Ethanol preservation effects on stable carbon, nitrogen and hydrogen isotopes in the freshwater pearl mussel

Abstract

Chemical preservatives can alter stable isotope ratios in animal tissues. The effects of preservation on δ13C and δ15N values have been investigated in a variety of species, but not on δ2H values or on the freshwater pearl mussel (FPM, Margaritifera margaritifera) tissues. We evaluated the effect of ethanol preservation (unpreserved vs preserved tissues) over 6 months on the δ13C, δ15N and δ2H values of FPM foot and gonad tissues. Ethanol preservation significantly increased δ13C values (foot 0.4 ‰; gonad 0.3 ‰), whereas it did not significantly affect δ15N values (foot 0.2 ‰; gonad − 0.1 ‰). The positive effect of ethanol preservation on δ2H values (foot 7.1 ‰; gonad 14.5 ‰) and the negative effect on C:N ratios (foot − 0.1; gonad − 0.5) depended on the tissue type, with larger effects found on the lipid-rich gonad. Overall, ethanol preservation affected δ2H values more than the δ13C, δ15N or C:N ratios of FPM tissues. After 1 month of preservation, the isotope values remained rather stable, and significant changes were only observed in δ15N values. The results imply that ethanol-preserved FPM samples can be used if potential shifts in isotopic and elemental ratios are accounted for prior running mixing models for estimating dietary proportions.