Effects of preservation method on stable carbon and nitrogen isotope values

Some methods of tissue preservation have significant effects on values of stable isotopes of carbon (delta C-13) and nitrogen (delta N-15), but studies on this topic are scattered in the literature. The goals of this study were to (1) summarize the results from studies of preservation effects in the literature and (2) test the effects of four common preservatives on delta C-13 and delta N-15 in epidermis tissue of three turtle species. Turtle tissue samples were subjected to up to five time intervals in five methods of preservation: drying at 60 degrees C for 24 h ( the control), immersion in a 70% ethanol solution, immersion in a saturated NaCl aqueous solution, freezing at -10 degrees C in a frost-free freezer, and immersion in a dimethyl sulfoxide (DMSO)-ethylenediamine-tetraacetic acid buffer. The delta C-13 and delta N-15 values for tissues preserved in 70% ethanol and NaCl aqueous solution were not significantly different from those of tissues dried at 60 degrees C, but samples preserved in DMSO were significantly different from dried samples. Freezing preservation had a significant effect on delta C-13 and delta N-15 at 60 d, which may have resulted from the use of a frost-free freezer. The effects of 20 different preservative methods on delta C-13 and delta N-15 in different tissues are summarized.