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

Chemical preservatives can alter stable isotope ratios in animal tissues. The effects of preservation on δ 13 C and δ 15 N values have been investigated in a variety of species, but not on δ 2 H 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 δ 13 C, δ 15 N and δ 2 H values of FPM foot and gonad tissues. Ethanol preservation significantly increased δ 13 C values (foot 0.4 ‰; gonad 0.3 ‰), whereas it did not significantly affect δ 15 N values (foot 0.2 ‰; gonad − 0.1 ‰). The positive effect of ethanol preservation on δ 2 H 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 δ 2 H values more than the δ 13 C, δ 15 N 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 δ 15 N 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.