Dear MARMAM subscribers,
My colleagues and I are pleased to announce the publication of our research article: Tatsch, A. C. C., Secchi, E. R., & Botta, S. (2016). Effects of acidification, lipid removal and mathematical normalization on carbon and nitrogen stable isotope compositions in beaked whale (Ziphiidae) bone. *Rapid Communications in Mass Spectrometry, 30*, 460–466. http://doi.org/10.1002/rcm.7457 *ABSTRACT* 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 (δ13C values) can be altered by the presence of 12C-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 (δ15N 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. δ13C and δ15N 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 δ13C values from untreated δ13C values was tested. RESULTS: Significant increases in δ13C values were observed after lipid extraction. No significant changes in δ13C values were found in acidified samples. An interaction between both treatments was demonstrated for δ13C but not for δ15N values. No change was observed in δ15N values for lipid-extracted and/or acidified samples. Although all tested models presented good predictive power to estimate lipid-free δ13C values, linear models performed best. CONCLUSIONS: Given the observed changes in δ13C 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. The article is available from the publisher's website ( http://doi.org/10.1002/rcm.7457) or by request at carol.c.tat...@gmail.com Best regards, Ana Carolina Tatsch MSc. Ana Carolina Corrêa Tatsch Programa de Pós-graduação em Oceanografia Biológica - PPGOB Laboratório de Ecologia e Conservação da Megafauna Marinha- EcoMega Instituto de Oceanografia - IO Universidade Federal do Rio Grande - FURG Rio Grande/RS - Brasil
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