Toxicity and bioavailability of the organophosphorus insecticide pirimiphos methyl to the freshwater amphipod Gammarus pulex L. In laboratory and mesocosm systems

Insecticides must be tested to determine their nontarget toxicity when released into the environment. Currently, new insecticides registered in Europe are likely to be tested, at the highest tier, in microcosms or mesocosms, although the costeffectiveness of these systems has yet to be established. This study investigated the effects of the organophosphorus insecticide pirimiphos methyl on the amphipod Gammarus pulex L. in 250-ml laboratory beakers and 50,000-L pond mesocosms. Acetylcholinesterase activity and survival were used as indicators of the insecticide's bioavailability and toxicity. The results from beakers and mesocosms were indistinguishable, indicating that the former are efficient tools for predicting the bioavailability of chemicals such as pirimiphos methyl that have high toxicity but low persistence in the environment.