Oxidative and osmoregulatory effects of imidacloprid, cadmium, and their combinations on Daphnia magna.

Oxidative stress and osmoregulatory system damage-inducing potential of binary mixtures of neonicotinoid insecticide imidacloprid (IMI) and Cd2+ in Daphnia magna were evaluated. Animals were subjected to subchronic (7 days) and acute (48 h) of IMI and Cd2+ effects with single and binary mixtures. ATPase and antioxidant enzyme activities with lipid peroxidation were measured. Morphometric characteristics were also evaluated. Response patterns showed variability due to the duration, concentration, and toxicant type. While the enzyme activities mostly showed a decreasing trend upon the subchronic IMI effect, there was an increasing trend after the Cd2+. Declined enzyme activities were more pronounced with the acute higher IMI+Cd2+ exposure. Ca2+-ATPase and CAT were the most sensitive biomarkers in the toxicity response. IMI+Cd2+ exposures are appeared to increase their toxic effects due to their oxidative potential. ATPase inhibition and antioxidant enzyme alterations with a decrease in morphometric characteristics in Daphnia even at their low concentrations of IMI and Cd2+ show evidence of their toxicities on aquatic life. It was emphasized that investigating the combined effects of toxicants at their environmental level based on the multi-biomarker approach is essential in toxicity evaluation.