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Effects of acidification, lipid removal and mathematical normalization on carbon and nitrogen stable isotope compositions in beaked whale (Ziphiidae) bone
Author(s) -
Tatsch Ana Carolina C.,
Secchi Eduardo R.,
Botta Silvina
Publication year - 2015
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7457
Subject(s) - chemistry , beaked whale , whale , normalization (sociology) , nitrogen , stable isotope ratio , isotopes of carbon , isotope , environmental chemistry , minke whale , δ13c , ecology , organic chemistry , total organic carbon , physics , quantum mechanics , biology , balaenoptera , sociology , anthropology
Rationale The analysis of stable isotopes in tissues such as teeth and bones has been used to study long‐term trophic ecology and habitat use in marine mammals. However, carbon isotope ratios (δ 13 C values) can be altered by the presence of 12 C‐rich lipids and carbonates. Lipid extraction and acidification are common treatments used to remove these compounds. The impact of lipids and carbonates on carbon and nitrogen isotope ratios (δ 15 N values), however, varies among tissues and/or species, requiring taxon‐specific protocols to be developed. Methods The effects of lipid extraction and acidification and their interaction on carbon and nitrogen isotope values were studied for beaked whale (Ziphiidae) bone samples. δ 13 C and δ 15 N values were determined in quadruplicate samples: control, lipid‐extracted, acidified and lipid‐extracted followed by acidification. Samples were analyzed by means of elemental analysis isotope ratio mass spectrometry. Furthermore, the efficiency of five mathematical models developed for estimating lipid‐normalized δ 13 C values from untreated δ 13 C values was tested. Results Significant increases in δ 13 C values were observed after lipid extraction. No significant changes in δ 13 C values were found in acidified samples. An interaction between both treatments was demonstrated for δ 13 C but not for δ 15 N values. No change was observed in δ 15 N values for lipid‐extracted and/or acidified samples. Although all tested models presented good predictive power to estimate lipid‐free δ 13 C values, linear models performed best. Conclusions Given the observed changes in δ 13 C values after lipid extraction, we recommend a priori lipid extraction or a posteriori lipid normalization, through simple linear models, for beaked whale bones. Furthermore, acidification seems to be an unnecessary step before stable isotope analysis, at least for bone samples of ziphiids. Copyright © 2015 John Wiley & Sons, Ltd.