Assessment of the contaminant concentration variability among Lake Geneva arctic char using stable isotopic composition (delta N-15 and delta C-13)

Measurements of organochlorine [polychlorinated biphenyls (PCBs) and dichlo rodiphenyl-dichloroethylene (DDE)] and Hg concentrations and nitrogen and c arbon stable isotopic compositions (delta N-15 and delta C-13) were perform ed on 63 Arctic char (Salvelinus alpinus) from Lake Geneva. Fish exhibited a high interindividual variablity in pollutant concentrations. Since the ac cumulation of such persistent contaminants is obtained from food, the cc-oc currence of dietary differentiation leading to the contaminant interindivid ual variability was suspected. delta N-15 and delta C-13 were used for asse ssing trophic position and food source differences among Arctic char. The l ow ranges of delta N-15 and delta C-13 could not explain the interindividua l variability in pollutant concentrations. The lack of relation between del ta N-15 and contaminant concentration did not suggest a trophic level bioma gnification of PCB, DDE, and Hg. Lake Geneva spatial variability in polluta nts may be an important factor of variability within the Arctic char popula tion. The bioaccumulation pattern occurring for Hg was not apparent for PCB and DDE. Organochlorines are hydrophobic contaminants, and their bioaccumu lation pattern may be masked by seasonal variations in fish lipid content. (C) 2001 by John Wiley & Sons, Inc.