Assessment of the contaminant concentration variability among Lake Geneva Arctic char using stable isotopic composition (delta15N and delta13C).

Abstract

Measurements of organochlorine [polychlorinated biphenyls (PCBs) and dichloro-diphenyl-dichloroethylene (DDE)] and Hg concentrations and nitrogen and carbon stable isotopic compositions (delta15N and delta13C) were performed on 63 Arctic char (Salvelinus alpinus) from Lake Geneva. Fish exhibited a high interindividual variablity in pollutant concentrations. Since the accumulation of such persistent contaminants is obtained from food, the co-occurrence of dietary differentiation leading to the contaminant interindividual variability was suspected. delta15N and delta13C were used for assessing trophic position and food source differences among Arctic char. The low ranges of delta15N and delta13C could not explain the interindividual variability in pollutant concentrations. The lack of relation between delta15N and contaminant concentration did not suggest a trophic level biomagnification of PCB, DDE, and Hg. Lake Geneva spatial variability in pollutants may be an important factor of variability within the Arctic char population. The bioaccumulation pattern occurring for Hg was not apparent for PCB and DDE. Organochlorines are hydrophobic contaminants, and their bioaccumulation pattern may be masked by seasonal variations in fish lipid content.