A COMPARATIVE-STUDY ON THE RELATION BETWEEN COPPER AND CONDITION IN MARINE BIVALVES AND THE RELATION WITH COPPER IN THE SEDIMENT

The relation between condition and copper concentration was assessed i n three bivalve species (the Baltic clam Macoma balthica, the cockle C erastoderma edule and the mussel Mytilus edulis) from several Dutch an d French estuaries. In general, the copper concentration in the bivalv es was negatively related to condition. The slope of this relation was strongest in the Baltic clam M. balthica, with an almost inversely pr oportional change of Cu concentration at a change of condition, indica ting an almost constant Cu content (body burden) per individual, i.e. no elimination or accumulation of Cu. In the mussel M. edulis, the slo pe of this relation was absent or the weakest, with an almost uniform Cu concentration at a change of condition, indicating an almost propor tional elimination (or accumulation) of Cu at a decrease (or increase) of the condition. Thus in Baltic clams the copper body burden is kept at an almost constant level, whereas in mussels the copper concentrat ion is almost constant. In Baltic clams, but not in mussels and cockle s, spatial differences were related to copper concentrations in the se diment. It is discussed that mussels maintain a homeostatic Cu concent ration within a short time-period (days; copper highly exchangeable by complexation to metallothioneins), whereas the Cu concentration in Ba ltic clams is more slowly regulated (several weeks; fossilization of c opper in mineral granules) and remains on an average in (partitioning) equilibrium with the Cu concentration in the sediment. Therefore, the Baltic clam is a better indicator of sediment copper pollution than t he commonly used mussel. In addition, the observed differences between species were compared with differences in their life-strategies. The Cu concentration in the sediment is strongly related to the silt fract ion (<16 mu m) of the sediment.