Bioaccumulation of heavy metals in oyster (Crassostrea virginica) tissue and shell

Oysters and sediment have been collected from most major US Gulf of Mexico bays and estuaries each year since 1986. Selected samples of oyster soft ti ssue, shell and sediments were analyzed for Cd, Cr, Cu, Fe, Mn, Pb, and Zn for this study. Concentrations varied considerably from place to place but ratios of metals remained relatively constant. Cu and Zn are greatly enrich ed in oyster tissues, which is related to their physiological function. Cd is enriched in oyster shell because of the easy substitution between Cd and Ca. The concentrations of Pb and Cr in oysters are significantly lower tha n that in sediment, suggesting a good discrimination against these metals b y oysters. Metal variations are a result of both nature and human activity.