Comparative toxicity of imidacloprid and its transformation product 6-chloronicotinic acid to non-target aquatic organisms: Microalgae Desmodesmus subspicatus and amphipod Gammarus fossarum

Neonicotinoids are widely applied pesticides due to their higher affinity for insect nicotinic acetylcholine receptors. These compounds are extensively applied to control pest insects in different agricultural crops; however they can also affect non-target invertebrates. Little is known about the toxicity effects of their transformation products on aquatic non-target organisms. Oxidative stress responses and behavioural changes in the crustacean amphipod Gammarus fossarum were investigated as well as the growth rate in freshwater algae Desmodesmus subspicatus after 96 h exposure to imidacloprid, its commercial formulation Confidor 200SL and its transformation product 6-chloronicotinic acid. Algal growth has shown significant sensitivity to Confidor 200SL and 6-chloronicotinic acid when compared to imidacloprid. In the case of amphipods, low doses of imidacloprid (102.2 mu g L-1) were sufficient to induce lipid peroxidation, while Confidor 200SL induced increased catalase activity (511.3 mu g L-1) and lipid peroxidation (255.6 mu g L-1). 6-Chloronicotinic acid altered significantly only antioxidant mechanisms (catalase activity) without changing lipid peroxidation levels. These different biochemical responses are helpful to understand the mechanism of imidacloprid and 6-chloronicotinic acid-induced oxidative stress. In addition, obtained data demonstrate potential harmful effects of neonicotinoid-based pesticides on non-target aquatic organisms. (c) 2012 Elsevier Inc. All rights reserved.