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(70-58) Influence of multi-generation acclimation to copper on tolerance, energy reserves and homeostasis of Daphnia magna. Bossuyt, Bart*,1, Janssen, Colin1, 1 Laboratory of Environmenal Toxicology and Aquatic Ecology, Ghent University, Gent ABSTRACT- The optimal concentration range for an essential element (OCEE) is determined by (1) the natural bioavailable background concentration range of the element in the species' natural habitat and (2) by the species' homeostatic capacity. In this study we assessed the ability of the freshwater crustacean Daphnia magna to acclimate to different bioavailable background concentrations of copper and established the OCEE of D. magna using physiological and population level test endpoints. An increase with factor 4 in acute copper tolerance was observed in daphnids acclimated tot 5150 pM Cu2+ compared to those cultured in < 10 pM Cu2+. Daphnids returned to a medium without copper addition (< 10 pM Cu2+) lost their increased tolerance, indicating an acclimation process and not adaptation. Determination of the energy reserves in the acclimated daphnids, revealed a broadening of the optimal copper concentration from 100-270 pM Cu2+ to 20-1000 pM Cu2+ during the acclimation period. Homeostactic copper regulation was observed up to 270 pM Cu2+. Implications of this research for both the culturing of Daphnia magna and the environmental risk assessment of metals will be discussed. Key words: copper, acclimation, Daphnia magna, background concentration |
