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(M/EH129) Acclimation of Daphnia magna to different background concentrations of copper. Bossuyt, Bart1, Janssen, Colin1, 1 ABSTRACT- The ultimate aim of ecotoxicological studies is to predict how natural populations respond to contaminant exposure. It is often assumed that laboratory and field organisms respond identically towards metal exposure. Various authors have identified acclimation and adaptation as factors that may cause laboratory-reared and field-collected organisms to react differently towards toxicants, since laboratory tests are conducted with non-acclimated (to metal background concentrations) organisms. In this study we compared the copper tolerance of Daphnia magna cultured in 4 different background concentrations of copper during several months. The background concentrations used were 1, 5, 12, 35 Key words: acclimation, copper, background, Daphnia magna |
g/l Cu (total) and were prepared in a modified M4-medium (Elendt and Bias, Water Research, 24(9), 1157-1167, 1990) in which 5 mg/l dissolved organic carbon, as a substitute for EDTA, was added and the hardness was reduced to 180 mg/l as CaCO3. These background concentrations correspond to bioavailable copper concentrations of 2, 11, 28 and 95 pg/l Cu2+. The copper tolerance was monitored using endpoints at different levels of biological organisation (acute toxicity, reproduction and energy budgets). For the moment, the acute and chronic experiments of the first and second generation give no indication of a differential acclimation to these background concentrations. Experiments with the subsequent generations are ongoing. It is hypothesized that organisms exposed to higher (bioavailable) background concentrations of copper, will exhibit a reduced copper sensitivity. The importance of acclimation to different copper background concentrations of resident species will be discussed in the context of environmental risk assessment procedures.