The persistence of IXTOC-I oil along the South Texas coast




Amos, Anthony F.

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The ongoing study, initiated in April 1978, monitors the bird population utilizing this stretch of Gulf coast beach along with sea and weather conditions, beach profile measurements, demographic trends in this rapidly developing area, and the types of beach debris, natural and man-made, including oil and tarballs. The survey is now done on alternate days, and at this writing, 665 have been completed covering 8,000 km of beach, taking 1300 man-hours; 700,000 individual birds of 204 species have been counted. The survey is done by automobile, and distances are measured using a calibrated odometer with a repeatability of 0.03 km to known landmarks. The location of all tar-reefs along the beach has been monitored since 1979. Due to seasonal variations in sea level the tar-reefs remain submerged for much of the year. From late November through February low tides expose the reefs, but at the same time the passage of winter "northers" creates energetic wave systems which erodes them. Fields of characteristic tarballs eroded from the reefs are washed onto the beach and remain there until buried by sand or washed into the foredunes during storms. Figure 17 shows the location of reefs and tarball fields associated with the reefs from September 1979 through June 1983. The last period when the reefs were exposed (in early 1983) revealed several small reefs, the largest being 25 m long by 3 m wide by 25 cm thick, and many tarball fields. It should be noted that due to the limited resources and time available for this project, no effort has been made to locate the tar-reefs when they are submerged. Tar-reef and tarball samples have been collected at intervals throughout the study period and are preserved frozen at UT-MSIP A.