/25/72/1.44; South end of Bayou connecting Dog Lake & Hackberry Bay, 12-4-53/ 25/ 84/ 2.02; Bayou between Hackberry Bay & Dog Lake, 12-4-53/ 25/ 76/ 2.08; Sister Lake, 1-9-52; Lake Mechant, 12-16-52/ 40/17/0.17 + 35/14/0.14; Mud Hale Bay, 9-5-56/ 16/ 93.7 / 2.12/ 11315, 2-20-56/ 25/ 64/ 0.98/ 11315 +25/ 52/ 1.08/ 9827; Bannan Bay, 2-3-54/ 25/ 40/ 0.66; Oyster Bayou, 2-18-60/ 40/ 7.5/ 0.05; Tribu­tary of Oyster Bayou, 2-18-60/ 30/ 10/ 0.08; funop Bay, 2-3-54/ 25/ 56/0.46; Atchaf­alaya Bay, 6-2-55/ 25/0.0/0.0, 7-12-53/15/0.0/0.0, 5-5-54/25/0.0/0.0 + 25/ 0.0/ 0.0, 7-15-54/ 25/ 25/ 0.0/ 0.0, 11-28-50/ 5/ 0.0/ 0.0 + 8/ 0.0/ 0.0; Little Constance Bayou, 11-25-5:3 / 25/ 72/ 0.66. 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Dermocystidium marinum, a parasite oí oysters. Parasitological Reviews, Exper. Parasit., 4(2): 172-200. *Ray, S. M. and J. G. Mackin. 1954. Studies on the transmission and pathogenicity oí Dermo­cystidium marinum, I. Texas A & M Research Foundation Project 23, Tech. Report No. 11, p. 1-11. Ray, S. M., J. G. Mackin and J. L. Boswell. 1953. Quantitative measurement oí the effect on oysters of disease caused by Dermocystidium marinum. Bull. Mar. 'Sci. Gulf Carib. 3: 6--33. Reichenback-Klinke, H. H. 1950. Der Entwicklungskreis der Dermocystidien sowie Beschreibung einer neuen Haplosporidienart Dermocystidium percae n. sp. Verhandlungen der deutschen Zoologen vom 2, bis 6. August, 1949. In Mainz, Verhandl. deut. zoo!. Ges. 1949, 126--132. Reid, R. O. 1953. Addendum: Statistical C<>mputations. /n Ray, Mackin, and Boswell, Bull. Mar. Sci. Gulf Carib. 3 (1) : 24-32. Remy, P . '1931. Presence de Dermocystidium ranae Guyenot et Naville, chez une Rana escalenta L. de Lorraine. Ann. Parasit. 9: 1-3. Richardson, L. R. 1938. Report on a preliminary study of the endozoan fauna of oysters from Malpeque and Charlottetown waters. Fisheries Research Board of Canada, Manuscript report No. 147. *Roberts, J. N. 1948. Results of the Nematopsis mortality investigation (July-November 1947). Texas A & M Research Foundation Project Nine, typed copy. Rühberg, W. 1933. Uber eine Hefeinfektion bei Daphnia magna. Arch. f. Protistenk. 80: 72-100. SchnPider. A. 1884. Sur le development de Stylorhynchus longicollis. Arch. Zoo!. exper. et gen., Ser. 2, 2 : 1-36. Shaw, Barbara L. and Helen I. Battle. 1957. Thc gross and microscopic anatomy of the digestive tract of the oyster Crassostrea virginica (Gmelin). Can. J. Zoo!. 35: 3'25-347. Sigot, A. 1931. Une Chytridiaceae nouvelle, parasite des oeufs de Cyclops. C. R. Soc. Biol. Paris 103: 34--37. Skinner, Chas. E., C. E. Emmons and H. M. Tsuchiya. 1947. Molds, yeasts, and actinomycetes. John Wiley &Sons, New York. Sprague, Victor. 1949. Species of Nematopsis in Ostrea virginica. Parasitology, 35(6): 42. (A reprint in Nat'l Shellf. Assoc. Convention Addresses for 195'.2, p. 25.) *Sprague, Victor. 1950. Studies on Nematopsis prytherchi Sprague, and N. ostrearum, emended. Texas A & M Research Foundation, Project Nine, p. 1-59. Sprague, Victor and P. E. Orr. '1953. Studies on Nematopsis, III. N. ostrearum and N. prytherchi with special reference to host-parasite relati<>n. Nat'l Shellf. Assoc. Convention Addresses, 1952, p. 2fr43. St. Amant, Lyle S. 1957. Sorne trends in the bie>logical investigations of various oyster problems in Louisiana, Convention paper, Nat'I Shellf. Assoc. Miami Beach, Nov. '1956. St. Amant, Lyle S., A. V. Friedrichs and Emory Hajdu. 1958. Report of the Biological Section, Oysters, Water Bottom and Seafood Division. Seventh Biennial Report, Wildlife and Fisheries Commission, 1956-57, p. 71-92. Stanier, R. Y. 1940. Studies on the Cytophagas. J. Bact. 40: 619-63'5. Stauber, Leslie A. 1950. The fate of India ink injected intracardially into the oyster, Ostrea virginica Gmelin. Biol. Bull. 98(3): 227-241. Stein, J. E. and J. G. Mackin. 1'955. A study of the nature of pigment cells of e>ysters and the relation of their numbers to the fuugus disease caused by Dermocystidium marinum. Texas Jour. Sci. 7(4): 422-429. *Stein, J. E., and J. G. Mackin. 1957a. A histochemical study of the glycogen content of oysters infected by Dermocystidium marinum. Texas A & M Research Foundation, Project '23, Tech. Report No. 20. Stein, J. E. and J. G. Mackin. 1957b. An evaluation of the culture method used in determining the intensity of Dermocystidium marinum infections in the oyster Crassostrea virginica. Texas A & M Research Foundation, Project 23, Tech. Report No. 22, p. 1-5. Tregouboff, G. 1913. Sur un Chytridiopside nouveau, Chytridioides schyzophylli n. gen., n. sp., noraq;te de l'intestine de Schzyophyllum mediterraneum Latzel. Arch. Zoo!. exper. et gen. 52(2): 25-31. Weiser, J. 1943. Beitrage zur Entwicklungsgeshchichte von Dermocystidium daphniae Jirovec. Zoo!. Anz. '142: 200-205. Weiser, J. 1949. Parasites of fresh-water fish. l'I. Vestnik Ceske Zoo!. Zpolec. 13: 364-371. Yonge, C. M. 1926. Structure and physiology of the organs of feeding and digestion in Ostrea edulis. J. Mar. Biol. Ass. U.K. 14(2) : 295-386. Zacherie, F. C. 1898. The Louisiana oyster industry. Bull. U. S. Fish. Commission for 1897: 297-304. ZoBell, C. E. 1946. Marine microbiology. Chronica Botanica Company, Waltham, Massachusetts, 240 p. A Study of the Effect on Oysters of Crude Oil Loss From a Wild Well1 J. G. MACKIN2 Department o/ Oceanography and Meterowgy, Agricultura[ and Mechanical College o/ Texas, College Station, Texas and A. K. SPARKS College o/ Fisheries, University o/ Washington, Seattle, Washington Abstract An oil well went out of control, caught fire, and spilled oíl for two weeks in the Louisiana marshes in 1956. A series of stations was established with oyster trays and growth panels at varying distances. Measurements were made in the ensuing two years. Mortalities of oysters in the area were primarily associated with incidence of infection by the fungus Dermocystidium marinum typical of Louisiana and were not related to distance from the well. Disease incidence, oyster set, growth, associated organisms on the reefs, and oyster conditions were usual for the Louisiana area and apparently not affected by the spillage. Oily laste in oyster meats could not be identified after two months. Table of Contents INTRODUCTION -----------------------------------------------------------------------------------------------····-···----···· 231 The Oil Loss Disappearance of the Oil DATA CoLLECTED, METHODS, AND STATIONS ----------------------------------------------------------------234 The Stations Construction of the Racks Oysters PRESENTATION OF THE DATA ---------------------------------------------------------------------------------------239 Mortality Causes of Mortality Growth of Oysters at the Various Stations Set and Growth of Young Oysters Numbers of Young Oysters at the Different Stations Index of Condition Animal Communities at the Stations D1scuss10N AND CoNCLUSIONs -----------------------------------------------------------------------------------257 AcKNOWLEDGMENTs -----------------------------------------------------------------------------------------·---259 LITERATURE CITED -----------------------------------------------------------------------------------------------·· ······ 259 1 Oceano3raphy and Meterology Series from the Department of Oceanography and Meterology, and A. and M. College of Texas. A report from Project 23E, Texas A. and M. Research Foundation, sponsored by Texaco lncorporated, Humble Oil and Refining Company, The California Company, Gulf Refining Company, Phillips Petroleum Company, and Shell Oil Company. 2 Now Department of Biology, Agricultura! and Mechanical College of Texas. A Study of the Efject on Oysters o/ Crude Oil Loss From a Wild Well 231 lntroduction THE ÜIL Loss On about November 17, 1956, an oil well, the Ernest Cockrell No. 40, drilled by Mecom Oil Company, went out of control, caught fire and spilled oil for a period of about two weeks. The exact period of the loss is not known to the authors. It is believed that the oil loss was probably the largest ever sustained in the oyster producing area of Louisiana. This accident provided an opportunity to set up a large scale experiment designed to determine whether or not such oíl might affect survival, growth, or setting of oysters under natural conditions. In the weeks that followed, stations were set up at which oyster growth and survival were studied and compared with control stations located outside of the spill area .This paper is a report of the results of these experimental comparisons. The well was located in the Freeport Sulphur canal a short distance to the north of the Grande Ecaille mine of the Freeport Sulphur Company ( map, Fig. 1). The oíl spread in ali directions, sorne moving north in the canal and thence through Rattlesnake Bayou into Grande Ecaille and east to Lake Washington. Sorne oil spread to the south­east into Billet Bay and contiguous waters. On November 30, the fire was extinguished and the well blew oil and water for severa] hours before being brought under control. Mr. Ed Schrader investigated the extent of the oil spread on December 6, 1956. On that date, a film of oil was found in the northeast half of Lake Grande Ecaille and in Rattlesnake Bayou. This was in the form of a heavy slick. Rattlesnake Bayou was covered by a film of oil for sorne distance east and oil along the shore was noted. Thick­ness of the film could not be measured but it was more than an iridescence. Freeport Sulphur canal had a heavy coating of oíl and the entire shoreline was saturated, par­ticularly along the west side, and to the south of the well location. In the Freeport Sulphur mine area and to the east into the dredged cut the oil was very heavy and in the greatest concentration recorded. In the north branch of Rattlesnake Bayou leading to Lake Washington, there was a heavy concentration of oil on the surface of the water. Oil was found in small amounts along the entire shore of Billet Bay in small coves. Traces of oíl were found on the west shore of Lake Washington, but none was observed on the east side. On December 11, a further check was made by Mr. Ed Schrader, chemist with the Grand lsle Laboratory of the Texas A & M Research Foundation. At this time a slick was observed as far west as Saturday Island in Barataria Bay, with scattered patches to the west and north of Saturday Island. Here the greatest concentration was between Big Island and Saturday Island, and was continuous eastward to the west entrance of Lake Grande Ecaille. In Grande Ecaille there were patches of tarry oíl but no continuous slick. There were additional patches in Bay Ronquille, with pockets along the shore, and oil streaks on the vegetation and on shells along the east shore were observed. Heaviest concentration of oil was encountered near the southwest entrance to Grande Ecaille, near its junction with Ronquille Pass. Along the south and east shores of Grande Ecaille was another heavy concentration, and a large tarry patch was contained in the cove adjacent to the Freeport Sulphur mine on the south and east sides of Grande Ecaille. LEGEND 1 -STATION 1 2 -STATION 2 3 -STATION 3 4 -STATION 4 5-6-STATIONS 5-6 7 -STATION 7 8 -FREEPOAT OYSTER 9 -MECOM WELL @ STATION A Study of the Efject on Oysters of Crude Oil Loss From a Wild Well 233 Oil in the Freeport Sulphur canal extended northeastward beyond the junction with Bayou Cheniere. Up to the junction with Bayou Cheniere there was much oil, but it thinned out to the northeast and disappeared about midway between Bayou Cheniere and the Grande Bayou crossing. On December 13, the junior author observed that the oil in Barataria Bay had disap­peared, and no oil was observed west of Grande Ecaille on that date except a light film near the west entrance. Rattlesnake Bayou was also clear, but there was considerable oil on the water and along the shorelines of the Freeport Sulphur canal. To the east, oil was observed in the pass between Billet Bay and Lake Washington, along the shorelines, and in marsh vegetation. On December 26, 1956, the authors visited the area and, with Mr. Fred Deiler of the Freeport Sulphur Company, inspected the local area from Billet Bay into the dredged cut to the east of the Freeport Sulphur Company. No oil was observed in Billet Bay, but there was much oil in the dredged cut along the shores, but no more than light slicks over the surface. However, in tonging oysters on the Freeport Sulphur planted bed in the cut, oil was dislodged from the bottom and floated to the surface in considerable amounts. As late as February 5, 1957, oil could still be stirred from the bottom of this bed. Thus, the oysters used in stocking the experimental stations for this study were subjected to oil from the latter part of November, 1956, to February 5, 1957. It is not known just when oíl from the burning well reached the bed after November 17, but the exposure to oíl was certainly for more than two months. Tonging oysters from the Freeport Sulphur Company bed in Billet Bay on Decem­ber 26 failed to produce slicks. No bottom oil was observed outside of the immediate vicinity of the well and in the dredged cut, but it is assumed that around the margins of the bays sorne oil was absorbed on the mud. In assessing the extent of the oil loss, there is no way to determine how much oil escaped. Ali light fractions must have been burned when the well was on fire and much more evaporated. Thus most of the lost oíl was artificially "weathered" except in the short period of severa! hours after the fire was extinguished, but during which the oil flowed unhindered. In no case were the authors able to measure amounts of oil in any area with exactness, or to make exact estimates of thickness of oil film. During the six months of the study, the west end of Rattlesnake Bayou was observed to have almost continuous oil slicks. These liad no relation to the original oil loss but carne from the intense area of oil de·.'elopment in the end of the bayou. While this oil apparently was not connected with the Mecom well, it has a part in the study, simply because it was there, and close to our experimental Station 2. Station 2, located just to the north of the junction of Rattlesnake Bayou with Lake Grande Ecaille, was almost continuously subjected to light slicks for the duration of the study. It thus became a master experimental station. Station 2 also inadvertently became an experimental station in another sense. In the latter part of February, a canal was cut by Humble Oil and Refining Company just to the west of the racks. Oysters had already be~n placed at this station, although the formal checks had not begun. No effect from turbidity produced by this dredging could be observed. No silting of the oysters occurred. DrsAPPEARANCE OF THE ÜIL Oil disappeared very rapidly from the surface of the water in the bays and bayous, but occasional slicks which appeared to come from pocketings in the marsh and along­ 234 A Study of the Efject on Oysters of Crude Oil Loss From a Wild Well shore were seen to the end of December, 1956. Thereafter discolorations on the marsh plants and on shells along the shore gradually faded. By the time the actual data-taking began in early March, 1957, physical appearances were normal except in the immediate vicinity of the well and in the dredged cut of the Freeport Sulphur Company. The floating oíl was flushed to the Gulf, the major part probably passing through Bay Ronquille and Bay Long and out through Quatre Bayou Pass into the Gulf. A minor part probably was discharged through Chaland Pass, and it ís possible that sorne oíl slicks went through Pass Abel. However, no slicks were ever observed in Lower Barataria Bay, although frequent trips were made along the southern and eastern shores. It is believed that the oíl observed in northeastern Barataria Bay was discharged through Cat Bay and thence through Quatre Bayou Pass. Much oíl was evaporated as evidenced by the weathered appearance of the floating patches which were observed. Remaining oíl was reduced by bacteria! oxidation. Prokop (1950) has studied bac­teria! decomposition of petroleum and has shown that oíl cannot be retained by muds for long periods of time. Brown (1950) has also studied the bacteria! reduction of crude petroleum and Brown, Van Horn, and Reid (1950) demonstrated that micro­organisms in Louisiana muds destroy a large number of the compounds of crude petroleum. ZoBell (1949b) also measured the rate at which oíl is oxidized by bacteria, and he furthermore (1949a) showed that bacteria capable of destroying oil exist in Louisiana hay muds. The oíl oxidizing bacteria were found only in small numbers, but increase rapidly to large numbers under conditions of contamination with crude oil. They were shown to be widely distributed, in bottom muds of Louisiana bays. Data Collected, Methods, and Stations The data taken in this study include the following: ( 1) Measurements of the total mortality of oysters were made at severa! stations for the period of the study, and measurement of the rates of mortality were made during successive periods. (2) Analyses of the effects of the fungus disease Dermocystidium marinum in pro­duction of mortality of the oysters were based on diagnosis by the culture method de­vised by Ray ( 1952a, 1952b). A total of more than 1000 gapers and 1878 live oysters was cultured during the study. (3) Study of severa! other minor agencies producing mortality was also made. (4) "Condition" in control and experimental oysters was measured, using the coefficient-of-fitness method. (5) Studies were made of the macroscopic fauna of the trays, comparing control and experimental stations and the faunas of all stations with normal north-Gulf faunas as described by Hedgpeth (1953) and Gunter (1955). THE STATJONS Seven stations were set up; Stations 1through4 were designated experimental stations because they were in the area of heavy oil contamination. Stations 5 through 7 were placed at a distance from the contaminated area in lower Barataria Bay and were designated control stations. Stations 5 and 7 were stocked with oysters which had been A Study of the Efject on Oysters of Crude Oil Loss From a Wüd Well 235 subjected to oil, then removed to the uncontaminated control area. Station 6 was stocked with oysters which had never been in contact with oil. Ali stations were constructed in the last two weeks in February, 1957. Oysters were placed at the stations in the period of the last week in February and the first week in March. The last culling mortalities were removed on March 12 and the study began on March 13, 1957. The stations of the experimental group were in a region where salinity is "high," varying generally from about 10 ppt to about 27 ppt. At the three control stations in lower Barataria Bay the salinity range was from about one ppt to 35 ppt, a greater range but about the same median as that at the experimental stations. Station 1 was located in Billet Bay (Fig. 1) a considerable distance from the shore in any direction. Water depth at Station 1 was about three to four feet and the bottom was fairly stiff mud. The station was in an area of intense oyster production of probably an above average type for Louisiana. Station 2 was in Lake Grande Ecaille just to the north of the junction of Rattlesnake Bayou. 1t was in an area of intense oil activity. Fig. 2 shows the rack and in the near FrG. 2. Photograph showing the location of Station 2, an experimental station, in the northeast part of Grande Ecaille at the mouth of Rattlesnake Bayou. A christmas tree and drilling well of the Humble Oil and Refining Company are shown in the near background. foreground to the left is a completed well and to the right a drilling well of the Humble Oil and Refining Company. Drilling at this location was in progress during most of the period of the study. Station 3 was located on the south shore of Lake Grande Ecaille in about three feet of water. Heavy oil from the Mecom well was pocketed along the south and east shores of Grande Ecaille. Station 4 was located in the dredged area to the east of the Freeport Sulphur Company mine. lt was fairly close to shore, but in comparatively deep water. Ali other stations 236 A Study of the Efject on Oysters of Crude Oil Loss From a Wild Well were in three to four feet of water, but here the depth was about eight feet. The con· struction of this station differed from that of the others. The entire structure was iron or steel and the " baskets" were of heavy iron meshwork supported with an iron frame. These trays were hauled to the top of the platform by means of a hand-operated chain hoist. When submerged, each tray was covered with a rectangular iron meshwork on a frame. Stations 5 and 6 were placed within 20 to 25 feet of each other. One of these (Station 6) was the "master control" and was placed as near as practica! to Station 5 ( Fig. 3). Frc. 3. Photograph of the racks of Stations 5 and 6, two of the control stations. The marsh beyond is Grande Terre east of the entrance to Sugar House Bayou. The area is referred to as Sugar House Ben d. They were in the area called "Sugar House Bend," near the north shore of Grand Terre Island, in the southern part of Barataria Bay. The bottom at Stations 5 and 6 was packed mud-sand mixture, and the depth was three to four feet. This location was chosen because there are available extensive data on mortalities from studies carried out in previous years. Station 7 was placed in Sugar House Bayou, which transects Grand Terre in a general northwest-southeast direction. Originally this "bayou" was a part of the ex­tensive drainage system when attempts were made to grow sugar cane on Grand Terre. Station 7 differs from other stations in that it is in an area where natural populations of oysters grow in small reefs along the edge of the bayou. Natural populations of oysters do not grow in the area around the other stations, where the capacity for maintenance has long since been lost. Station 7 differs in one other respect from the other locations. In summer, water temperature is often very high during ebb tides, sometimes reaching 4.0ºC (Mackin and Cauthron, 1953). CoNSTRUCTION oF THE "RAcKs" Wooden structures, made of creosoted "two by fours," were used to support the trays of oysters. They were joined together with galvanized bolts. The lower ends of the A Study of the EIJ.ect on Oysters of Crude Oil Loss From a Wild Well 237 uprights were sharply pointed and when the racks were installed the pointed ends were forced into the mud bottom until the cross »tringers on which the trays rested were on the mud. Cat walk frames were built alongside the supporting frames for the trays, and joined with cross braces on which the cat walk planks were placed. These units are very strong; those used in this study passed through hurricanes Bertha and Audrey without damage and without losing an oyster. The use of tarred trays for raising oysters is standard procedure in different parts of the world. The trays are usually supported on creosoted wood structures. For a description of a highly successful operation using the identical trays used in this study, see Anonymous (1940). Also see Nelson (1934) and Hewatt and Andrews (1954) . Trays were prevented from washing off the stringers by heavy wire bridles which were attached to the upper stringers. When the trays were examined they were lifted to the surface with the bridles. Ali trays were sealed by a second inverted tray which was hinged to the lower tray and wired in place before leaving at each visit. One of the trays is shown in Fig. 4. l.. F1G. 4. Trays containing oysters at Sugar House Bend. Note the galvanized rat wire lining used to exclude predators, and the board partition which was riddled by shipworms. Mr. Thatcher (left of the observer) and Mr. Landry check for gapers. Note the cat walks on which they stand. These boards were removed after each Yisit to discourage tampering. ÜYSTERS Oysters used for the four experimental stations and two of the control stations were taken from the Freeport Sulphur Bed in the dredged cut just to the east of the Grande Ecaille mine. The location of this bed is shown on the map, Fig. l. The oysters ranged from seed size to quite large oysters ( see size distribution diagram, Fig. 5). At the time they were tonged and dredged for distribution to the stations, they were growing well, were fat, and well shaped. As stated, this area was heavily contaminated with oil, and the mud still contained suflicient oil to form slicks when the oysters were taken up. They had been subjected to this condition for more than two months when removed to the stations. 238 A Study o/ the Efject on Oysters o/ Crude Oil Loss From a Wild Well w .050 0.5 a. 10 150 M A M A s SHELL LENGTH -MM -OEA TH RATE -DEATH RATE ---D€ATH RATE TO O. MARINUM ---DEATH RATE 1"0 0. MARINUM -·--·WEIG HT ED INCIDENCE .250 2.5 -----WEIGHTED INCIDEN([ w 2.0~ .200 2.0~6 .200 o w 'Z ::¡ Q ~ u . p--·-o--­ ~ .150 1.5~ ,.,..;:&.,----', ~-1 50 1.5 ~ .' / ~ / B ·-----o·'/ \ ---. ~ 8 1.0~ __ ..-p---.ef \ ·u :i: .100 1.0 ~ ~ .100 <,'? cr / 'o_ ~ ~ < w w '/ ---o w ;: FIG. 8 o .050 0.5;:: / FIG. 7 º .oso os M A A M A M J A s MON THS MONTHS F1c. 5. Size distribution diagram for oysters in a sample from the Freeport Sulphur Company plan ting in the dredged cut. This histogram shows the sizes of oysters used in stocking Stations 1, 2, 3, 4, 5 and 7, from which the year classes and maximum age of the oysters present were determined. F1c. 6. Death rates from ali causes, weighted incidence of Dermocystidium marinum, and death rates from this fungus disease at Station 1, March to September, 1957. F1c. 7. Death rates from ali causes, weighted incidence of Dermocystidium marinum, and death rates from this fungus disease at Station 2, March to September, 1957. F1c. 8. Death rates from ali causes, weighted incidence of Dermocystidium marinum, and death rates from this fungus disease at Station 3, March to September, 1957. Oysters used for the master control station were obtained from an oysterman in lower Barataria Bay. These had recently been transplanted from a low salinity area above Timbalier Bay just prior to the time they were obtained, a fact not known at the time they were purchased. They had a very low incidence of Dermocystidium marinum infection compared with the experimental oysters. This accident presented an oppor­tunity to incorporate into the study a test of the theory that subjection to oil may enhance the effect of D. marinum, and that incidence of infection by the fungus is increased by the presence of petroleum_ The possibility that subjection to oil is necessary for production of D. marinum mortalities or development of epidemic disease has been tested with negative results (Mackin, 1950). However, no field tests have hitherto been carried out. We were, there­fore, presented with an ideal situation, namely that of being able to compare develop- z Q .02~ 25 1­ < ..J ::> a. 20 .2 00 o a. d::; ..J < 15 w-150 1­ 1­ o 1­ < Q'. 1­ I.100 z 10 w 1­ u ~ Q'. o -DEATH RATE -·-DEATH RATE TO O. MARINUM 2.5 ---· · WEIGHTED INCIDENC E 2.<:fiw w e u 1.5~ o w 1.0~ <.) w ;: A Study of the Efject on Oysters of Crude Oil Loss From a Wild Well 239 ment of epidemic disease in oysters which had neither been subjected to oíl nor to fungus disease, with oysters which had had the maximum field dosage of crude petroleum, carne from an endemic area, and were infected at the beginning of the study. Each of the seven stations was provided with trays which held 1000 oysters. At each station there were 300 oysters used for determination of total mortalities. This group was used for nothing else, except that gapers recovered were subjected to the Ray culture technique for determination of incidence and intensity of infection with D. marinum. Since only a small part of the meat was used in culturing, the remainder of the oyster was fixed in Zenker's fluid, when not too badly disintegrated, in order to allow for studies of other diseases should such appear. · Six hundred oysters at each station were reserved for analysis of intensity of disease caused by D. marinum in the live oysters. Samples of 50 oysters, 25 of them relatively large and 25 small, were withdrawn from this group each month for the measurement. Ali gapers from the group were also cultured and fixed to provide further checks on fungus disease in dying oysters. The group also contributed to the determination of mortality leve! from month to month. The third group of oysters, numbering 100, was reserved for condition studies, and 10 were withdrawn for this purpose each month. Toward the end of the study the group dropped so low in number that the live oysters used for diagnosis of D. marinum were used for condition studies after excising the small piece of tissue used for the culture. No checks for condition were made at the beginning of the study. Condition was measured by the "index of condition" method ( dry weight of meats in grams per shell capacity in ce, times 100) . The volume of the shell cavity was determined by the dis­placement method and the meats were dried at lOO º C to constant weight in a drying oven. A chainomatic balance was employed ih the weighing. Presentation of the Data MORTALITY Mortality rates for the region as shown by age analysis. Prior to the beginning of these studies a sample was taken from the bed of the Freeport Sulphur Company in the dredged cut (Fig. 1). This sample was taken on January 23, 1957, and is representative of the oysters used in these studies ( excepting those at Station 6) . The length of the right valve of the shell of each oyster of the sample was measured, and the size frequency plotted to provide data with which to calculate growth during the period of the study. An estímate of the annual mortality to which these oysters are subject may be made by examination of the size distribution diagram. The method consists of identification of the maximum number of year classes in tht population, using the modes in the size distribution diagram and basic knowledge of growth rates gained from previous studies. The current year class may be separated from ali older year classes on the basis of color and general appearance of the shell. This was done at the time of measurement of the oysters. The size distribution diagram is shown in Fig. 5. The oldest oysters in the popula· tion probably set in the spring and summer of 1953, certainly not earlier than late April or May of that year. On January 23, 1957, they were, therefore, about 31;2 years old. Only a remnant of that year class remained alive, since it made up only about two 240 A Study of the Efject on Oysters of Crude Oil Loss From a Wild Well percent of the oysters represented in the diagram. An average annual mortality of at least 60 percent is indicated, the figure necessary to reduce a population to such a low level in 3112 years time. The steps in application of the method were as follows. First, it was necessary to know the size of oysters which are in their third year. This information was obtained from actual measurement of growth of oysters in previous ·studies and the sizes which they may attain. Reference is made to two representative studies. The first study was reported by Menzel (1950). He found that oysters at Bayou Bas Bleu grew from setting (in May) to a mean shell length of 58 mm (about 21/3 inches) in one year. Oysters one year old grew in their second year from about 54 mm to about 84 mm ( about 3112 inches). Oysters in their third year grew from 86 to 101 mm, at which time they were almost exactly 4 inches long (100 mm). All figures represent means. At the end of three and one-half years the oysters in our sample, at the rate found by Menzel, should have grown to a mean size of 112 to 125 mm. In the second study Dawson ( 1955) got results similar to those of Menzel but did not check growth in the first six months. Ingle and Dawson (1952) found a higher rate of growth in Apalachi­cola Bay, Florida, but pointed out that their data indicated that in this hay growth of oysters was superior to any other area studied in the United States. An examination of the size distribution diagram (Fig. 5) shows that only a few oysters of the sample from the dredged cut bed of the Freeport Sulphur Company exceeded 100 mm in length and none attained 140 mm in length. Thus from the sizes there were few, if any, oysters older than 3112 years in the sample. This conclusion is supported by study of the diagram itself. Each year class, if it could be separated from the whole would make a more or less symmetrical diagram (the "normal" curve). The 1956 year class was separated from the older oysters when measuring on the basis of shell color and form (Fig. 5), and there can be no question about the age of that group, which contained oysters four to eight months old. The oysters in the block to the right of the 1956 group must represent the 1955 class, which was up to 20 months old. There­after no definite division exists because of reduction of numbers by deaths and fusion of the modes by reason of slower growth in the second and third years. However, the marked asymmetry of the right hand limb of the histogram indicates that at least one other year-class (1954) is represented (2 to 21/2 year old), and the few straggling oysters over four inches in length indicate that these probably were between three and four years old. Certainly the oldest year class represented is less than 5 percent of the number of the youngest year class: it is reasonable, therefore, to assume that this group had sustained more than 95 percent mortality since setting in 1953. Table 1 indicates the period required to reduce a population to less than 5 percent of its original size with various mean percentages of annual mortality. At 10 percent mortality, more than 28 years would be required to reduce a population to less than 5 percent of its original size. With a known longevity of three and one-half years the mean annual mortality rate would be about 60 percent. At the beginning of the study it was, therefore, indicated that if the time of the investi· gation carried over a considerable part of the summer, the mortality should average above 50 percent. Past studies in Lake Grande Ecaille (Mackin and Wray, 1950) showed that in the period from March to September the mortality was 63 percent and at Sugar House Bend, it was 74 percent in the same period. A Study of the Efject on Oysters o/ Crude Oíl Loss From a Wíld W ell 241 TABLE 1 Approximate time required to reduce a year-class population of oysters to less than five percent of its original size at different mean annual rates of mortality Mean annual Approximale nurnber of years lo mortality rale (percenl) reduce lo Iess than five percent 10 20 30 40 50 60 ' 70 80 90 28 to 29 about 13 8 to 9 about 6 4 to 5 3 to 4 2 to 3 nearly 2 l plus Mortalíty from the date of oíl loss to the samplíng date. The mortality rate derived from this method applied to oysters in the area from which the seed for planting the bed were taken, since too little time had elapsed after planting for the environment of the dredged cut to affect mortality rate. Indications were that very little mortality had occurred in the last two or three months befare the beginning of the study. Recognizing that numbers of boxes (hinged valves) do not indicate mortality rate (Menzel and Hopkins, 1952), the condition of the boxes will show whether or not a recent rapid mortality has occurred, if that mortality was significant and concentrated in a rela­tively short period of time. The sample taken on January 23 had less than five percent boxes, none of which were "fresh", i.e., not fouled. Even if all of the boxes had been "new" the mortality rate since the oil loss would have been negligible. Cumulative mortality of oysters at the control and experimental stations, March 3, to September 4, 1957. Table 2 shows the total mortality for the seven stations used in this TABLE 2 Mortality of oysters in percent at the experimental and control stations for the entire period of the study, March 3 to September 4, 1957. Data are from the oysters in the "mortality" trays only, 300 at each station, and from thc total population beginning with 1000 oysters and calculated from the mortality rates in different periods as shown in Table 4 Station Total mortality (using 1000 oysters) percent Area No. In oil area 1 '2 3 4 Control area 5 6 7 65.1 59.0 61.2 30.4 48.0 80.7 63.5 Means 53.9 64.l Total morlality ( 300 oysters) percent 60.7 52.7 65.0 28.3 42.3 79.7 55.0 Means 5.U 59.0 study. With the exception of Stations 4 and 6, the mortality rates were about as expected. Station 4 had distinctly less mortality than expected. However, the average (51.7 per­cent) for the experimental stations and the average (59.0 percent) for the controls were sufficiently in agreement that it appears that the differences were not significant. An overall difference of seven percent is slight considering that between experimental 242 A Study of the Efject on Oysters of Crude Oíl Loss From a Wild Welí stations there was a difference in total mortality of about 37 percent (Stations 3 and 4), a difference which was matched by that between two control stations (5 and 6) of 37 percent. Mortality rates in the difjerent periods ( months} of the study. Total mortality figures do not show changing rates of mortality. AII stations began with a relatively low rate of mortality which generally held through March and April (Figs. 6 to 12). Thereafter, .250 .200 o -z W .150 .... < a: I .100 f­< w o .050 .350 .300 .250 0.200 z w .1 50 .... < a: I .100 .... < w o .050 STATION 4 f1G 9 2.s .250 LEGEND f IGS 9 TO 12: w 2 .0~ -DEATH RATE .200 w e ----·WEICHTED INCIDENCE ,o u , 1.5 ~ --OEATH RATE TO D. MARINU~O", , .1 50 ,, o w JY ,o__ LO i: , .100 , "w o· ·o' ~ / 0 .5 3: 050 . 3.5 3.0 .3 00 2 .5 .250 g w u 2.0 z :? .200 e w :/ 1.5 .150 u ~ .i o w :¡ .... 1.0 I .1 00 ~ ) w ,'f 3: flG. 11 0 .5 .050 .z:-:-.:..i -_:.:.. STAT ION ~ flG. 10 2.5 o.. - / 'o 2.0 Ji / /\ / . , 1.5 / . \ / ' ¡:I , ~ , , J 1.0 0----.T/ / ,o" 0.5 / ,,. .rY . Ecaille March 1000 0.25 April 986 3.875 0.69 0.81 May 888 3.36 o:n 1.09 June 717 3.75 0.94 1.31 July 573 4.19 1.32 1.90 August 407 4.27 1.69 2.17 September 281 5.00 0.92 1.62 Station 4, Dredged Cut March 1000 1.21 April 971 '2.50 0.69 0.71 May 893 2.88 0.90 1.05 June 783 3.88 0.71 0.8.3 July 696 3.06 0.89 1.18 August 574 4.'20 1.22 1.40 September 484 4.19 0.87 1.80 Stalion 5, Sugar House Bend March 1000 2.00 April 982 3.17 0.89 0.92 May 907 3.00 0.69 0.82 June 795 3.76 1.01 1.26 July 664 3.65 1.50 1.79 August 524 4.50 1.83 2.38 September 376 4.50 1.82 2.06 Station 6, Sugar House Bend March 1000 0.00 April 991 0.26 0.06 0.07 May 892 0.31 0.10 0.14 June 645 2.05 0.26 0.37 July 555 4c20 1.62 2.27 August 366 4.96 2.41 3.64 September 140 5.00 2.82 3.58 Station 7, Sugar House Bayou March 1000 2.00 April 986 3.93 0.90 1.04 May 880 4.38 1.04 1.44 June 715 4.62 1 .50 1.84 July 587 4.67 1.97 2.31 August 463 4.84 1.41 2.57 September 256 1.50 1.78 1.74 *Weighted incidence combines incidence and inlensity o( disease to make a conveoienl scoring device. When a sample of oyslers is checked for disease, it is scored as follows: those oysters negaLive=O, Lhose very lightly infected= 0.5, light infec· Lions=LO, lighL Lo moderate infections= 2.0, moderate=3.0, moderale Lo heav)'·=4.0, heavy=S.O. The sum of Lhe seores is divided by the number of oyslers checked to give the weigbted incidence. t Becausc checks of the statíons were not exactly on the first day or last day of each month, the monthly periods are only approximately correcl. March and Seplember were shorl months. l Reduction in numhers of oysters sbown in this column were nol ali due lo deaths. Live oysters werc withdrawn monthly for condition studies and for disease analysis. 248 A Study of the Efject on Oysters of Crude Oil Loss From a Wi/,d Well fact that there were other differences between the two populations of oysters. The basic diff eren ces probably lie in two factors. These are as follows: (1) Since the oysters at Station 6 had not been subjected to wholesale infection by D. marinum prior to removal to lower Barataria Bay, the population was composed of a very high percentage of susceptibles. The mortality process, weeding out susceptibles, had been going on for sorne time in Station 5 oysters, shown by the high incidence of D. marinum in the sample taken in January (Table 3). This high rate of infection must have been a carry-over from the preceding fall and summer. Hence, the percentage of oysters highly susceptible to D. marinum must have been considerably lower at Station 5 (and ali other stations) than was the case at Station 6. Maxcy (1948) presented an excellent discussion of the effect of numbers of susceptible individuals in the develop­ment of epidemic disease in a corrimunity. He showed that the number of susceptibles in a population largely governs the development of epidemic waves. (2) lmmune reactions had already raised the capacity to resist development of severe disease in a high percentage of the oysters at Station 5, Over half of them were shown to be carrying infections in the winter and early spring, and additional oysters must have had the disease in the preceding summer and fall. Thus not only had the highly susceptible fraction of the population been eliminated by deaths, but, in a part of the remainder at least, individual immunity was increased through contact. At sorne stations the last month showed a decrease in case rates and death rates to fungus disease. This is believed to be due to elimination of large numbers of susceptibles during the preceding high mortality periods. At sorne stations the peak of the summer epidemic was not reached until September (Stations 1, 3, and 7) , and might have gone higher in October if observations had been continued. Hewatt and Andrews (1956) also found that oysters from an endemic area had a greater resistance to infection and a sharply lower death rate when artificially infected than L._____--E ~:L-----·l./-:.=-::·--.:-=-'-~7'~------,_¿~--­ !~ ~: \; ,/ ­ ,. >-------17,500 FEET ---------< Frc. 5. Depth transects of Lake Grande Ecaile, showing depths in 1934, 1948, and 1959. Data for the transects of 1934 and 1948 are from Lynch (1948a). "''<-"'­ ~+~!,.­ o'-9-,,.,.,,,. 'º,.....,.o // LAKE ECAILLE \\ " \1,, l 01 llTION~ ANO OIH 0\.INV 0A1 l S 01 Dll(nr.1 o llY tlU "llH 1 OIL o llU ININ\. co IN <> {,QllL 54"'1'llS 0Al(O r t811UMIY 20 O ZI, l Al\l \,11/INOl [{,lr.lllE 01SP0Sll10N 01 SPOIL it LE.6$CS 9H •HOnr.•. ~e· O' TIO( AllTlf"<••• llH'· "-"!:• t7 O'fST[lllhG COl'i!OUl>S 5"0W l)(PH< O' $0<"1 fl'I[ O•h!;<'1•L .U1Tffl(1•L ~((f 00! SToH &QIT(W Ol'i ARE:• CLA " EO 10 8( O•,..o.Gt~ These layers may be slowly covered with later deposits, and become buried more or less deeply. However, in areas where slow scour is taking place, winnowing may uncover successive layers of foram shells which are concentrated in and near the mud surfaces. Abnormally rapid deposit, such as was claimed in the case of leases 9861 and 9864 may precipitate suspended silts on the bottom so rapidly that foraminiferan accumula­tion would not be possible. Such rapidly deposited layers do not contain forams, nor do they contain shells of molluscs, large woody debris or any other particles too large and heavy to be moved by means of ordinary current. Figs. 16 and 17 show different types of foram shells. The spiral forms are most common, especially those with calcareous shells. These may contain small nodules. These are mostly metallic sulphide concretions. Spirals with chitinoid shells are common in muds in sluggish bayous, where the calcareous shells are absent. It seems probable that sorne highly reducing muds may destroy the calcareous shells. '.' !CHJ-.. f<~Y ¡'.:,1_,c;.~,$ ~i.l , ')~6 U!' f AKF: .JI'( 14, 95i' Forarns which produce the "sand grain" cases are cornrnon in low salinity areas, and are present in srnaller numbers in higher salinities. Sorne of these are roughly spiral and sorne are flattened and oblong. In Fig. 16 is shown one of the chitinoid forrns found cornrnonly in rnarsh ponds. These are so characteristic of the rnarshes that they rarely are found far frorn shore. They have been taken in great abundance in rnarshes where no ponds are presently found. There are severa! different species of these interesting forarns which look oddly like an insect wing under the rnicroscope. The oblong shell shown in Fig. 16 appears not to be confined to any single habitat, but is rnuch more abundant in bayous of low salinity than in open bays. Shell fragrnents frorn rnuds are shown in the photographs, Figs. 18 and 19. The shell in Fig. 18 is blackened with the sulphide characteristic of long-buried fragments of oyster shell. There are sorne interrnixed shells of other rnolluscs, which retain a white color irrespective of length of time of burial. In Fig. 19 the shell is nearly all white, F1G. 18. Oyster shell and other shell from the Franks-Vu.jnovich leases. ( Left 1 FIG. 19. Shell fragments from acore in Lake Grande Ecaille. (Right) showing against a black background. The plant debris showing over the white back­ground is characteristic of marsh muds. Origins of silt may sometimes be detected on the basis of reduction of weight of muds with ignition. Loss on ignition does not give an accurate measurement of organic content of the muds, but the measurement is comparative between samples. Since most carbon compounds in the muds are derived from marsh plants, highest concentrations are marginal in the bays and decrease toward the centers (see Mackin and Hopkins, 1961, Section 5). Establishment of a decrease in values of loss by ignition, from the shore to offshore areas, would indicate that silts on leases 9861 and 9864 were largely derived from disintegrating and slumping marsh shorelines. When leases 9861 and 9864 were first studied it was found that they were, for the most part, quite silty and soft. Muds were found by probing to be almost mushy in places, while others were quite hard and with the consistency of a shell reef. No natural reef was found. Ali gradations of depth of soft silt were found up to more than one foot and ali gradations of consistency from very hard to very soft were observed. The prob­lem resolved itself into determining whether or not the Humble Company dredging operations were responsible for the soft silts found on sorne portions of the bed or whether the observed silts were the result of other factors. CoRES FRoM THE MuDs AccuMULATING IN THE CANAL DREDGED TO WELLS 28 AND 29 It was indicated above that the access canal to wells 28 and 29 was dredged within the period from November, 1954 to February, 1955, when it was claimed that leases 9861 and 9864 we~e silted. It was also. tlie closest canal to leases 9861 and 9864. Wells 28 and 29 were dry holes and the canal was abandoned shortly after the drilling was completed. When the inves~igatiqn of the claims began about a year after the dredging operation, the canal had silte4. up level with the surrounding bottom. Abandoned canals in low-current-velocity ~feas 0always silt up. While canals are in use, propeller wash may prevent silting to 'só~e extent. The silt which was deposited in the canal was used to determine the characteristics oí silts carried by currents in Lake Grande Ecaille. The numbers of foraminiferan shells and molluscan shell fragments, the sizes of woody fragments, and the loss oí weight on ignition, were determined for cores taken in the canal, located approximately on the center line between the two margins. Engineers of the Humble Oil and Refining Com­pany surveyed the canal and the locations of the cores were plotted (Fig. 6). Field examination of preliminary cores showed that they were composed of a uniform silt without any macroscopically visible shell, sand, or woody debris except at the bottom where the coring tube penetrated the original bottom. Two cores were taken at each location. These were analyzed microscopically. This analysis showed the following: ( 1) Foraminifera were very rare. None were found in the silt in one core, only one in another, and ten in the third. All of these foram shells were very small, ali being less than 1/ 80 inch in diameter. (2) Shell fragments were also rare. Only one was found which was classed as large ( about one-half inch). All others ( 12 total) were very fine fragments and all were ftattened ftakes. One core had no shell at all. (3) Woody debris was comparatively small in amount, and was composed of very fine fragments. In only one core were woody fragments of any size found and there were only a few of these. However, examination of the silt which passed through ali sieves showed that there was very fine plant debris in considerable quantity. In none of the cores were there layers of peaty materials such as is found in undisturbed bottom. ( 4) Sand was present only in the fine sizes, no medium or coarse sand being present. Sand here means silica sand, but the sizes are according to the conventional geological classification. These data are summarized in Table 9. Spoil from the original canal was spread over the bottom, the closest part of the direct depositing area being 50 feet from the canal. Since the canal itself was 65 feet wide, the cores were about 32.5 feet from the margins of the canal. It was obvious that water transport of forams, shell, and large woody debris was extremely limited even at the short distance involved. lt is believed that the forams developed in the mudas it accumu­lated but there could have been limited transport. The canal was cut into the bottom to a depth of approximately four feet so that roughly the silt was deposited in the aban­doned canal at a rate of about four inches per month, if the rate was uniform through TABLI:. 9 Numbers of foraminiferan shells, and fragments of molluscan shell from three cores in water-borne silt fill in abandoned canal to wells '28 and 29 No. of íorams No. of shell fragments Core no. per inch of core per incb of core 16 0.3 1.7 14 o.o 1.8 15 5.0 o.o the year of deposit. The data indicate that forams may not live to reach mature size if the mean rate of deposit is about four inches per month. Muds from the cores taken in the canal to wells 28 and 29 were dried to constant weight and then ignited in a muffie furnace. The results are presented in Table 10. The data show that the range of values is comparatively small in ten samples, the mean amount of 14.4 percent loss of weight is only moderate, and there is no difference in the ignitable materials in the top six inches and in mud more than six inches below the surface. These values will be compared with others in the table later. CORES FROM THE AREA NüRTHEAST OF THE DREDGING Two cores were taken on February 20, 1956, in the area to the northeast of the canal to wells 28 and 29. These locations are shown on the map, Fig. 6. One (No. 397) was quite close to one of the more northerly canals, near well K, and another (No. 738) was just to the northeast of well 29. Each of these was 150 to 175 feet from the respective closest canals. Neither was in a spoil area. It was believed that cores taken in this area would show silting if any part of Lake Grande Ecaille had been affected by water-borne silt, or precipitation of silt, caused by the dredging operations. Macroscopic study of these cores showed that there was about one inch of a Jight­colored soft mud on the surface. Below that, there were numerous shell fragments down to about six inches below the surface. This part of the cores was moderately compact. Below the six-inch level, the cores were composed of compacted clay-like mud and there were peaty layers in the bottom of the longest core. This one was twenty-one inches long. Shell was abundant in the bottom six inches of this core. Microscopic study showed that the soft mud in the surface inch of both of these cores had 100 to 200 large forams and a small amount of shelL There was no indication that silting had occurred in the area where they were taken. lt is certain that the bottom was normal below the top inch of soft materials. Since one-fourth to one inch of a soft flocculent material is common in cores from hay bottoms, it is probable that there had been no deposition even in the immediate vicinity of the canals. The presence of con­siderable numbers of forams and sorne shell in the top inch indicates that the difference in color of the top inch was due to presence of oxygen which prevents the formation of TABLE 10 Loss of weight on ignition by various muds. Values are percentages of the dry weigbt of the samples Mean loss Range of loss of Disianee Location of samples No. of samples of weighl, percent weight in these samples. percenl from spoil deposit area Si!t trapped in canal after abandon­ment; top 6 inches of silt 4 14.4 11.9 to 17.4 50 feet Silt trapped in canal after abandon­ment; below 6 inches From spoil area: in top 6 inches 6 12 14.4 8.3 12.2 to 18.3 4.0to12.3 50 feet Zero From spoil area: below 6 inches (below spoil) Bay bottom: top 6 inches · Bay bottom: below 6 inches 7 15 4 12.4 10.3 27.7 7.0 to 18.3 6.5 to 21.9 16.7 to 40.l Zero 1500 to ·2500 feet 1500 to 2500 feet On leases of Franks-Vujnovich: top 6 inches 55 16.3 7.1 to38.0 More than 5000 feet On leases of Franks-Vujnovich: below 6 inches 26 33.4 6.4 to 67.2 More than 5000 feet metallic sulphides. Microscopic study of the cores at two to three inches below the surface showed the presence of large amounts of molluscan shell and up to severa! thousand foram shells per inch of core. At four to five inches the number of forams was less, indi­cating that there had been a concentration of forams in the muds near the surface of the core, possibly accomplished by a removal of fine silt by turbulence of wave action. Cores· were taken in the area between the nearest canal and leases 9861 and 9864. The locations of these cores are shown on the map, Fig. 6. There were six of these in an approximately straight line, about midway between the canal to wells 28 and 29 and the leases. The location of the line of cores was selected where the current velocity was least, as indicated by the great width of the hay at that point. Since tidal movement on ebb tide, as indicated previously, runs from northeast to southwest, when not diverted by wind, the cross-sectional width of the hay at the line of cores was more than two miles and the cross-sectional area close to 50,000 square feet. The flow from Rattlesnake Bayou into the hay (see Table 2) was measured by Lynch at about a maximum of 492.5 million cubic feet per 24 hour period providing a tidal current of less than 0.1 knot at the location of these cores. Wind drift currents may be slightly more than this ordinarily. If any part of the hay is subject to more deposition by reason of slow current, this area of bottom is most likely to accumulate either drifting spoil or silt. Any shoreward area is more likely to be scoured from wave wash than is the deep area selected, a half mile from the nearest shore. These six cores were carefully studied both macroscopically and microscopically for evidence of recent silting. In Fig. 20 is a composite diagram of the six cores, giving both microscopic features and macroscopic characteristics. In Table 11 is a summary of the microscopic analyses made. The cores showed that no silt had accumulated on the bottom in that area. There was nothing to indicate that the bottom was abnormal in any way. There was about a one­ half-inch layer of loose aerated mud at the surface which contained shell and numerous COMPOSITE O!AGRAM OF CORES TAKEN OF TME AREA SETWEEN fRANKS -VUJNOVIOi LEASES to.NO TrELL OECREASE FROM 2" TO 15" OOWN, MORE P\..A"IT :.; Tl"llS IS A PEAT LAYE.A WITH H(.l.VY COl>•<>< u•s.u U A , ..... Cl!OH 0t l..C O>Sf"-'Al fllOW $Hll•E Fic. 23. Amounts of organic materials in muds on the Franks-Vujnovich leases as a function of distance from shore. TABLE 12 Organic material in peat deposits: samples from parts of cores obviously made up of undisturbed plant debris around the shores of Lake Grande Ecaille Core level Organíc distance from conteot; Core no. Location the top (inches) percent 16+2-21-56 36+ '2-21-56 Vujnovich lease Pond on Franks' Island 5-6 8-9 67.2 78.2 25+2-21-56 Vujnovich lease 3--4 62.9 26+2-21-56 33+2-21-56 Vujnovich lease Lease 10612 N. Grande Ecaille 5-6 6-7 63.6 59.5 34+2­21­56 Lease 10612 11-12 68.3 35+2­21-56 Lease 10612 6-7 70.1 1+3-23-56 Franks' lsland in ma~sh 1-2 '26.8 1+3­23-56 Franks' Island in marsh 6-7 70.1 1+3-23-56 Franks' Island in marsh 10-11 35.4 1+2-17-56 N. Grande Ecaille 12-13 58.6 4+'2-17-56 N. Grande Ecaille 9-10 36.8 8+2-17-56 N. Grande Ecaille 11-12 59.4 Data on shell in the mud o/ the cores. Molluscan shell fragments were found in ali silts of marine origin on the leases. Literally every core showed on macroscopic exami­nation that shell, either in the form of entire valves or fragments, was distributed throughout the mud from the surface downward. Much of this shell was derived from Rangúz, Tellina, hooked mussel, oyster or barnacles. Less abundantly other bivalves were represented. Sorne shell recognizable as belonging to the conch (Thais) was found, and borings by predaceous snails were common in Rangia shell. Much of this shell material was in quite large pieces but ranged in size down to very fine fragments. Figs. 18 and 19 show samples from the coarsest sieves (1/10 and 1/20 inch mesh) . The scale at the left of the dish is one inch. lt is not possible that the shell found in the mud on leases 9861 and 9864 was carried by the weak current of Lake Grande Ecaille over the intervening mile of bottom from the canals dredged by Humble Oil and Refining Company. Since there is no method of mixing the shell with silt except by natural accretion over a period of years as the silt accumulated, the presence of this shell showed that the silts were not a result of the dredgings. The shell in the muds on leases 9861 and 9864 was carefully compared with that (1) in the silt accumulated in the canal to wells 28 and 29, (2) in the spoil dredged from that canal, and ( 3) from the intervening hay bottom. The silt in the canal contained only rare, very small bits (one exception of a fairly large fragment) of shell unrecog­nizable as to type, except that it was not oyster shell. The spoil removed from this canal had a high proportion of snail shells, including the above mentioned Zebra shell (Fig. 21) and no oyster shell. The shell from the intervening hay bottom was like that of the muds on the leases except that there was no shell of oysters, or of hooked mussels, bryozoa, or barnacles, which are commonly associated with oysters. Thus, even if it had been possible to transfer shell from the spoil to the leases, the difference in type of shell indicated that the fragments in the muds on the leases could not have come from the dredged canal. Data f rom foraminiferan tests. Foraminifera also were distributed throughout the muds on the leases. Numbers found and levels in the cores shown in Tables 13 and 14. In Fig. 24 is shown the mean increase in numbers from the shoreline outward. The increase in number offshore again indicated quite clearly that the origin of the silt& on the leases was the adjacent shoreline. The map, Fig. 15 gives the data on the depths of silt on the area claimed to have been damaged. lt will be seen that most of the area was either not silted at all or had only insignificant silt. However, the north and west sides were covered with three to ten inches of mud. But the cores showed that most of this deep silt was not on the artificial reef at all. The boundary of this reef is róughly shown in Fig. 15. Only on the west side was the shelled area covered with more than one or two inches of soft mud. lncidentally the cores also showed that there was much old eroded oyster shell overlying the Rangia shell, indicating that the artificial shell reef had been built years ago. No area where Rangia shell had been recently spread was encountered in the coring operation. Discussion of the data from the study of leases 9861 and 9864. The data accumulated in this study indicated that there was soft mud on the leases in certain places. But the data also showed that the silt had accumulated over a long period of years. The origin of sorne of the silt was indicated to be the disintegrating shoreline of the adjacent island (Franks' Island) and East lsland. Silt also was undoubtedly accumulated from the generally distributed suspended materials always in the water. The beds became a depositing area, after being for a long time a scour area, because of the general subsi­dence of the bottom common to the entire region, and the opening and gradual increase in size of the cut south of Franks' Island. The presence of considerable molluscan shell and the normal foraminiferan shell accumulation in the muds showed that the deposition took place over a period of years rather than in the few months (November, 1955 to February, 1956) as claimed. Of very considerable interest was the finding that the hay as a whole was not silted as shown by numerous corings along the shores and corings in the open hay. E ven those cores taken quite close to canals indicated no silting other than that from direct depo­sition of spoil. lt was indicated that the dredgings had changed nothing of a general ecological nature. No slowing of current occurred; if it had, silting would have followed. This indicates that spreading of silt over the bottom, raising the bottom by six inches (or less) has no measurable effect on wave scour of the bottom, even when the line of spread is at right angles to the prevailing current. The area of intense canal dredging in northeast Lake Grande Ecaille had no effect on the bottom elsewhere. Depths over the beds were found to be greater than those shown on current navigation charts based on data at least twenty years old. This was a result of general subsidence in the area. lt is believed that the build-up of silt on leases 9861 and 9864 was a result 'I •00 e>Slt.Hl:( '"O'o' S"O"t •u• FrG. 24. Number of forams on the Franks-Vujnovich leases as a function of distance from the shore. TABLE 13 Summary of foraminifera found in cores in the area of leases 9861 and 9864, Lake Grande Ecaille. Cores were taken on February 21, 1956 Depth to fresh· Mean no. Cor e Lenl: distanee from surface of e.ore water per inch no. 0-1" 2-3" 4--5" 6-i" 7-8'' 8--9" 9-10" 10-11" deposít of core 4 12 o 1-2" 6 5 23 7 2-3" 15 6 19 3 o 3--4" 4 7 32 50--100 3 4--5" 24 8 18 35 50 1 5--6" 26 9 150--200 300--400 28 o 5--6" 119 10 42 200--300 250--350 27 o 7--S" 104 11 150--250 200--300 250--350 20 8 8-9" 126 12 150--250 300-400 300-400 150-250 350-450 50--100 o 9-10" 186 13 50--100 50--100 o 3--4" 33 14 50--100 55 1 3--4" 35 15 24 32 100--200 50--100 5 o 8-9" 35 16 100--150 30 20 4--5" 50 17 150-'200 50-100 200--300 9 6 o 6--7" 83 18 200--300 200--300 200--300 600--SOO 15 o 7--S" 202 19 200--300 100--200 15 3 4--5" 79 20 100--150 500--600 2 3--4" 201 21 200--300 700--800 800--900 4 5--6" 426 22 50--100 150--250 1000--1500 o 4--5" 300 23 100--150 700--800 23 o 3--4" 206 24 250--350 300--400 400--500 --· ······· 10 8-9" 240 25 200-300 100--200 600--700 100--200 5 8-9" 201 26 100--200 300--400 150--250 900--1000 1200--1300 300-400 12-13" 491 27 150-250 100--200 200--300 Not 150 found-short core of this deepening, plus the diversion of current to the south of Franks' Island_ The huild-up of hottom was prohably a consequence of these two factors. Summary l. Those characteristics of Louisiana hays and hayous which have to do with under­standing of the problem of silting have heen discussed. The levees of the Mississippi have had far-reaching effects on the ecology of the Mississippi Delta area by preventing new deposits of sand, silts and clays. The marshes have contrihuted unusual amounts of muds high in organic content, which make up an increasing proportion of hottom deposits in hays and hayous. Suhsidence, compaction and rising sea level have produced conditions of high salinity and are responsihle primarily for deepening and widening of bays and disintegration of shorelines. As sediments are transported to the sea and he­cause little material is now deposited by the river, depths in hays are not in equilihrium with wind fetch and tidal current velocity. The amounts of turhid materials in waters of hays under natural conditions have heen reviewed, as have conditions having to do with settlement of particles of clay, silt and sand on the hottom. 2. Conditions around working dredges have heen studied. Measurements showed that silt is carried a maximum of ahout 1300 feet from working dredges under conditions for transport in shallow hays. Dilution has heen shown to he effective in reduction of tur­bidities around working dredges. The amount of spoil drifting away from dredges was TABLE 14 Foraminifera in the muds on the artificial reef area of the Franks-Vujnovich leases. Cores taken April 9, 1956 Order of dislance Distance Forams in topCore no. from shore from shore inch of core 150 1 250 15155 2 280 20151 3 318 75 58 4 375 100 156 5 387 47 57 6 398 15 64 7 412 150 161 8 420 100 56 9 438 75 152 10 448 75 55 11 490 200 63 12 490 56 157 13 492 12 160 14 526 38 54 15 547 350 6'2 16 555 75 153 17 562 150 53 18 585 18 67 19 590 75 158 20 61'2 150 61 21 612 75 52 22 639 250 154 23 657 75 60 24 677. 150 66 25 6'88 150 159 26 688 175 51 27 700 35 59 28 737 48 50 29 771 150 65 30 794 150 shown to be only a maximum of one percent of the total spoil dug from the bottom. Measurements of turbidities around working dredges have shodwn that in the close vicinity of the dredges these may be much higher than natural turbidities. At distances of a few hundred feet turbidities do not exceed those attained at times under natural conditions. 3. Experimental tests of the effect of suspended materials in water showed that con­centrations up to 700 parts per million had little effect on oysters, either on mortality rate or on feeding. 4. The possibility that spoils might significantly reduce oxygen was carefully con­sidered and was found to be unlikely' under conditions found on normal oyster beds. lt was also shown that the concept that dead oysters were significantly more effective in reduction of oxygen than were live oysters has no foundation in fact. 5. A concrete example of a problem involving claims of silting of oyster beds by canal dredging was thoroughly studied and the results of the study were presented. lt was shown that extensive dredging operations by the Humble Oil and Refining Company failed to produce general silting in Lake Grande Ecaille. It was also shown that these dredgings had nothing to do with accumulations of silt on oyster beds in southwest Lake Grande Ecaille as claimed. The methods and procedures involved ih resolution of problems of this type were presented. These involved analysis of many bottom corings at various points in Lake Grande Ecaille and on the oyster beds in question. lt was shown by these cores that the silt on the beds was derived from the disintegration of nearby shorelines and that the accumulation occurred over a long period of years. Literature Cited An asterisk ( *) indica tes the unpublished reports in depositories of the 28 libraries listed in the preface to this volume. Abbott, R. Tucker, 1954. American Seashells. D. Van Nostrand, New York, XIV. 541 p. Anderson, D. Q. 1940. Distribution of organic matter in marine sediments and its availability to further decomposition. J. Mar. Res. 2(3): 225-235. Austin, George R. 19'55. Current survey, West Barataria Bay, Louisiana. Texas A & M Research Foundation, Project 23. Cary, L. R. 1906. The conditions for oyster culture in the waters of the Parishes of Vermilion and Iberia, Louisiana. Gulf Biologic Station Bull. 4: 6-27. Collier, A. 1959. Sorne observations on the respiration of the American oyster Crassostrea virginica (Gmelin). Publ. lnst. Mar. Sci. Univ. Tex. 6: 92-'108. Ford, T. B. 1958. River basin studies, p. 126-131. In Seventh Biennial Report, Wildlife and Fisheries Commission, 1956-1957. Gaarder, T. and E. Alvsaker. 1941. Biologie und Chemie der Auster in den Norwegishen Pollen. Bergens Museums Arbok, 1941, Naturvitenskapelig rekke, nr 6, p. 236. Galtsoff, P. S. 1947. Respiration in oysters, p. 33-39. In Nat'l Shellf. Assoc. Convention Addresses for 1947. Galtsoff, P. S., and Dorothy V. Whipple. 1913. Oxygen consumption of normal and green oysters. Bu!!. U. S. Bur. Fish. 46: 489-508. Gowanloch, J. N. 1947. Oil and water must mix. Jefferson Parish Yearly Review, p. 12-23. Gunter, Gordon. 19S2. Historical changes in the Mississippi River and the adjacent marine environ­men t. Pub!. Inst. Mar. Sci. Univ. Tex. 2(2): 121-139. Gunter, Gordon. 1957a. What effect does siltation have on production? Gulf States Marine Fisheries Commission, Austin, Texas meeting, March 21-22, 1957. Gunter, Gordon. 1957b. How does siltation affect fish production? National Fisherman 38 (3): 18--19. Hewatt, W. G. 1949. Summary of hydrobiological conditions in Barataria Bay and related waters. July, 1945--September, 1947. Texas A & M Research Foundation, Project Nine Report. *Hewatt, W. G. 19'53. Ecological studies on salt marsh ponds in southern Louisiana. Texas A & M Research Foundation, Project Nine Report. Ingle, Robert M. 1952. Studies of the effect of dredging operations upon fish and shellfish. Tech. Series No. 5, Florida State Board Conservation, p. 1-26. Ingle, Robert M., and Charles E. Dawson. 1953. A survey of Apalachicola Bay. State of Florida, Board of Conservation, Tech. Series No. 10, p. 5-38. Ingle, Robert M., A. Russell Ceurvels and Richard Leinecker. 1955. Chemical and biological studies of the muds of Mobile Bay. Rep. Div. Seafoods, Alabama Dept. Conservation, p. 3-14. 1ensen, Fred. 1949. Unpublished data in possession of the author. Jung, Glenn. 1957. Flushing of Manilla Mayou, Louisiana. Gulf Consultants Report, Nov. 9, 1957, p. 1-10. Loosanoff, V. L. and F. D. Tommers. 1948. Effects of suspended silt and other substances on the rate of feeding of oysters. Science 107: 69-70. Lunz, G. Robert. 1936. The effects of the flooding of the Santee River in April, 1936, on oysters in the Cape Romain area of South Carolina. Mimeographed report to the U. S. Army Engineers, 24 p. Lunz, G. Robert. 1938. Oyster culture with reference to dredging operations. U. S. Engineers' Office, Charleston, South Carolina. Lunz, G. Robert. 1952. Handbook of oyster survey, lntracoastal Waterway, Cumberland Sound to St. John's River. Special Report, U. S. Army Engineers, Jacksonville, Florida. Lunz, G. Robert, and Nathaniel R. Bowman. 1955. Hilton Head oyster investigation, Beaufort County, South Carolina. Mimeographed, p. 1-15. Lynch, S. A. 1948a. Preliminary report on a current survey, Lake Grande Ecaille area, Louisiana. for Freeport Sulphur Company. Texas A & M Research Foundation, Project Nine Report. Lynch, S. A. 1948b. Depth study of Barataria Bay, Louisiana. Texas A & M Research Foundation, Project Nine, December, 1948. Lynch, S. A. 1948c. Water movements in Dupre Cut, p. 1-17. /n Texas A & M Research Foundation, Project Nine Report. Lynch, S. A. 1949. Current survey, intersection, Bayou Lafourche-Southwestern Louisiana Canal. Texas A &M Research Foundation, Project Nine, p. 1-27. Lynch, S. A. 1951. Bastian Bay Field hydrographic study. Texas A & M Research Foundation, Project Nine A Report. Mackin, J . G. 1954. A study of the capacity of disintegrating oysters to deplete oxygen in aquaria. Texas A & M Research Foundation, Project 23, Report No. 13. Mackin, J. G. 1956. Studies on the effect of suspensions of mud in sea water on oysters, p. 1-4. In Texas A &M Research Foundation Project 23, Tech. Report No. 19. *Mackin, J. G. 1960a. Canal dredging and silting in Louisiana. Texas A &M Research Foundation, Project 23 Report. Mimeographed. 94 p. Mackin, J. G. 1962. Oyster disease caused by Dermocystidium marinum and other microorganisms in Louisiana. Pub!. Inst. Mar. Sci. Univ. Tex. 7: 132-229. Mackin, J. G., and S. H. Hopkins. 1961. Results of Projects Nine and Twenty-three. A summary report. Vol. 1, Text. Texas A &M Research Foundation, Project 23 Report. Mackin, J. G., and S. H. Hopkins. 1962. Studies on oyster mortality in relation to natural environ­ments and to oil fields in Louisiana. Pub!. Inst. Mar. Sci. Univ. Tex. 7: 1-131. Ylackin, J . G., and A. K. Sparks. 1958. A study of the effects on oysters of crude oil loss from a wild well. Texas A & M Research Foundation, Project 23F Report. Marmer, H. A. 1935. The tides and currents in Timbalier and Terrebonne Bays. Typed report, un­published manuscript. Marmer, H. A. 1948. The currents in Barataria Bay. Texas A & M Research Foundation, Project Nine Report. Marmer, H. A. 1954. Tides and sea leve! in the Gulf of Mexico, p. 101-151. In Gulf of Mexico, its origin, waters, and marine life. Fishery Bulletin 89, U. S. Fish and Wildlife Service. McConnell, J . N. 1952a. Louisiana oyster's future. Louisiana Conservatitonist, January, 1952, 4(5): 5--9, 26. McConnell, J. N. 1952b. Report of Division of Oysters and Water Bottoms, Fourth Biennial Report, Department of Wildlife and Fisheries, State of Louisiana, for 1950-1951, p. 141-160. McConnell, J. N. 1953. Milestone resource meeting held. Louisiana Conservationist, November, 1953, 6(2}: 14-17. McConnell, J. N. 1%'4. Oil and oysters. Louisiana Conservationist, October, 1956, S(ll): 4--6. McConnell, J. N. 1957. Is physical improvement of adjacent land needed to improve fish production? Gulf States Marine Fisheries Commission, Austin, Texas meeting, March 21-22, 1957. McConnell, J. N. 1958. Report of the Oysters, Water Bottoms and Seafoods Division, Seventh Bien­nial Report, Wildlife and Fisheries Commission, 1956-1957, p. 65--69. Menzel, R. Winston. 1949. Effects of deep well gas on the mortality and growth of oysters. Texas A &M Research Foundation, Project Nine Report. Mi:iberg, E. G., R. H. Flemming, K. Heusner, and R. R. D. Revelle, 1937. The organic nitrogen con­tent of marine sediments off the West ·Coast of North America. Proc.-Verb. Assoc. Oceanogr. Phys. 2: 154. O'Neil, Ted. 1949. The muskrat in the Louisiana coastal marshes. Louisiana Department of Wildlife and Fisheries, New Orleans, Louisiana, XII. 152 p. Owen, H. Malcolm. 195.S. The Louisiana oyster industry, p. 1-387. In Special Report to the Division of Oyster Bottoms, Department of Wildlife and Fisheries of Louisiana. Rasmussen, W. C., and Lynch, S. A. 1949. The bottom sediments of Barataria Bay, 1934--1947. Texas A &M Research Foundation, Project Nine Report, p. 1-52. *Seiling, Fred W. 1951. Experiments on the effects of seismographic exploration on oysters in the Barataria Bay region. Texas A & M Research Foundation, Project Nine, Appendix B, p. 1-V. Sparks, A. K., J. L. Boswell, and J. G. Mackin. 1958. Studies of the comparative utilization of oxygen by living and dead oysters. Proc. Nat'I Shellf. Assoc. 48: 92-102. St. Aman!, Lyle S., E. J. Fairchild, A. V. Friedrichs, and B. E. Strawbridge. 1956. Biological Sec­tion, Oysters, Water Bottoms and Seafood Division, Sixth Biennial Report, State of Louisiana, Wildlife and Fisheries Commission, 1954-1955, p. 143-160. St. Amant, Lyle S., A. V. Friedrichs and Emory Hajdu. 1958. Report of the Biological Section, Oysters, Water Bottoms and Seafood Division, Seventh Biennial Report, Wildlife and Fisheries Commission, 1956-1957, p. 71-92. Strawbridge, Bruce H. 1956. Complaint: leases # 13224-13731, adjoining in Manilla Bayou and Snail Bay. Report to James N. McConnell and Lyle S. St. Amant, Division of Water Bottoms, State of Louisiana. Sverdrup, H. U., Martín W. Johnson, and Richard H. Fleming. 1942. The Oceans, Prentice-Hall, N. Y. 1087 p. Trask, P. D. 1939. Recent marine sediments. Amer. Assoc. Petrol. Geol. Tulsa, Oklahoma. 736 p. Viosca, Percy. (No date). Investigation of the claim of Gibson Collins for damages on five acres of his oyster leases in Manilla Bayou between St. Joseph's Bay and Colfee Bay (Snail Bay). Priva te report. Viosca, Percy, Jr. 1958. Report of the Seafood Section, Oysters, Water Bottoms and Seafood Divi­sion, Seventh Biennial Report, Wi!dlife and Fisheries Commission, 1956-1957, p. 96-106. Van Brand, Theodor. 1946. Anaerobiosis in invertebrates. Biodynamica Monographs, No. 4, p. 327, Biodynamica, Normandy 21, Missouri. Waksman, Selman A., and Margaret Hotchkiss. 1937. On the oxidation of organic matter in marine sediments by bacteria. J. Mar. Res. 1(2): 101-118. Wilson, W. B. 1950. The effects of dredging on oysters in Copano Bay, Texas, p. 1-50. In Annual Re­port of the Marine Laboratory of the Texas Game, Fish and Oyster Commission for 1948-1949. Publications of The Institute of Marine Science The University of Texas The Publications o/ the lnstitute o/ Marine Science is mailed in exchange with libraries and insti­tutions or provided by subscription at $4.15 per annual volume.t Write to the Librarían, lnstitute of Marine Science, Port Aransas, Texas. PUBLICATIONS OF THE INSTITUTE OF MARINE SCIENCE Volume I Number 1 Year 1945 Pages 190 tList Price (out of print) I 2 1950 194 (out of print) II 1 1951 212 $2.15 II 2 1952 215 $2.40 III l 1953 224 $2.15 III 2 1954 131 (out of print) IV l 1955 302 $2.65 IV 5 2• 1957 1958 341 492 $4.15 $4.40 6 1959 403 $4.15 7 8 (this volume). 1960 1961 319 $4.15 $4.15 * Beginning with Volume 5, each annual issue is numbered as a separate volume. t Prices include postage. Please add 2% sales tax. CUMULATIVE CONTENTS The contents of the volumes are listed below. For separate reprints write to the authors: Vol. 1, No. 1-May, 1945 Gunter, Gordon Studies on Marine Fishes of Texas, p. 1-199. Vol. 1, No. 2-November, 1950. Collier, Albert and Joel W. Hedgpeth An lntroduction to the Hydrography of Tidal Waters of Texas, p. 121-194. Gunter, Gordon Distribution and Abundance of Fishes on the Aransas National Wildlife Refuge, with Life History Notes, p. 89-101. Gunter, Gordon Seasonal Population Changes and Distributions as Related to Salinity, of Certain Invertebrates of the Texas Coast, including the Commercial Shrimp, p. 7-51. Hedgpeth, J. W. Notes on the Marine Invertebrate Fauna of Salt Flat Areas in the Aransas National Wildlife Refuge, Texas, p. 103-119. Whitten, H. L., H. F. Rosene, and J. W. Hedgpeth The Invertebrate Fauna of Texas Coast Jetties; a Preliminary Survey, p. 53-87. Vol. JI, No. 1-September, 1951 Burkenroad, Martín D. Sorne Principies of Marine Fishery Biology, p. 177-212. Hartman, Olga. The Littoral Marine Annelids of the Gulf of Mexico, p. 7-124. Ladd, Harry S. Brackish-Water and Marine Assemblages of the Texas Coast, with Special Reference to Mollusks, p. 125-163. Post, Rita J. Foraminifera of the South Texas Coast, p. 165-176. Vol. JI, No. 2-December, 1952 Carlgren, Oskar and Joel W. Hedgpeth Actiniaria, Zoantharia and Ceriantharia from Shallow Water in the Northwestem Gulf of Mexico, p. 141-172. Ginsburg, Isaac Fishes of the Family Carangidae of the Northern Gulf of Mexico and Three Related Species, p. 43-117. Gunter, Gordon Historical Changes in the Mississippi River and the Adjacent Marine Environment, p. 119-139. Olsen, S. Leland Sorne Nematodes Parasitic in Marine Fishes, p. 173-215. Pearse, A. S. Parasitic Crustacea from the Texas Coast, p. 5-42. Vol. lll, No. J-October, 1953 Causey, David Parasitic Copepoda of Texas Coastal Fishes, p. 5-16. Gunter, Gordon The Relationship of the Bonnet Carré Spillway to Oyster Beds in Mississippi Sound and the "Louisiana Marsh", with a Report on the 1950 Opening, p. 17-71. Hedgpeth, Joel W. An Introduction to Zoogeography of the Northwestern Gulfo f Mexico with Reference to the Invertebrate Fauna, p. 107-224. Heegaard, Poul E. Observations on Spawning and Larval History of the Shrimp, Penaeus seti/erus (L.), p. 73-105. Vol. III, No. 2-Novernber, 1954 Hildebrand, Henry H. A Study of the Fauna of the Brown Shrirnp (Penaeus aztecus !ves) Grounds in the Western Gulf of Mexico, p. 1-366. Vol. IV, No. J-September, 1955 Causey, David The Externa) Morphology of Blias prionoti Krllyer, a Copepod Parasite of the Sea Robins (Prinonotus), p. 5-11. Dawson, C. E. A Contribution to the Hydrography of Apalachicola Bay, Florida, p. 13-35. A Study of the Oyster Biology and Hydrography at Crystal River, Florida, p. 279-302. Geyer, Richard A. Effect of the Gulf of Mexico and the Mississippi River on Hydrography of Redfish Bay and Blind Bay, p. 155-168. Gunter, Gordon and Richard A. Geyer Studies on Fouling Organisrns of the Northwest Gulf of Mexico, p. 37-67. Hildebrand, Henry H. A Study of the Fauna of the Pink Shrimp (Penaeus duorarum Burkenroad) Grounds in the Gulf of Campeche, p. 169-232. Koratha, Kunnenkeri, J. Studies on the Monogenetic Trernatodes of the Texas Coast. I. Results of a survey of marine fishes at Port Aransas, with a review of Monogenea reported from the Gulf of Mexico and notes on euryhalinity, host-specificity, and relationship of the Rernora and the Cobia, p. 233-249. Studies on the Monogenetic Trematodes of the Texas Coast. II. Descriptions of species from ma­rine fishes of Port Aransas, p. 251-278. Menzel, R. Winston Sorne Phases of the Biology of Ostrea equestris Say and a cornparison with Crassostrea virginica ( Grnelin), p. 69-153. Vol. IV, No. 2-July, 1957 Breuer, Joseph P. Ecological Survey of Baffin and Alazan Bays, Texas, p. 134-155. Bullock, W. L. The Acanthocephalan Parasites of the Fishes of the Texas Coast, p. 278-283. Fingerrnan, Milton Body Fluid of the Üyster Crassostrea virginica, p. 284-292. Hurnrn, Harold The Surnrner Marine Flora of Mississippi Sound, p. 228-264. Loesch, Harold Studies on the Ecology of Two Species of Donax on Mustang lsland, Texas, p. 201-227. Lund, E. J. Effect of Bleedwater, "Soluble Fraction" and Crude Oil on the Oyster, p. 3'28-341. A Quantitative Study of Clearance oí a Turbid Mediurn and Feeding by the Oyster, p. 296-312. Self-silting by the Oyster and lts Significance for Sedirnentation Geology, p. 320-327. Self-silting, Survival of the Oyster as a Closed Systern and Reducing Tendencies of the En­vironrnent of the Oyster, p. 313-319. Lund, E. J., and Ernest Powell Note on the Reflex lnhibition of Water Propulsion by the Oyster, p. 293-295. Moon, F. W., Jr., Charles L. Bretschneider and Donald Hood A Method for Measuring Eddy Diffusion in Coastal Ernbayrnents, p. 14-21. Odurn, Howard T. Biogeochernical Deposition of Strontiurn, p. 38-114. Strontiurn in Natural Waters, p. 22-37. Odum, Howard T., and Charles M. Hoskin Metabolism of a Laboratory Stream Microcosm, p. '115--133. Robinson, Maryanne The Effect of Suspended Materials on the Reproductive Rate of Daphnía Magna, p. 265--27í. Shepard, Francis P., and Gene A. Rusnak Texas Bay Sediments, p. 5-13. Simmons, Ernest G. Ecological Survey of the Upper Laguna Madre of Texas, p. 156-200. Vol. 5-December, 1958 (Mailed in May, 1959) Conover, John T. Seasonal growth of Benthic Marine Plants as Related to Environmental Factors in an Estuary, p. 97-147. Darnell, Rezneat M. Food Habits of Fishes and Larger Invertebrates of Lake Pontchartrain, Loúisiana, an Estuarine Community, p. 353-416. Gunter, Gordon Population Studies of the Shallow Water Fishes of an Outer Beach in South Texas, p. 186-193. Hellier, Thomas R., Jr. The Drop-Net Quadrat, a New Population Sampling Device, p. 165--168. Hoese, Hinton D. A Partially Annotated Checklist of the Marine Fishes of Texas, p. 312-352. Hopkins, Sewell H. Trematode Parasites of Donax variabilis at Mustang Island, Texas, p. 301-311. Kornicker, Louis S. Ecology and Taxonomy of Recent Marine Ostracodes in the Bimini Area, Great Bahama Bank, p. 194-300. Kornicker, Louis S., Carl H. Oppenheimer, and John T. Conover. Artificially Formed Mudballs, p. 148-150. Moore, Donald R. Notes on Blanquilla Reef, the }lost Northerly Coral Forrnation in the Western Gulf of }1exico, p. 151-155. Morita, Richard Y. An Incidence of Pink Oysters in Galveston Bay, Texas, p. 163-164. Odum, Howard T., William McConnell, and Walter Abbott The Chlorophyll "A" of Communities, p. 65--96. Odum, Howard T., and Charles M. Hoskin Comparative Studies on the Metabolism of Marine Waters, p. 16-46. Oppenheimer, Carl H. A Bacterium Causing Tail Rot in the Norwegian Codfish, p. 160-162. Evidence for Fossil Bacteria in Phosphate Rocks, p. 156-159. Oppenheimer, Car! H., and Louis S. Kornicker Effect of the Microbial Production of Hydrogen Sulfide and Carbon Dioxide on the pH of Recent Sediments, p. 5--15. Park, Kilho, Donald W. Hood, and Howard T. Odum Diurna! pH Variation in Texas Bays, and its Application to Primary Production Estimation, p. 47-64. Springer, Víctor G. Systematics and Zoogeography of the Clinid Fishes of the Subtribe Labrisomini Hubbs, p. 417-492. Springer, Víctor G., and Jacques Pirson Fluctuations in the Relative Abundance of Sport Fishes as Indicated by the Catch at Port Aransas, Texas 1952-1956, p. 169-185. Vol. 6-1959 (Mailed in June, 1960) Bruce, H. E., and Donald W. Hood Diurna! Inorganic Phosphate Variations in Texas Bays, p. 133-145. Chambers, Gilbert V., and Albert K. Sparks An Ecological Survey of the Houston Ship Channel and Adjacent Bays, p. 213-250. Collier, Albert Sorne Observations on the Respiration of the American Oyster Crassostrea virginica (Gmelin 1, p. 92...:108. Curl, Herbert, Jr. The Hydrography of the Inshore, Northwestern Gulf of Mexico, p. 193-205. The Phytoplankton of Apalachee Bay and the Northeastern Gulf of Mexico, p. 277-3'20. Hillis, Llewellya W. A Revision of the Genus Halimeda