Trace elements in Gulf of Mexico oysters, 1986-1999
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As part of the National Oceanic and Atmospheric Administration (NOAA) Status and Trends Mussel Watch Program, oysters (Crassostria virginica) have been sampled along the entire US Gulf of Mexico (GOM) coastline once each year since 1986. The same sampling sites were reoccupied each year when possible. As a result, 63 different sites were sampled for at least 7 of the years between 1986 and 1999. Concentrations of Ag, As, Cd, Cu, Hg, Se, Pb and Zn in these oysters are reported here. The data show considerable variation for all metals, with the site-to-site variation generally larger than year-to-year variation at a given site. Metal concentrations at some sites were either much higher or much lower than average GOM concentrations year after year. At other sites metal concentrations decreased or increased for several years in a row and then reversed this trend. Large differences were often found at sites only 10 km or so apart, showing local control of metal concentrations. Only in a few cases can reasons for these differences be suggested, but because several metals commonly followed the same trend at a given site, both natural and human influences are suspected. Mercury concentrations were high near an old chlor-alkali plant, Zn was high near industrial areas and harbors and Pb was high on an Air Force Base. Arsenic concentrations were higher at open water sites than at back bay sites, especially in Florida, possibly due to differences in dissolved phosphate concentrations. Cd and Se concentrations were generally higher in Texas and Louisiana than in Florida but the opposite was true for As and Hg. 2004 Elsevier B.V. All rights reserved.
