Accounting for the effects of lipids in stable isotope (delta C-13 and delta N-15 values) analysis of skin and blubber of balaenopterid whales

作者：Ryan Conor^*; McHugh Brendan; Trueman Clive N; Harrod Chris; Berrow Simon D; O' Connor Ian

来源：Rapid Communications in Mass Spectrometry, 2012, 26(23): 2745-2754.

DOI：10.1002/rcm.6394

RATIONALE Stable isotope values (delta C-13 and delta N-15) of darted skin and blubber biopsies can shed light on habitat use and diet of cetaceans, which are otherwise difficult to study. Non-dietary factors affect isotopic variability, chiefly the depletion of C-13 due to the presence of C-12-rich lipids. The efficacy of post hoc lipid-correction models (normalization) must be tested. %26lt;br%26gt;METHODS For tissues with high natural lipid content (e.g., whale skin and blubber), chemical lipid extraction or normalization is necessary. C:N ratios, delta C-13 values and delta N-15 values were determined for duplicate control and lipid-extracted skin and blubber of fin (Balaenoptera physalus), humpback (Megaptera novaeangliae) and minke whales (B. acutorostrata) by continuous-flow elemental analysis isotope ratio mass spectrometry (CF-EA-IRMS). Six different normalization models were tested to correct delta C-13 values for the presence of lipids. %26lt;br%26gt;RESULTS Following lipid extraction, significant increases in delta C-13 values were observed for both tissues in the three species. Significant increases were also found for delta N-15 values in minke whale skin and fin whale blubber. In fin whale skin, the delta N-15 values decreased, with no change observed in humpback whale skin. Non-linear models generally out-performed linear models and the suitability of models varied by species and tissue, indicating the need for high model specificity, even among these closely related taxa. %26lt;br%26gt;CONCLUSIONS Given the poor predictive power of the models to estimate lipid-free delta C-13 values, and the unpredictable changes in delta N-15 values due to lipid-extraction, we recommend against arithmetical normalization in accounting for lipid effects on delta C-13 values for balaenopterid skin or blubber samples. Rather, we recommend that duplicate analysis of lipid-extracted (delta C-13 values) and non-treated tissues (delta N-15 values) be used.

• 出版日期2012-12-15