Lipid extraction effects on stable isotope values (δ13C and δ15N) of elasmobranch muscle tissue

• Published in: Journal of experimental marine biology and ecology 2012-12, Vol.434-435, p.7-15
• Main Authors: Hussey, Nigel E., Olin, Jill A., Kinney, Michael J., McMeans, Bailey C., Fisk, Aaron T.
• Format: Article
• Language: English
• Subjects: Brackish; Cetacea; Elasmobranchii; Intra- and inter-species variability; Lipids; Marine; Rhincodon typus; Sharks; Skate; Somniosus microcephalus; Stable isotopes; Urea
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/j.jembe.2012.07.012

Given the known effect of lipid content on δ13C values and the potential effect of urea on δ15N values, examining the effects of lipid extraction, which can potentially extract both, is of particular importance for elasmobranch isotope ecology. Through analysing paired δ13C, total %C, δ15N, total %N and C:N values of non-lipid extracted (BULK) and lipid extracted (LE) muscle samples from twenty-one elasmobranch species, we assessed whether lipid extraction was required: (i) to remove lipids given reported low lipid content and, (ii) to determine if δ15N values were affected and whether this relates to the retention of isotopically light urea by elasmobranchs. The mean (±SD) δ13C values of eight out of twenty-one species significantly increased following lipid extraction with two species, the Greenland (Somniosus microcephalus) and whale (Rhincodon typus) shark, showing a marked increase (5.0±0.4‰ and 3.3‰, respectively). The mean (±SD) and maximum increase in δ13C values were 0.6±1.2‰ and 5.9‰, respectively. For δ15N data, thirteen species showed a significant increase following lipid extraction and a concomitant reduction in total percent nitrogen (%N). The C:N ratio for these species also increased from unexpectedly low values of