COMPARISON OF ECOSYSTEM STRUCTURE AND FUNCTION OF CREATED AND NATURAL SEAGRASS HABITATS IN LAGUNA MADRE, TEXAS Paul A. Montagna, Principal Investigator Cooperative Agreement No. X-00658801 -0 Technical Report Number TR/92-003 ANNUAL REPORT COMPARISON OF ECOSYSTEM STRUCTURE AND FUNCTION OF CREATED AND NATURAL SEAGRASS HABITATS IN LAGUNA MADRE, TEXAS by •, Paul A Montagna, Principal Investigator from University of Texas at Austin Marine Science Institute P.O. Box 1267 Port Aransas, Texas 78373 to Dr. James H. Ratterree, Project Orne.ex ~f=iter Management Division (6W-0Ui) 1 U.S. Environmental Protection Agency, Region 6 1445 Ross Avenue Dallas, Texas 75202-2733 Cooperative Agreement No. X-00658801-0 The University of Texas Marine Science Institute Technical Report Number TR/92-003 October 1992 COMPARISON OF ECOSYSTEM STRUCTURE AND FUNCTION OF CREATED AND NATURAL SEAGRASS HABITATS IN LAGUNA MADRE, TEXAS TABLE OF CONTENTS LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii ABSTRACT........ .................... ............... .... .... I INTRODUCTION 2 METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Study Site Descriptions . . . . . . . . . :-. . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Hydrographic Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Geological Measurements .............. .........·. . . . . . . . . . . . 7 Chemical Flux Measurements ................... , .' . . . . . . . . . . . . 8 Biological Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Statistical Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 DISCUSSION .. ....... .. ..... ......... ........ .. ... c • • • • ~t 1 ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i 1 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 LIST OF FIGURES Figure 1. Upper Laguna Madre. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Figure 2. Northern part of Upper Laguna Madre. . . . . . . . . . . . . . . . . . . . . . . . 4 LIST OF TABLES Table 1. Sampling locations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Table 2. Hydrographic measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Table 3. Sediment grain size in the Guadalupe Estuary . . . . . . . . . . . . . . . . . . . 15 Table 4. Eh profiles in sediment cores. 16 Table 5. Nutrient measurements in sample incubations. . . . . . . . . . . . . . . . . . . . 17 Table 6. Oxygen measurements in sample incubations. . . . . . . . . . . . . . . . . . . . 21 COMPARISON OF ECOSYSTEM STRUCTURE AND FUNCTION OF CREATED AND NATURAL SEAGRASS HABITATS IN LAGUNA MADRE, TEXAS ABSTRACT The goal of this project is to determine how long it takes for created seagrass habitats to function like natural habitats. Two approaches are taken. The first is a synoptic study of mitigated sites of different ages, the second is a multi-year monitoring of a recent mitigation site. Ecosystem structure and function is assessed by measuring select variables. Community metabolism and nutrient regeneration are key variables, which indicate the functioning of an ecosystem. Benthic community structure is a key variable that indicates the habitat utilization of an ecosystem. The mitigation sites are compared to three natural reference sites that have been studied since 1989. INTRODUCTION Biological interactions between plants and animals have a profound effect on the success of any habitat creation project. There is a succession of events leading to the climax, mature seagrass community. This process includes colonization of the transplanted area by microbes, epiphytes, and benthic invertebrates. The microbial community is important in maintaining the balance of available nutrients, which are necessary for plant growth. The objectives of this study are to 1) compare benthic metabolism, 2) nutrient regeneration, and 3) habitat utilization of created seagrass habitats of different ages with natural habitats. The goal of collecting this data is to determine how, and when created habitats become functioning ecosystems like natural systems. The Gulf of Mexico Program was established to develop and implement a comprehensive strategy for managing and protecting the resources of the Gulf. Habitat degradation was identified as an important issue because of historic and current losses of many important habitats along the Gulf of Mexico. The Habitat Degradation Subcommittee has identified the natural and man-induced loss of seagrass communities as particularly insidious. Seagrass habitats are important habitats for many marine and estuarine species including many species of commercial and/or recreational importance. This study will result in the definition of important ecological parameters. This information is necessary to assure success of seagrass plantings, define measures of success, and delineate how long it takes a planted system to provide the ecological functions that are provided by naturally occurring seagrass systems. I n I 1 0 I _,,_ 2 " 0' r s Figure 1. Upper Laguna Madre. Natural reference are in Baffin Bay (6), and Ht:J '....'~,g~na Madre (189) . Mitigation sites are between the shorelines of the cities of Flour Bluff and Padre Isles. Figure 2. Northern part of Upper Laguna Madre. Location of mitigation sites are showri _ Dasheded lines represent dredged channels. METHODS Study Area Ten study sites were chosen in the Upper Laguna Madre and Baffin Bay (Table 1 ). Two of the sites have been visited since 1989 as part of a long-term research project to determine the importance of seagrass beds in maintaining a productive finfishery (Figure 1). These sites are 189 in the southern upper Laguna Madre and 6 in Baffin Bay (Table 1). Eight of the sites were located in a small area in the northern Upper Laguna Madre between the Flour Bluff and Padre Isles shorelines (Figure 2). At three sites, there are two paired station locations. One station is located in the grass bed, and one station is adjacent in a bare patch. These paired stations are located in sites 189, TS and GI. They are named for the grass (-G) and sand (-S) respectively as: 189G, 189S, TSG, TSS, GIG, and GIS. Study Site Descriptions Gulf Isles Limited (GI_), project #9009(08) is located east of lntracoastal Watervvay Marker 49. The project scraped down a spoil island and created an area of submerged habitat approximately 320 m x 168 m with six circulation channels in April, 1991. Seagrass planting was not required. Natural colonization by Ruppia maritima, Halodule wrightii and Halophila engelmannii appears to have been successful. Two sites were sampled in the southern end of the excavation at a depth of 0.4 m. One site was in a mixed bed of H. engelmannii and R. maritima (GIG) and the other was an adjacent bare sand patch (GIS). The sediment was firm in both areas composed of approximately 90% sand, 5% rubble, 2% silt and 3% clay. Padre Isles Natural Site #1 (Pl1G) was located in an open area east of the Gull­Isles site and west of the Padre Isles development. this site is protected from high wave action due to the surrounding land resulting in a low energy area. Most of this area is covered with a mixture of H. wrightii and R. maritima with few bare patches. Core samples were taken from a bed of H. wrightii at a depth of 0.5 m. The sediment was very soft and smelled of H2S when disturbed. The upper 3 cm of sediment was composed of 10% rubble, 55% sand, 10% silt, and 25% clay while from 3 to 10 cm depth sand increased to 90%. Padre Isles Natural Site #2 (Pl2G) was located in the center of a seagrass flat east of the spoil islands adjacent to lntracoastal Waterway Marker 63 and west of Padre Island. The dominant seagrass at this site is H. wrightii. Samples were taken at a depth of 0. 75 min a bed of H. wrightii. The sediment was firm compared to Pl1 with more rubble 14% and sand 74% and less silt 25% and clay 10%. The deeper sediment was sandy 89%; i.e. Pl1 . Transco scrape-down (TS_) project #18853 is located in state land tract 64 on a spoil island east of lntracoastal Waterway Marker 55. Submerged habitat was developed by scraping down an existing spoil island, cutting three circulation channels and planting H. wrightii. Samples were taken from H. wrightii (TSG) and bare sand (TSS) in a water depth of 0.4 m. The sediment was very firm composed primarily of sand in the grass (88%) and the bare_patches (95%). Transco pipeline (TPG) project #18853 was an attempt to establish seagra~s, /-1. wrightii, on the bare shoulders of a pipeline extending from Padre Island in state land tract # 174, and 64 under the lntracoastal Waterway near Marker 59, and through state tracts 48, 47, 25 and 134 to the mainland. The site sampled was located east of the spoil islands adjacent to marker 59 near the area where the pipeline crossed the state tract boundary between state tracts 64 and 174. The water depth was 0.6 m and the dominant grass along this section of the pipeline was R. maritima. The sediment was firm composed 95% of sand. Central Power and Light Company (CPG) project #10444 is located on the west Laguna Madre shoreline adjacent to the CP&L mariculture ponds. The project resulted in the removal of dredged material covering submerged seagrasses and was described as being successful. The project site is in a small cove formed by a point of land to the north with the opening facing the southeast Southerly winds deposit dead seagrass along the shoreline and on the bottom. Ruppia maritima was the dominant seagrass and was sparse. The water depth was 0.55 m and the sediment was very soft The upper 3 cm of sediment sampled was 9% rubble, 70% sand, 12% silt, and 9% clay and the 3· IQ cm sediment layer was 10% rubble, 79% sand 1% silt and 10% clay. Skyline Equipment, Inc. (SKG) project #12004 (03) is located on the west Lo.gun<:; Madre shoreline just north and adjacent to the Central Power and Light project. The project created 0.14 ha (0.34 acre) of submergent habitat from uplands. Th0 site is located on a point and is exposed to high energy southeast and northerly winds resulting in minimal dead seagrass deposition. The bottom was covered with approximately 25% Ruppia maritima, 25% Halodule wrightii and 50% bare sand. Core samples were taken in H. wrightii at a depth of 0.35 m. The sediment was composed mainly of firm sand (92%). Marker 189 (189 _) is a control site in an open grass flat to the west of lntracoastal Waterway Marker 189. This site is vegetated with Halodule wrightii with scattered bare patches and very little drift algae and dead seagrass debris. The water depth is 0.8 m. Samples were taken from the grass (189G) and an adjacent bare patch (189S). The sediment in the bare patch sampled was firm composed of 21% rubble, 61% sand, 3% silt and 15% clay. The grass sediment was similar with 21% rubble, 50% sand, 4% silt and 19% clay. The amount of clay increased with depth (35%) in the sandy bare patches and the seagrass. Genesis Petroleum (GES) project #15844 is located between two dredge spoil islands east of lntracoastal Waterway Markers 67. Approximately 0.4 ha (0.9 acre) of submerged wetland was created from the emergent spoil island. The site is in a small cove which faces southeast into the prevailing wind. Dead seagrass and detritus collect along the shoreline and on the bottom. Although H. wrightii was planted following the scrape-down, no living seagrass was found at the site. The water depth was 0.9 m. The surface sediment was 63% sand and 31% clay. Below 3 cm the sediment was 94% sand. Marker 6 (BB6) is a control site located approximately 180° off of Marker 6 at the mouth of Baffin Bay. This site is in the open bay in 2.2 m water depth without seagrass. The sediment is soft mud predominantly silt (15%) and clay (81%). Hydrographic Measurements Salinity, conductivity, temperature, pH, dissolved oxygen, and redox potential were measured at the surface and bottom at each station during each sampling trip. Measurements were made by lowering a probe made by Hydrolab Instruments. Salinities levels are automatically corrected to 25 ° C. The manufacturer states that the accuracy of salinity measurements are 0.1 ppt. When the Hydrolab instrument was not working, water samples were collected from just beneath the surface and from the bottom in jars, and refractometer readings were made at the surface. Geological Measurements Sediment grain size analysis was also performed. Sediment core samples were taken by diver and sectioned at depth intervals 0-3 cm and 3-10 cm. Analysis followed standard geologic procedures (Folk, 1964; E. W. Behrens, personal communication). Percent contribution by weight was measured for four components: rubble (e.g. shell hash), sand, silt, and clay. A 20 cm3 sediment sample was mixed with 50 ml of hydrogen peroxide and 75 ml of deionized water to digest organic material in the sample. The sample was wet sieved through a 62 µm mesh stainless steel screen using a vacuum pump and a Millipore Hydrosol SST filter holder to separate rubble and sand from silt and clay. After drying, the rubble and sand were separated on a 125 µm screen. The silt and clay fractions were measured using pipette analysis. Chemical Flux Measurements Biogeochemical fluxes were measured in the same 6. 7 cm diameter core tubes that were used to sample macrofauna. Samples were taken by hand to a depth of 10 cm by divers. Three replicates were taken within a 2 m radius. The water level was brought to the top with added station water, after about 1 Ominutes the initial sample was taken. The cores were closed with rubber stoppers that had an oxygen probe and a relief valve so that a tight seal could be obtained. Cores were incubated in the dark for two hours. Ice chest coolers were used as incubation chambers. The coolers had station seawater circulated through them, via a pump, to maintain the temperature as near to ambient conditions as possible. Three replicate cores were used for determine sediment metabolism and nutrient regeneration. One station water sample was incubated as a control for oxygen metabolism, and two control samples were incubated for nutrient regeneration. Oxygen concentration changes were measured every 15 min using pulsed oxygen electrodes (Endeco, Inc., Marion, MA). These electrodes are of a new design in which the measurement of oxygen concentration is flow-insensitive (Langdon, 1984). The electrodes are connected to a Pulsed D.O. SensorTW that controls the timing of the electrical pulses sent to each probe. Data is interpreted by the Pulsed D.O. Sensor and logged automatically on a portable computer. Water samples were taken after the final two hours to measure changes in other chemical constituents. Inorganic nitrogen concentrations of ammonia, nitrate, and nitrite were measured from the water subsamples using highly precise autoanalyzer techniques (Whitledge et al., 1986). Oxygen changes were estimated using linear regression analysis. Nuthent changes were estimated as the difference from initial and ending values. The flux is calculated a product of the slope with respect to time, and was adjusted for the area of sediment covered by the core and the volume of water contained in the core. Biological Measurements Sediment was collected from the same 6. 7 cm diameter core tube, that wa'2 usecl to measure chemical flux. The macrofauna were sectioned at depth intervals of 0-3 cm and 3-10 cm (Montagna and Kalke, 1992). Samples were preserved with 5% buffered formalin, sieved on 0.5 mm mesh screens, sorted, identified, and counted. Each macrofauna sample was also used to measure biomass. Individuals were combined into higher taxa categories, i.e. , Crustacea, Mollusca, Polychaeta, Ophiuroidea, and all other taxa were placed together in one remaining sample. Samples were dried for 24 hat 55 °C, and weighed. Before drying, mollusks were placed in 1 N HCI for 1 min to 8 h to dissolve the carbonate shells, and washed with fresh water. Statistical Analyses Statistical analyses to reveal differences among cruises, stations and sediment depths were performed using general linear model procedures (SAS, 1985). Two-way analysis of variance (ANOVA) models were used where sampling dates and stations were the two main effects. Tukey multiple comparison procedures were used to find a posteriori differences among sample means (Kirk, 1982). Multivariate ANOVA was used to test for treatment effects on species data. Factor analysis with rotated and unrotated factors was used to determine if communities were similar on different sampling dates. Linear correlation coefficients were calculated to determine if salinity was correlated to macrofauna abundance, biomass or diversity. Diversity is calculated using Hill's diversity number one (N1) (Hill, 1973). It is a measure of the effective number of species in a sample, and indicates the number of abundant species. It is calculated as the exponentiated form of the Shannon diversity index: N1 = eH' (1) As diversity decreases N 1 will tend toward 1. The Shannon index is the average uncertainty per species in an infinite community made up of species with known proportional abundances (Shannon and Weaver, 1949). The Shannon index is calculated by: (2) H'--t[(:;H:;)] Where ni is the number of individuals belonging to the ith of S species in the sample and n is the total number of individuals in the sample. Richness is an index of the number of species present. The obvious richness index is simply the total number of all species found in a sample regardless of their abundances. Hill (1973) named this index NO. Another well known index of species richness is the Margalef (1958) index (R1). R1 is based on the relationship between the number of species (S) and the total number of individuals (n) observed: Rt-S-1 (3) ln(n) Although common, this relationship presupposes that there is a functional relationship between Sand n. This assumption may not be justified in all cases. Evenness is an index that expresses that all species in a sample are equally abundant. Evenness is a component of diversity. Two evenness indices, E1 and E5, have been calculated. E1 is probably the most common, it is the familiar J' of Pielou (1975). It expresses H' relative to the maximum value of H': Et-___!f_ -ln(Nt) (4) ln(S) ln(NO) E1 is sensitive to species richness. E5 is an index that is not sensitive to species richness. E5 is a modified Hill's ratio (Alatalo, 1981): E5-(1/1..) -1 Nt-1 (5) s nf..n.-1) where,1.. -L '. i-1 n(n-1) >. is the Simpson (1949) diversity index. E5 approaches zero as a single species becomes more and more dominant. RESULTS Salinity and temperature were similar at all stations (Table 2). Differences in oxygen concentration were due to site differences and sampling at different times of the day. Baffin Bay was the only site with high turbidity. There was considerable difference in sediment composition at all sites (Table 3). Baffin Bay was the only site dominated by mud with a high silt and clay content. 'Niih:r·1 sites, bare patches had higher sand content than vegetated sediments. Eh decreased with sediment depth at all stations (Table 4). There were dramatic differences among sites in sediment Eh profiles. Vegetated sediments were always much more negative than pare-patch sediments within sites. There was a gradient of electronegativity from recent mitigation sites to older mitigation sties to natural sites. This indicates that there is a lack of organic matter in recent sediments. Raw data for calculating nutrient regeneration is given in Table 5. Flux calculations will be made soon, after final quality control checks on the data. Raw data for calculating oxygen metabolism is given in Table 6. Flux calculations will be made soon, after final quality control checks on the data. A total of 39 ( =13 stations x 3 replicates) benthic samples have been sorted and organisms identified. This data has not yet been organized into a database. It will be reported on in the final report. DISCUSSION This is a preliminary data report. The final report is due March 31, 1993. However, one important discovery has already been made. The Eh profiles show dramatic differences among natural and mitigation sites, and also suggest trends with mitigation site aging. Eh is a measure of the total electronegativity of the sediment. Reduced ions, e.g., NH4 and H2S are major contributors to Eh. These ions are evolved in the anaerobic respiration of organic matter. So, Eh can be thought of as the total number of available electron donors. Low Eh values were typical of sediments in recent mitigation sites. This indicates there is very low organic content in these sediments. This ecosystem is not functioning like a natural ecosystem. ACKNOWLEDGEMENTS I would like to thank Mr. Rick Kalke, the University of Texas Marine Science Institute, for his invaluable help on all aspects of this project. REFERENCES Alatalo, RV. 1981. Problems in the measurement of evenness in ecology. Oikos, 37: 199­ 204. Folk, R. L. 1964. Petrology of sedimentary rocks. Hemphill's Press. Austin, TX. 155 pp. Hill, M. 0. 1973. Diversity and evenness: a unifying notation and its consequences. Ecology. 54:427-432. Kirk R E. 1982. Experimental Design. 2nd Ed. Brooks/Cole Publ. Co., Monterey, California, 911 p. Langdon, C., 1984. Dissolved oxygen monitoring system using a pulsed electrode: design, performance, and evaluation. Deep Sea Research, 31 :1357-1367. Margalef, R. 1958. Information theory in ecology. General Systematics, 3:36-71. Montagna, P.A. and RD. Kalke. 1992. The effect of freshwater inflow on meiofaunal and macrofaunal populations in the Guadalupe and Nueces Estuaries, Texas. Estuaries, 15:307-326. Nixon, S. A., C.A. Oviatt, J. Frithsen, B. Sullivan. 1986. Nutrients and the productivity of estuarine and coastal marine ecosystems. Journal of the Limnological Society of South Africa, 12:43-71 Pielou, E.C. 1975. Ecological Diversity. Wiley, New York. SAS Institute, Incorporated. 1985. SAS/STAT Guide for Personal Computers, Version 6 Edition. Cary, NC:SAS Institute Inc., 378 pp. Shannon, C. E. and W. Weaver. 1949. The Mathematical Theory of Communication. University of Illinois Press. Urbana, IL. Simpson, E.H. 1949. Measurement of diversity. Nature, 163:688. Whitledge, T.E., Veidt, D.M., Malloy, S.C., Patton, C.J. Wirich, C.D. 1986. Autornated nutrient analysis in seawater. Brookhaven National Laboratory Report 38990. Upton, New York, 231 pp. Table 1. Sampling locations. Station Location Habitat Date Project GIG N Upper Laguna Grass APR91 Gulf Isles Limited 9009(08) GIS N Upper Laguna Sand APR91 Gulf Isles Limited 9009(08) Pl1G N Upper Laguna Grass Natural Padre Isles Site 1 P12G N Upper Laguna Grass Natural Padre Isles Site 2 TSG N Upper Laguna Grass APR90 Transco Scrape-down 18853 TSS N Upper Laguna Sand APR90 Transco Scrape-down 18853 TPG N Upper Laguna Grass APR90 Transco Pipeline 18853 CPG N Upper Laguna Grass AUG75 Central Power and Light 100444 SKG N Upper Laguna Grass ? Skyline Equipment, Inc. 12004(03) GES N Upper Laguna Sand OCT83 Genesis Petroleum 15844 189G S Upper Laguna Grass Natural West of ICW Marker 189 189S S Upper Laguna Sand Natural West of ICW Marker 189 BB6 Baffin Bay Mud Natural North of BB Marker 6 site Table 2. Hydrographic measurements. Abbreviations: STA= Station, Z =Depth, SAL(R)= Salinity by refractometer, SAL(M)= Salinty by meter, COND= Conductivity, TEMP= Temperature, DO= dissolved oxygen, and ORP = oxidation red ox potential. Missing values show with a period. Date STA z SAL(R) SAL(M) COND TEMP pH DO ORP NTU (m) (ppt) (ppt) (uS/cm) (·c) (mg. r') (mV) 22APR92 GIG 0.00 24 23.4 37.10 22.46 9.19 6.31 0.094 4.4 22APR92 GIG 0.10 24 23.5 37.20 22.51 9.09 6.25 0.097 4.4 22APR92 Pl1 0.00 24 23.2 36.80 26.95 9.81 12.63 -0.055 22APR92 Pl1 0.20 24 23.4 37.00 26.93 9.93 12.36 -0.026 23APR92 886 0.00 24 23.6 37.40 24.33 8.56 7.68 0.137 20.0 23APR92 886 2.20 24 27.0 42.10 23.90 8.85 5.20 0.130 20.0 23APR92 189 0.00 26 25.5 40.00 26.13 9.27 9.40 o.·1 00 5.5 23APR92 189 0.80 26 25.5 40.00 26.07 9.52 8.92 0.098 5.5 24APR92 TSS 0.00 24 23.8 37.70 25.15 8.60 4.21 0.149 6.6 24APR92 TSS 0.40 24 23.8 37.70 25.15 8.60 4.21 0.149 6.6 24APR92 TSG 0.00 24 23.9 37.70 25.43 8.64 5.72 0.132 6.6 24APR92 TPG 0.00 26 24.4 38.40 26.27 8.64 6.14 0.126 6.6 24APR92 TPG 0.60 26 24.5 38.50 26.29 8.77 6.07 0.1 26 6.3 27APR92 SKG 0.00 25 24.2 38.20 22.14 8.37 7.30 0.-139 5.2 27APR92 SKG 0.35 25 24.2 38.20 22.14 8.37 7.30 o. ·139 5.2 27APR92 CPL 0.00 25 25.0 39.30 24.17 9.12 8.49 0.089 6.0 27APR92 CPL 0.55 25 25.0 39.30 24.17 9.12 8.49 0.08J 6.0 28APR92 GES 0.00 25 24.8 38.30 21.78 9.19 5.13 0. 108 -19.0 28APR92 GES 0.90 25 24-7 38.30 21.76 8-93 4.96 0.289 19.0 28APR92 Pl2 0.00 26 25.0 39.20 23.67 9.41 8.40 0.098 28APR92 Pl2 0.75 26 25.0 39.40 23.65 9.44 8.38 0.100 08JUL92 TS 0.00 21 20.5 33.00 32.91 8.80 8.1 0 0. i7i Table 3. Sediment grain size in the Guadalupe Estuary. Mean of n replicates. Date Station Depth Rubble Sand Silt Clay (cm) (%) (%) (%) (%) Table 4. Eh profiles in sediment cores. Values are the oxidation redox potential in mV at the sediment depth horizon. Missing values show with a period. 23APR92 886 3 1.4 3.3 14.7 80.6 23APR92 886 10 3.9 8.4 19.8 67.9 23APR92 189G 3 20.7 55.9 3.8 19.6 23APR92 189G 10 10.3 47.7 7.4 34.5 23APR92 189S 3 20.9 60.7 3.1 15.2 23APR92 189S 10 10.9 50.3 5.2 33.6 23APR92 GIG 3 4.3 83.1 4.2 8.5 23APR92 GIG 10 2.5 89.3 2.6 5.5 23APR92 GIS 3 5.0 90.7 2.1 2.1 23APR92 GIS 10 4.5 90.3 1.8 3.3 23APR92 Pl1 3 9.7 54.5 10.1 25.7 23APR92 Pl1 10 1.0 91 .8 1.4 5.8 24APR92 CPG 3 8.8 70.2 12.3 8.7 24APR92 CPG 10 10.4 78.8 i.O 9.8 24APR92 GE2 3 0.8 68.7 4.5 26.0 24APR92 GE2 10 5.4 90.6 0.0 4.0 24APR92 GES 3 0.5 62.7 5.8 31.0 24APR92 GES 10 1.7 94.2 0.1 4.0 24APR92 P1G 3 14.0 73.6 2.1 10.3 24APR92 P1G 10 3.9 89.4 1 ·',•I 5.6 24APR92 SKG 3 4.0 91.2 0.4 4.5 24APR92 SKG 10 2.2 92.2 3.4 2.2 24APR92 TPG 3 2.2 94.5 0.4 2.9 24APR92 TPG 10 2.7 94.8 0.6 1.9 24APR92 TSG 3 4.6 87.6 2.0 5.8 24APR92 TSG 10 14.6 83.2 0.9 1.3 24APR92 TSS 3 2.4 94.5 1.0 2.0 24APR92 TSS 10 3.7 93.9 1.3 1.1 Sediment Depth (cm) Date Station 0 1 2 3 4 5 6 7 8 9 10 22APR92 GIG 66 30 18 -4 -14 -10 -4 -9 -7 -1 4- -3 22APR92 GIS 25 -245 -7 -10 -9 -10 -12 -15 4 6 22APR92 Pl1G 6 -285 -320 . -310 -320 -20 -147 -173 -240 23APR92 886 94 39 21 -18 -400 -48~ -451 -431 -432 -422 23APR92 189S 6 -355 -327 -325 -330 -300 -240 -326 -333 -345 23APR92 189G-150 -326 -364 -363 -357 -355 -362 -360 -357 -348 -352 24APR92 TSS 22 20 0 -1 0 0 -4 -6 -2 -4 -5 24APR92 TSG 23 20 13 3 -1 -18 -50 -71 -150 -150 -140 24APR92 TPG 22 13 8 -1 -25 -40 -67 -110 -120 -200 -i 10 27APR92 SKG 40 32 32 29 28 22 17 7 -91 -290 ~306 27APR92 CPG 25 -220 -260 -310 -326 -310 -353 -334 -339 -330 -376 28APR92 GES 4 -200 -313 -388 -330 -344 -285 -230 -275 -305 -319 28APR92 Pl2G 48 -9 -275 -350 -343 -347 -333 -336 -334 -340 -342 ·-------­ - Table 5. Nutrient measurements in sample incubations. Nutrient units in µmole· r'. Missing values show with a period. Cores 4 and 5 are controls with just station water. Date STA Core Time P04 SI04 N02 N03 NH4 22APR92 GIG 1 10:20 0.721 141 0.412 0.924 1.960 22APR92 GIG 1 12:20 0.440 143 0.357 0.190 1.622 22APR92 GIG 2 10:20 0.693 141 0.456 0.151 2.507 22APR92 GIG 2 12:20 0.575 143 0.466 0.141 2.361 22APR92 GIG 3 10:20 0.687 141 0.354 0.435 1.819 22APR92 GIG 3 12:20 0.384 143 0.299 0.126 1.577 22APR92 GIG 4 10:20 0.409 142 0.194 1.080 2.202 22APR92 GIG 4 12:20 0.345 141 0.213 0.880 1.095 22APR92 GIG 5 10:20 0.370 142 0.198 0.955 2.131 22APR92 GIG 5 12:20 0.306 141 0.200 0.771 0.805 22APR92 GIS 1 10:20 0.289 141 0.236 0.006 22APR92 GIS 1 12:20 0.312 140 0.214 0.332 0.987 22APR92 GIS 2 12:30 0.424 140 0.256 0.169 1.310 22APR92 GIS 2 14:42 0.382 139 0.201 0.466 1.150 22APR92 GIS 3 12:30 0.418 140 0.227 0.319 1.198 22APR92 GIS 3 14:42 0.299 139 0.205 0.341 0.956 22APR92 GIS 4 12:30 0.433 141 0.264 0.404 1.251 22APR92 GIS 4 14:42 0.347 140 0.241 0.123 1.050 22APR92 GIS 5 12:30 0.503 140 0.267 0.461 1.318 22APR92 GIS 5 14:42 0.363 140 0.221 6.335 1.405 22APR92 Pl1G 1 14:52 1.019 138 0.804 5.752 4.504 22APR92 Pl1G 1 16:58 0.651 147 0.553 6.003 2.616 22APR92 Pl1G 2 14:52 1.143 137 0.807 5.748 3.775 22APR92 Pl1G 2 16:58 0.872 149 0.516 5.919 2.751 22APR92 P11G 3 14:52 1.006 136 0.803 5.753 22APR92 Pl1G 3 16:58 0.833 143 0.519 5.854 2.242 22APR92 Pl1G 4 14:52 0.576 134 0.807 5.810 7.476 22APR92 Pl1G 4 16:58 0.501 135 0.303 6.010 2.528 22APR92 Pl1G 5 14:52 0.461 137 0.255 6.300 0.848 22APR92 Pl1G 5 16:58 0.452 135 0.274 6.282 2.389 23APR92 BB6 1 10:33 2.972 168 0.410 0.554 18.640 23APR92 BB6 1 12:33 1.380 173 1.000 0.003 5.287 23APR92 886 2 10:33 2.017 166 0.279 0.454 7.971 23APR92 BB6 2 12:33 1.422 168 0.853 0.027 4.728 23APR92 B86 3 10:33 1.062 176 0.779 0.049 39.448 23APR92 BB6 3 12:33 1.741 173 1.074 0.118 8.376 23APR92 BB6 4 10:33 1.062 161 0.738 0.184 5.200 23APR92 BB6 4 12:33 1.125 160 0.681 0.172 3.924 23APR92 886 5 10:33 1.295 162 0.820 0.306 4.842 23APR92 886 5 12:33 1.019 159 0.705 0.133 3.781 23APR92 189G 1 13:18 1.847 159 0.500 0.433 22.794 23APR92 189G 1 15:18 1.168 160 0.861 0.002 6.455 23APR92 189G 2 13:18 2.123 159 0.402 0.300 21.775 23APR92 189G 2 15:18 1.146 157 0.828 0.020 6.542 23APR92 189G 3 13:18 1.613 161 0.549 0.464 9.125 23APR92 189G 3 15:18 1.125 162 0.787 0.047 5.034 23APR92 189G 4 13:18 0.828 160 0.385 0.288 2.060 23APR92 . 189G 4 15:18 0.807 158 0.312 0.400 1.689 23APR92 189G 5 13:18 0.764 185 0.320 0.448 1.472 23APR92 189G 5 15:18 0.764 156 0.262 0.327 1.302 23APR92 189S 1 15:28 1.231 157 0.713 0.079 4.045 23APR92 189S 1 17:28 0.807 155 0.361 0.362 2.855 23APR92 189S 2 15:28 0.934 157 0.312 0.358 2.681 23APR92 189S 2 17:28 1.062 153 0.640 0.069 4.435 23APR92 189S 3 15:28 0.828 156 0.459 0.197 3.457 23APR92 189S 3 17:28 1.062 152 0.451 0.352 3.905 23APR92 189S 4 15:28 0.807 157 0.262 0.271 0.873 23APR92 189S 4 17:28 0.637 156 0.295 0.711 1.148 23APR92 189S 5 15:28 0.828 157 0.287 0.232 0.888 23APR92 189S 5 17:28 0.722 155 0.295 0.806 1.120 24APR92 TSS 1 9:24 0.442 171 0.364 0.402 3.427 24APR92 TSS 1 11 :24 0.566 170 0.356 0.023 2.778 24APR92 TSS 2 9:24 0.365 172 0.395 0.199 2.596 24APR92 TSS 2 11 :24 0.501 172 0·.341 0.334 3.225 24APR92 TSS 3 9:24 0.392 171 0.372 0.208 2.738 24APR92 TSS 3 11 :24 0.447 171 0.354 0.150 3.265 24APR92 TSS 4 9:24 0.304 171 0.339 0.070 2.413 18 24APR92 TSS 4 11 :24 0.624 170 0.321 0.637 2.109 24APR92 TSS 5 9:24 0.366 171 0.333 0.060 3.650 24APR92 TSS 5 11 :24 0.502 170 0.334 0.296 2.150 24APR92 TPG 1 13:40 0.604 193 0.358 0.106 2.880 24APR92 TPG 1 15:40 0.544 194 0.451 0.093 2.718 24APR92 TPG 2 13:40 0.977 194 0.427 0.178 2.596 24APR92 TPG 2 15:40 0.698 194 0.483 0.046 2.738 24APR92 TPG 3 13:40 0.970 194 0.403 0.656 2.312 24APR92 TPG 3 15:40 0.529 194 0.376 0.138 1.987 24APR92 TPG 4 13:40 0.467 195 0.370 0.205 2.251 24APR92 TPG 4 15:40 0.430 194 0.352 0.147 1.825 24APR92 TPG 5 13:40 0.494 195 0.374 0.186 2.211 24APR92 TPG 5 15:40 0.514 194 0.430 0.054 2.434 24APR92 SKG 1 9:49 0.694 185 0.472 0.230 0.293 24APR92 SKG 1 11 :49 0.718 184 0.385 0.183 0.492 24APR92 SKG 2 9:49 0.775 185 0.467 0.221 0.670 24APR92 SKG 2 11 :49 0.624 184 0.295 0.193 0.377 24APR92 SKG 3 9:49 0.753 186 0.353 0.255 1.309 24APR92 SKG 3 11:49 1.114 186 0.376 0.303 0.817 24APR92 SKG 4 9:49 0.424 186 0.254 0.272 0.314 24APR92 SKG 4 11:49 0.406 185 0.269 0.329 0.440 24APR92 SKG 5 9:49 0.453 185 0.249 0.605 0.230 24APR92 SKG 5 11:49 0.558 185 0.374 0.143 0.900 27APR92 CPG 1 11:56 0.833 186 0.541 0.099 1.361 27APR92 CPG 1 13:56 0.703 186 0.579 0.030 1.288 27APR92 CPG 2 11:56 0.903 185 0.599 0.028 i.518 27APR92 CPG 2 13:56 0.620 184 0.489 0.074 i.204 27APR92 CPG 3 11 :56 0.677 185 0.500 0.046 1.413 27APR92 CPG 3 13:56 0.669 186 0.484 0.066 2.565 27APR92 CPG 4 11 :56 0.573 185 0.276 0.121 0.733 27APR92 CPG 4 13:56 0.412 185 0.283 0.049 1.926 27APR92 CPG 5 11 :56 0.520 185 0.279 0.105 0.722 27APR92 CPG 5 13:56 0.370 185 0.263 0.056 0.838 28APR92 GEN 1 9:28 0.766 182 0.503 0.035 ·1. 0·14 28APR92 GEN 1 11 :45 0.493 182 0.352 0.086 1.028 28APR92 GEN 2 9:28 2.145 182 0.490 0.042 3.714 28APR92 GEN 2 11 :45 0.716 182 0.401 0.098 1.455 19 28APR92 GEN 3 9:28 1.223 181 0.414 0.043 2.320 28APR92 GEN 3 11 :45 0.61 2 182 0.381 0.044 0.648 28APR92 GEN 4 9:28 0.680 181 0.347 0.036 0.957 28APR92 GEN 4 11 :45 0.468 180 0.3 13 0.105 0.395 28APR92 GEN 5 9:28 0.494 181 0.271 0.105 0.652 28APR92 GEN 5 11 :45 0.466 180 0.222 0.258 0.446 28APR92 Pl2G 1 12:01 0.485 171 0.224 0.249 0.455 28APR92 Pl2G 1 14:01 0.509 171 0.237 0.204 0.395 28APR92 Pl2G 2 12:01 0.617 175 0.391 0.144 0.851 28APR92 Pl2G 2 14:01 0.650 178 0.381 0.122 1.618 28APR92 P12G 3 12:01 0.554 175 0.308 0.221 0.410 28APR92 P12G 3 14:01 0.557 176 0.352 0.144 0.800 28APR92 P12G 4 12:01 0.389 171 0.076 0.378 0.607 28APR92 Pl2G 4 14:01 0.557 176 0.352 0.144 0.800 28APR92 Pl2G 5 12:01 0.408 172 0.109 0.406 0.271 28APR92 Pl2G 5 14:01 0.380 171 0.115 0.300 0.923 24APR92 TSG 1 11:34 0.521 172 0.379 0.221 2.697 24APR92 TSG 1 13:34 0.423 172 0.422 0.117 2.555 24APR92 TSG 2 11 :34 0.460 172 0.439 0.019 3.123 24APR92 TSG 2 13:34 0.369 174 0.380 0.145 2.312 24APR92 TSG 3 11 :34 0.502 171 0.420 0.634 3.407 24APR92 TSG 3 13:34 0.488 171 0.457 0.052 2.839 24APR92 TSG 4 11 :34 0.610 172 0.396 0.486 2.758 24APR92 TSG 4 13:34 0.320 171 0.323 0.015 2.129 24APR92 TSG 5 11 :34 0.349 173 0.335 0.063 2.393 24APR92 TSG 5 13:34 0.324 171 0.336 2.2i 1 0. il~.3 Table 6. Oxygen measurements in sample incubations. Oxygen units in µmole·r'. Missing values show with a period. Core 4 is a control with just station water. Date Station Time Core 1 Core 2 Core 3 Core 4 22APR92 GIG 10:25 213.9 277.9 359.9 311 .2 22APR92 GIG 10:40 183.9 251.0 361.4 347.9 22APR92 GIG 10:55 163.3 226.4 328.9 344.4 22APR92 GIG 11 :10 160.9 201.7 310.4 343.7 22APR92 . GIG 11 :25 129.8 163.4 281 .1 341.5 22APR92 GIG 11 :40 104.4 151.0 21 5.6 338.3 22APR92 GIG 11 :55 102.8 132.6 222.9 339.2 22APR92 GIG 12:10 109.3 126.8 204.9 336.9 22APR92 GIS 12:40 304.3 356.9 446.2 400.4 22APR92 GIS 12:55 263.5 352.8 457.9 402.8 22APR92 GIS 13:10 281.0 357.4 456.5 404.7 22APR92 GIS 13:25 287.5 373.1 474.0 406.4 22APR92 GIS 13:40 299.6 381.0 482.4 405.7 22APR92 GIS 13:55 292.7 379.5 481.4 404.8 22APR92 GIS 14:10 285.1 375.6 471 .5 402.6 22APR92 GIS 14:40 246.0 365.7 459.4 398.3 22APR92 Pl1G 14:55 313.6 317.6 434.3 -'380.4 22APR92 Pl1G 15:10 236.8 220.2 329.8 390.i 22APR92 Pl1G 15:25 176.1 131.0 231.6 395.5 22APR92 P11G 15:40 114.3 63.2 162.1 398.5 22APR92 Pl1G 15:43 87.5 37.3 127.5 399.5 22APR92 Pl1G 15:47 78.8 25.8 125.0 399.9 22APR92 P11G 16:02 40.8 0.1 111.4 400.3 23APR92 886 10:42 178.7 279.3 343.1 342.8 23APR92 886 11 : 12 160.0 263.4 330.7 339.0 23APR92 886 11 :27 160.0 260.5 294.7 335.4 23APR92 886 11 :42 159.4 259.2 303.7 333.1 23APR92 886 11 :57 160.3 260.3 315.7 331 .8 23APR92 886 12:12 157.3 242.8 313.4 332.4 23APR92 886 12:27 153.5 21 7.3 292.0 333.9 23APR92 189G 13:27 305.7 343.8 443.8 382.9 23APR92 189G 13:42 260.4 296.3 412.4 382.8 23APR92 189G 13:57 177.3 251.3 370.8 382.2 23APR92 189G 14:12 120.4 243.9 290.8 381 .5 23APR92 189G 14:27 48.3 243.6 210.7 380.7 23APR92 189G 14:42 40.9 190.1 143.6 380.4 23APR92 189G 14:57 10.1 159.5 128.6 380.7 23APR92 189G 15:12 0.0 162.0 123.2 379.8 23APR92 189S 15:27 278.7 346.7 457.2 379.0 23APR92 189S 15:42 256.5 344.7 441.4 378 .5 23APR92 189S 15:57 252.5 344.1 437.7 378.3 23APR92 189S 16:12 242.8 338.6 430.8 377.4 23APR92 189S 16:27 234.7 337.4 428.9 377.4 23APR92 189S 16:42 227.8 323.5 422.5 376.4 23APR92 189S 16:57 213.7 312.9 408.3 375.1 23APR92 189S 17:12 208.0 310.2 400.2 374.6 24APR92 TSS 9:30 97.3 195.8 291 .9 285.1 24APR92 TSS 9:45 85.5 174.8 282.i 280.0 24APR92 TSS 10:00 76.2 165.7 256.8 275.1 24APR92 TSS 10:15 70.8 138.7 26Q.tl. 275.2 24APR92 TSS 10:30 67.1 141.9 2L'~Q . 0 ~::/-·.8 24APR92 TSS 10:45 64.9 134.0 227.7 270.0 24APR92 TSS 11 :00 65.9 140.2 223.4 280.3 24APR92 TSS 11 :15 58.6 147.4 214.7 281 .4 24APR92 TSG 11 :30 181.0 265.7 380.2 337.3 24APR92 TSG 11 :45 96.8 142.2 260.9 342. 1 24APR92 TSG 12:00 92.1 104.3 219.3 339.9 24APR92 TSG 12:30 32.1 54.5 182.8 329.9 24APR92 TSG 12:45 24.4 32.8 155.1 328.2 24APR92 TSG 13:00 31. 6 19.6 146.7 327.9 24APR92 TSG 13:15 37.6 20.5 148.9 325.8 24APR92 TSG 13:30 27.4 19.7 145.7 325.4 24APR92 TPG 13:45 182.7 314.7 412.2 367.5 24APR92 TPG 14:00 111.3 280.0 221.3 364.6 24APR92 TPG 14:15 42.4 230.3 124.1 362.1 24APR92 TPG 14:30 23.6 175.5 122.2 358.5 24APR92 TPG 14:45 21.5 115.4 149.8 353.1 24APR92 TPG 15:00 13.0 76.0 138.7 349.9 24APR92 TPG 15:15 3.6 55.2 97.2 348.0 24APR92 TPG 15:30 0.0 39.3 73.5 345.4 27APR92 SKG 9:54 299.6 368.5 445.0 395.9 27APR92 SKG 10:09 218.2 263.0 351.5 391.3 27APR92 SKG 10:24 148.7 177.6 273.9 387.2 27APR92 SKG 10:39 77.8 125.8 176.7 382.6 27APR92 SKG 10:54 35.5 114.1 120.1 379.5 27APR92 SKG 11 :09 16.4 97.4 77.8 378.7 27APR92 SKG 11 :24 6.7 76.4 51.2 376.5 27APR92 SKG 11 :39 9.8 50.5 36.7 374.3 · 27APR92 CPG 11 :54 310.2 369.7 482.2 397.5 27APR92 CPG 12:09 197.6 317.1 425.5 399.7 27APR92 CPG 12:24 188.7 293.3 407.3 401.8 27APR92 CPG 12:39 184.8 282.9 381 .8 401.6 27APR92 CPG 12:54 188.5 272.2 368.0 397.3 27APR92 CPG 13:09 160.3 258.3 346.9 39S.1 27APR92 CPG 13:24 151.8 250.5 325.2 393.3 27APR92 CPG 13:39 66.4 235.9 311.6 391.6 27APR92 CPG 13:54 52.7 216.0 297.9 390.0 28APR92 GES 9:36 214.4 278.8 397.3 363.9 28APR92 GES 9:51 198.3 256.8 390.5 362.4 28APR92 GES 10:06 201.8 247.4 378.8 359.8 28APR92 GES 10:21 200.1 242.8 382.5 358.0 28APR92 GES 10:36 201 .0 239.7 373.4 356.0 28APR92 GES 10:51 199.8 243.0 370.7 353.3 28APR92 GES 11 :06 28APR92 GES 11 :21 28APR92 GES 11:36 28APR92 Pl2G 12:06 28APR92 P12G 12:21 28APR92 Pl2G 12:36 28APR92 Pl2G 12:51 28APR92 P12G 13:06 28APR92 P12G 13:21 28APR92 Pl2G 13:36 28APR92 Pl2G 13:51 195.1 188.0 182.8 283.8 222.3 174.9 132.0 148.9 121.4 107.4 86.8 230.6 227.8 232.7 297.8 205.8 133.8 94.5 78.5 56.8 41.1 25.1 373.4 348.9 371.5 345.5 369.8 343.4 441.3 399.3 373.1 402.6 317.3 401.1 242.1 399.3 249.4 394.2 225.9 390.9 172.0 386.3 138.7 384.7 24