Dear Colleagues, my co-authors and I are pleased to announce the publication of a new manuscript in the journal Rapid Communications in Mass Spectrometry: Groß, J., Fry, B., Burford, M.A., Bengtson Nash, S. (2021). Assessing the effects of lipid extraction and lipid correction on stable isotope values (δ13C and δ15N) of blubber and skin from southern hemisphere humpback whales. Rapid Communications in Mass Spectrometry 35: e9140 https://doi.org/10.1002/rcm.9140 Abstract RATIONALE The coupled analysis of δ13C and δ15N stable isotope values of blubber and skin biopsy samples is widely used to study the diet of free-ranging cetaceans. Differences in the lipid content of these tissues can affect isotopic variability because lipids are depleted in 13C, reducing the bulk tissue 13C/12C. This variability in carbon isotope values can either be accounted for by chemically extracting lipids from the tissue, or by using mathematical lipid normalisation models. METHODS This study examines: (1) the effects of chemical lipid extraction on δ13C and δ15N values in blubber and skin of southern hemisphere humpback whales, (2) whether chemical lipid extraction is more favourable than mathematical lipid correction and (3) which of the two tissues is more appropriate for dietary studies. Strategic comparisons were made between chemical lipid extraction and mathematical lipid correction, and between blubber and skin tissue δ13C and δ15N values, as well as C:N ratios. Six existing mathematical normalisation models were tested for their efficacy in estimating lipid-free δ13C for skin. RESULTS Both δ13C and δ15N values of lipid-extracted skin (δ13C: -25.57 ‰, δ15N: 6.83 ‰) were significantly higher than bulk skin (δ13C: -26.97 ‰, δ15N: 6.15 ‰). Five of the six tested lipid normalisation models had small error terms for predicting lipid-free δ13C values. The average C:N ratio of lipid-extracted skin was within the lipid-free range reported in other studies while the average C:N ratio of blubber was higher than previously reported. CONCLUSIONS These results highlight the need to account for lipids when analysing δ13C and δ15N values from the same sample. For optimised dietary assessments using parallel isotope analysis from a single sample, we recommend the use of unextracted skin tissue. d15N values should be obtained from unextracted skin, whilst δ13C values may be adequately lipid corrected by a mathematical correction. The publication can be accessed via this link<https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/rcm.9140> or feel free to email<mailto:jasmin.gross@griffithuni.edu.au> me for a copy. Kind regards, Jasmin — — Jasmin Groß (she/her) I PhD Candidate Southern Ocean Persistent Organic Pollutants Program (SOPOPP) Centre for Planetary Health and Food Security | School of Environment and Science | Griffith University | Nathan Campus, 170 Kessels Road, Nathan QLD 4111 Australia HDR Representative on the Griffith Board of Graduate Research I GUPSA Research Officer I ANZSCSMM Chapter Head I Young Science Ambassador Email: <mailto:jasmin.gross@griffithuni.edu.au> jasmin.gross@griffithuni.edu.au<mailto:jasmin.gross@griffithuni.edu.au> Phone: +61 (0)7 3735 9237 Mobile: +61 (0)491 074 464 Twitter: @jasmin4689<https://twitter.com/jasmin4689> <https://www.griffith.edu.au/griffith-sciences/southern-ocean-persistent-organic-pollutants-program>[cid:FB55EE31-E78C-402C-AF1A-CEEAF9511E5E]
