Effects of inorganic complexing on the toxicity of copper to Daphnia magna

Effects of carbonate-bicarbonate, orthophosphate, and pyrophosphate on the toxicity of copper (II) to Daphnia magna were studied at constant pH and total hardness. Mortality rates and reciprocal survival times were directly correlated with cupric (Cu²⁺) and copper hydroxy (Cu(OH)n) ion activities as determined by equilibrium calculations. Toxicity was negatively related to activities of soluble copper carbonate (CuCO₃) and other complexes, and was found to be independent of dissolved copper or total copper concentrations.