COPPER IN INDIGENOUS AND TRANSPLANTED ZEBRA MUSSELS IN RELATION TO CHANGING WATER CONCENTRATIONS AND BODY-WEIGHT

Zebra mussels, Dreissena polymorpha, were collected monthly from a cop per-contaminated reservoir over a period of nearly 3 years. Copper con centrations in the organisms showed marked fluctuations reflecting cha nges in the water contamination. Bioconcentration patterns were influe nced by the specific capacity of this sentinel organism to biologicall y integrate the continuously evolving water pollution; the sampling pa ttern, which inevitably introduced a certain subjectivity into monitor ing results; and weight changes in the animals within the yearly cycle . Consequently, the successive monthly indications obtained with the z ebra mussels provided a current biological assessment of a complex dyn amic contamination situation. In a second experiment, caged mussels fr om three different populations were transferred for 3 months into the reservoir and sampled on six occasions. Mortality rates, attachment ca pacity, and a condition index revealed no substantial fitness disturba nces in the transplanted organisms. Differences in dry weight througho ut the experiment were attributable to the initial characteristics of each population. The influence of body mass on monitoring results was eliminated by replacing copper concentrations (mu g/g dry weight) with copper burdens (mu g/specimen). In terms of copper burdens, the three transplanted populations exhibited very similar metal patterns. Moder ate quantitative differences between introduced and indigenous populat ions were interpreted as the result of physiological adaptation of the indigenous mussels to their contaminated environment. This study show ed that the transfer technique with D. polymorpha is a useful tool for active biomonitoring programs.