Factors that influence the accumulation of copper and cadmium by transplanted eastern oysters (Crassostrea virginica) in the Patuxent River, Maryland

To investigate the continued accumulation of copper and cadmium by oysters in the Patuxent River, MD, which have been at high levels since at least the mid 1960s, hatchery-raised Eastern oysters were transplanted into trays at four sites in the upper estuary. At each site two groups of oysters were used to determine growth and mortality, and another group was sampled for meat condition, metal concentration and body burden. Copper in oysters in the discharge of a coal-fired power plant was significantly greater than at all other sites, but maximum concentration of 310 micrograms g-1 was well below the maximum of 1880 micrograms g-1 detected in 1982. Cadmium levels were also significantly greater in the discharge than at the other sites, but probably because of higher discharge temperatures. Trace metal loadings, the local salinity gradient and the higher temperatures caused by power plant operation all appear to contribute to metal accumulation by oysters in the upper Patuxent estuary.