LABORATORY STUDY OF CD AND HG UPTAKE BY 2 FRESH-WATER MOLLUSKS IN RELATION TO CONCENTRATION, AGE AND EXPOSURE TIME

To assess the potential of two molluscs species as bioindicators of Cd and Hg pollution in aquatic ecosystems, a laboratory study was conduc ted on the short-lived gastropod Viviparus georgianus and the pelecypo d Elliptio complanata. Using analysis of covariance (ANCOVA), we have evaluated the contribution of the aqueous trace metal concentration, t he size of the molluscs and the exposure time to explain the Cd and Hg body concentration. Results show that all the parameters analyzed hav e a significant effect on Cd and Hg body variation in the gastropod ex cept for the time of exposure and the interaction time of exposure-hei ght of the individuals. The same results are observed for the pelecypo d, except that the length of the individuals has not a significant inf luence on Cd and Hg variation. The major part of the variability of th e body metal concentration seems to be explained by these three parame ters: the water metal concentration, the interaction of water metal co ncentration with time of exposure and the interaction of water metal c oncentration with time of exposure and the size of the individuals.