Stability of fatty acid composition in seal blubber during long-term storage

Abstract

This study was performed to evaluate the stability of the fatty acid (FA) composition of blubber from Baltic grey seals Halichoerus grypus archived at -25C in the Swedish Environmental Specimen Bank (SESB). Possible alterations of FA compositions with storage time and temperature were evaluated. Blubber from 5 seals was kept at + 2C and at -20C and sampled for up to 6 mo and 33 mo, respectively. Furthermore, FA profile stability was evaluated in blubber stored in the SESB for 4 and 6 yr. This was done by re-sampling and re-analyzing blubber samples from SESB. In both parts of the study, a principal component analysis was performed on 48 FAs comprising 98 to 99% of the total FAs in blubber of Baltic grey seals. We found no indication of a critically altered FA composition, neither in blubber stored at + 2C for 6 mo nor in blubber stored at -20C for 33 mo. The re-analysis of samples stored in SESB for ~4 to 6 yr only differed for a few FAs in some samples. The most remarkable differences were a slight increase in some long-chain unsaturated . As an increase in long-chain polyunsaturated FAs due to storage is highly unlikely, we believe that this is probably more due to the sampling technique than to a critically altered FA composition due to storage. Our results suggest that archived seal blubber may be safely used in retrospective analyses of diet using an FA signature analysis technique.