Copper bioavailability to marine bivalves and shrimp: Relationship to cupric ion activity

Studies were performed to determine the effects of dissolved substances present in natural seawater and sediment on the bioavailability of added Cu⁺². Whole clams Macoma inquinata and shrimp, Pandalus danae, were exposed to four concentrations of Cu in a flow-through seawater system. Bioaccumulation of Cu was reduced in shrimp, Pandalus danae, clams, M. inquinata, and excised clam gills, Protothaca staminea, exposed to an aged, compared with an unaged, Cu-seawater solution. This is thought to be due to slow complexation of the Cu by dissolved substances present in natural seawater. In a static system, with added sediment, more than 50% of the added Cu⁺² became bound to the organic fraction of the sediment and was unavailable to suspension feeding clams, Protothaca staminea. In contrast, deposit feeding clams, Macoma inquinata, placed in the sediment approximately doubled in Cu body burden within two months.Complexed Cu appears to be less bioavailable than ionic Cu and hence measurements of ionic and weakly complexed Cu by differential pulse anodic stripping voltametry provide a better prediction of bioavailable Cu than conventional measurements of total Cu-seawater concentrations.