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(022) The metal biomonitor Chaoborus: Increases in lakes recovering from smelter emissions? Croteau, Marie-Noële1, Hare, Landis1, Tessier, André1, 1 ABSTRACT- Animals can be used as biomonitors to estimate pollution levels in ecosystems provided that an appropriate model is available to relate pollutant concentrations in animals to those in their surroundings. Such a model, grounded in biological and chemical theory, has been developed to relate Cd concentrations in lakewater to those in the predatory insect Chaoborus provided that competition between hydrogen ions and cadmium ions for biological uptake sites is taken into account. We tested the utility this biomonitor for measuring temporal changes in bioavailable Cd in lakes to which anthropogenic emissions have declined during the past decade. We show that in most lakes declines in dissolved Cd concentrations are directly related to Cd declines in Chaoborus larvae. However, in a few lakes, Cd levels in Chaoborus increased as aqueous Cd levels declined. This apparent contradiction can be explained by considering parallel declines in lakewater acidity using our bioaccumulation model. The results of our study suggest that, although the response of metal concentrations in animals to changes in aqueous metal concentrations can be complex, such changes can be understood through the use of a theoretically-based model. We conclude that Chaoborus larvae can be effective biomonitors of both temporal and spatial changes in Cd bioavailability in lakes. Key words: biomonitor, cadmium, Chaoborus, recovery |
