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(357) Causes of Sediment Toxicity in Grizzly Bay, California.
Phillips, Bryn*,1, Anderson, Brian1, Hunt, John1, Nicely, Patricia1, Tjeerdema, Ronald1, Sericano, Jose2, Thompson, Bruce3, Hoenicke, Rainer3, 1 University of California, Davis, Monterey, CA, USA2 Texas A&M University, College Station, TX, USA3 San Francisco Estuary Institute, Oakland, CA, USA
ABSTRACT- Sediment toxicity has been monitored in San Francisco Bay as part of the Regional Monitoring Program since 1993. Amphipod (Eohaustorius estuarius) and bivalve (Mytilus galloprovincialis) toxicity test data are combined with chemical and physical data to determine sediment quality in the estuary. Toxicity to amphipods and bivalve embryos has been observed in sediments from Grizzly Bay. Sediments from this station are consistently contaminated by moderate concentrations of a mixture of trace metal and trace organic chemicals. Causes of toxicity were investigated using a weight-of-evidence approach combining correlation analyses, chemical measurements in sediment, sediment elutriate, pore water, and amphipod tissues, and Toxicity Identification Evaluations (TIEs). TIEs with developing bivalve embryos indicated that toxicity of sediment elutriate was due to cationic metals. Experiments conducted to separate cationic metals in sediment elutriates determined that copper was primarily responsible for embryo toxicity. Amphipod mortality was weakly correlated with sediment zinc, chromium, chlordane, and mixtures of bulk-phase chemicals characterized as mean Effects Range Median Quotients. Toxicity tests demonstrated that amphipod mortality was greater in whole-sediment exposures than in pore water exposures, suggesting contaminant uptake via sediment ingestion rather than respiration. Information from solid-phase TIEs combined with measures of trace organic tissue concentrations in sediment-exposed amphipods suggest that non-polar organic compounds were probably not the primary cause of acute toxicity. Amphipod toxicity was eliminated when sediment was subjected to a weak acid leach. Chemical analyses of samples from various treatments suggest this was a result of reduction in metal loading of Grizzly Bay sediment.
Key words: sediment, elutriate, toxicity identification evaluation, metals
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