Individual and combined toxicity of Cu~(2+),Cd~(2+) and Se~(4+) to Daphnia magna

We addressed the individual and combined toxicity of Cu2+,Cd2+ and Se4+ to Daphnia magna with a static test method.We also employed additive index method to evaluate their combined toxicity.Individual toxicity experiment shows that the toxicity of Cu2+,Cd2+ and Se4+ is degressive.Combined toxicity experiment shows that complex toxicity effect exhibits for different concentration ratios of Cu2+,Cd2+ and Se4+.Especially,the combined toxicity effect changed from antagonistic response to synergistic response with the increase of exposure time for equal concentration ratio of Cu2+ and Cd2+.