THE INFLUENCE OF SEDIMENT, FOOD AND ORGANIC-LIGANDS ON THE UPTAKE OF COPPER BY SEDIMENT-DWELLING BIVALVES

The sediment-dwelling bivalve Macoma balthica was exposed to dissolved copper ina flow-through system in long-term experiments. Unlike anoth er sediment-dwelling bivalve, the suspension feeder Cerastoderma edule (cockle), M. balthica accumulated copper from the sediment, while the cockles did not. When dwelling in silty, organic-rich sediment, M. ba lthica accumulated less from the water, whereas accumulation in the co ckle was not influenced by the sediment type. In water from the Ooster schelde sea-arm, total organic ligand concentrations were around 100 n anoequivalent copper, with a free Cu2+ concentration of 6.3 x 10(-14) M (pCu 13.20). Addition of 400 nM Cu (25 mu g l(-1)) resulted in a fre e Cu2+ concentration of 2.19 x 10(-8) M (pCu 7.66); Addition of low co ncentrations of EDTA caused a reduction of Cu uptake, which was confir med with the calculated cupric ion activity. In water with 400 nM Cu, M. balthica accumulated more copper when fed on copper-enriched algae than without the addition of the algae. This accumulation occurred des pite a decrease in filtration rates and indicates an important contrib ution of food-associated copper to the overall accumulation by Macoma balthica.