Evidence for dietary time series in layers of cetacean skin using stable carbon and nitrogen isotope ratios.

ABSTRACT: RATIONALE:Stable isotope analysis integrates diet information over a time period specific to the type of tissue sampled. For metabolically active skin of free-ranging cetaceans, cells are generated at the basal layer of the skin and migrate outward until they eventually slough off, suggesting potential for a dietary time series. METHODS:Skin samples from cetaceans were analyzed using continuous-flow elemental analyzer isotope ratio mass spectrometry. We used ANOVAs to compare the variability of ?13 C and ?15 N values within and among layers and columns ("cores") of the skin of a fin, humpback, and sperm whale. We then used mixed-effects models to analyze isotopic variability among layers of 28 sperm whale skin samples, over the course of a season and among years. RESULTS:We found layer to be a significant predictor of ?13 C values in the sperm whale's skin, and ?15 N values in the humpback whale's skin. There was no evidence for significant differences in ?15 N or ?13 C values among cores for any species. Mixed-effects models selected layer and day of the year as significant predictors of ?13 C and ?15 N values in sperm whale skin across individuals sampled during the summer months in the Gulf of Alaska. CONCLUSIONS:These results suggest that skin samples from cetaceans may be subsampled to reflect diet during a narrower time period; specifically different layers of skin may contain a dietary time series. This underscores the importance of selecting an appropriate portion of skin to analyze based on the species and objectives of the study.

SUBMITTER: Wild LA 

PROVIDER: S-EPMC6097889 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature