Short- and Long-Term Effects of Fixation and Preservation on Stable Isotope Values (δ13C, δ15N, δ34S) of Fluid-Preserved Museum Specimens

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Abstract
Concerns about the effects of formalin fixation have largely precluded the use of fluid-preserved museum specimens in stable isotope studies. We sought to determine the magnitude, direction, and causes of formalin-induced change in isotopic values of carbon, nitrogen, and sulfur by examining differences in isotopic signatures between paired fresh-frozen fish tissue samples and tissues subjected to fixation and preservation procedures employed in natural history museums. Several factors were investigated as predictors of formalin-induced change: (1) duration of formalin fixation and ethanol preservation; (2) lipid extraction by formalin and ethanol; and (3) differences in isotopic content among formalin preparations from different manufacturers. Formalin fixation caused a decrease in the δ13C-values across samples and treatments (mean decrease in preserved tissues of 1.1‰ for all treatments, SD = 0.8). The magnitude of depletion depended on the isotopic composition of formalin used for fixation, b...

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