Can we use stable isotopes for ecotoxicological studies? Effect of DDT on isotopic fractionation in Perca fluviatilis

Nitrogen and carbon stable isotope analyses are frequently used to assess contaminant biomagnification in animals in the wild. Previous studies, mainly on plant but also on animal tissues, have shown that chemical stress can lead to shifts in δ15N. In order to assess if an exposure to DDT at realistic concentration disrupted stable isotope signature in animals, δ15N and δ13C were studied in several tissues (liver, muscle, gill) of Perca fluviatilis fed with the same commercial diet uncontaminated or contaminated with DDT. We observed no DDT effect on the δ15N and δ13C of fish tissues. Our results show that stable isotopes can remain useful for field ecotoxicological studies despite food-chain contamination. However, correlations between the δ13C or δ15N values measured in the different organs were only found in DDT treated fish, suggesting some disruption of major biochemical compound metabolism in tissues.