Toxic effects of environmentally realistic concentrations of diclofenac in organisms from two distinct trophic levels, Hediste diversicolor and Solea senegalensis

The use of pharmaceutical drugs has systematically increased, resulting in their environmental presence and exertion of effects on non-target aquatic organisms. Diclofenac (DCF) is an analgesic, anti-inflammatory and antipyretic drug, frequently found in the aquatic compartment. The present work analyzed the ecotoxicological effects of DCF in the marine polychaete Hediste diversicolor and in the marine fish Solea senegalensis. In addition, the putative toxic effects of DCF along a simulated food chain were studied, by feeding individuals of S. senegalensis with H. diversicolor previously exposed to DCF. Biomarkers of anti-oxidant defense (catalase, CAT), phase II metabolism (glutathione S-transferases, GSTs) and neurotoxicity (acetylcholinesterase, AChE) were quantified. The obtained results demonstrated that DCF did not affect CAT activity in organisms of both species directly exposed through the water, suggesting the absence of oxidative effects. In addition, organisms directly or indirectly exposed to DCF showed an increase of GSTs activities, suggesting an additional challenge to the metabolism of the exposed individuals. However, significant decreases in the activities of CAT and AChE were observed in fish fed with worms previously exposed to DCF. These data suggest that direct or indirect exposure to DCF may cause significant physiological modifications in aquatic organisms. In addition, exposure of wild organisms via contaminated food may lead to toxicological effects which may differ from alterations elicited by direct exposure. Such toxicological differences, between direct (waterborne) and trophic (via contaminated feed) exposures were qualitatively distinct, and need to be fully addressed when considering the consequences of environmental contamination by therapeutic drugs.