Publication Abstract

Effect of chemical lipid extraction and arithmetic lipid correction on stable isotope ratios of fish tissues

Effect of chemical lipid extraction and arithmetic lipid correction on stable isotope ratios of fish tissues

C.J. Sweeting, N.V.C Polunin and S. Jennings

For accurate interpretation of fish trophodynamics from carbon stable isotope data it is necessary to extract tissue lipids. This is because lipid content varies within and among tissues in both space and time, and because lipids are ¹³C depleted relative to proteins. However, lipid extraction may affect δ¹⁵N, thus requiring costly and time consuming separation of δ¹³C and δ¹⁵N analyses. These problems have prompted the development of arithmetic correction techniques for δ¹³C, but the techniques and their underlying assumptions have not been systematically tested. This study compared the effects of lipid extraction and arithmetic correction techniques on δ¹³C and δ¹⁵N of European sea bass (Dicentrarchus labrax) tissues. Following Folch lipid extraction from muscle and liver, there was a mean increase in δ¹⁵N of 0.77‰, but enrichment varied with lipid content such that effects on δ¹⁵N were hard to predict. Changes in δ¹³C and C:N between untreated and lipid extracted samples reflected the quantity of lipid removed. The arithmetic correction techniques of mass balance and lipid correction were sensitive to the C:N of the lipid extracted tissue and to the assumed depletion of lipid δ¹³C relative to protein δ¹³C. However, the mass balance approach was appropriate for the mathematical correction of bulk tissue data in most circumstances, provided that the C:N of lipid extracted tissue could be determined for a small proportion of samples. Application of mass balance arithmetic correction can lead to significant time and cost savings in trophodynamic studies, because the majority of δ¹³C and δ¹⁵N analyses would not need to be run separately  

Reference:

C.J. Sweeting, N.V.C Polunin and S. Jennings (2006) Effect of chemical lipid extraction and arithmetic lipid correction on stable isotope ratios of fish tissues. Rapid Communications in Mass Spectrometry, 20: 595-601 

C.J. Sweeting, N.V.C Polunin and S. Jennings*

Rapid Communications in Mass Spectrometry, 20: 595-601