Effects of chemical preservation on bulk and amino acid isotope ratios of zooplankton, fish, and squid tissues

Abstract

The effects of preservation on bulk δ¹³ C values were variable, where the direction and magnitude of change varied among taxa. The changes in bulk δ¹⁵ N values associated with chemical preservation were mostly minimal, suggesting that storage in formaldehyde or ethanol will not affect the interpretation of δ¹⁵ N values used in ecological studies. The preservation effects on amino acid δ¹⁵ N values were also mostly minimal, mirroring bulk δ¹⁵ N trends, which is promising for future CSIA-AA studies of archived specimens. However, there were substantial differences in phenylalanine and valine δ¹⁵ N values, which we speculate resulted from interference in the chromatographic resolution of unknown compounds rather than alteration of tissue isotopic composition due to chemical preservation.