Ecotoxicology of the Eurasian Otter (Lutra lutra) along Loire River (France) and Predictable Trends due to Global Change

In this study, about fifty otters from the basin of the Loire River (France) were analyzed in the context of a toxicological study funded by the Plan Loire Grandeur Nature. Individuals were recovered non-invasively, using a network of collection of otters killed by traffic collisions with vehicles. The chemical elements analyzed were the organochlorine and organophosphorus pesticides, carbamates, pyrethroids, herbicides, anticoagulants, PCBs and metals. Detectable levels of organochlorine pesticides and PCBs characterized all otters analyzed, with mean values reaching 2-15 mg kg-1, respectively. Concentrations of other analyzed pesticides remained very low. For metals, contamination of otters was systematic for lead and mercury, the latter being relatively abundant in tissues of several individuals. A significant trend to increasing concentrations of pesticides and PCBs by going towards the downstream parts of basins was shown. The inter-individual variations in concentrations were marked. Global values of contamination were below the toxicological threshold defined for the conservation of the species, and the current dynamics of populations within the basin of the Loire seems to confirm this. However, the potential effects of mixtures of compounds remain poorly studied.