Individual and Joint Toxicity of Three Chloroacetanilide Herbicides to Freshwater Cladoceran Daphnia carinata

Individual and joint toxicity of three chloroacetanilide herbicides to a freshwater cladoceran were studied. The 48 h-LC 50 values of alachlor, acetochlor and butachlor to Daphnia carinata Dc42 were 11.1, 11.8 and 3.45 mg L −1 , respectively. The toxicity was significantly ( p < 0.05) related to hydrophobicity. The additive indexes of binary mixtures of three herbicides were less than zero and it showed antagonism. The body length of D. carinata treated with high concentration of herbicides was shorter than that of control group significantly ( p < 0.05). It suggests that joint actions must be considered when assessing the acute toxicity of chloroacetanilide herbicides to D. carinata .