Meeting Abstract

P1.94  Monday, Jan. 4  Using GC-FID in Conjunction with GC-MS to Identify Fatty acid Methyl Esters in Sympatric Marine Mammal Species YOUNG, K.E.*; QUINN, S.M; WAITE, J.N.; USENKO, S.; ANDREWS, R.D.; TRUMBLE, S.J.; Baylor University; Baylor University; University of Alaska Fairbanks; Baylor University; University of Alaska Fairbanks; Baylor University stephen_trumble@baylor.edu

Northern fur seal (NFS, Callorhinus ursinus, n = 22) and Steller sea lion (SSL, Eumetopias jubatus, n = 12) blubber samples were collected from adults occupying the same rookery near the Lovushki Island complex, Russia. The objective of this study was to compare similarity of identified fatty acids (FA) using gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS) within and between species. GC-FID identified a minimum of 25 fatty acid methyl esters (FAME) from each blubber sample against a standard set of 40 FAME. Using the Sørensen similarity index (SI) on GC-FID data we determined an 85 percent similarity on FAME between species inhabiting the same rookery. However, GC-MS identified an additional 21 FAME for NFS and 23 FAME for SSL, as well as an additional 10 FAME common to both species. Combining methods resulted in a decreased SI of 60 percent between SSL and NFS inhabiting the same rookery. Relying solely on GC-FID, which is routinely used as a method in fatty acid analysis in marine mammal predator-prey studies, would result in a significant artificial increase in shared FAME recovered from depot lipids. Because FA composition of depot lipids has long been known to reflect diet, this may lead to spurious conclusions relating to predator-prey interactions or resource partitioning between species occupying similar rookeries. While analysis of FAME by GC-FID analysis has proven to be a most reliable and accessible method for routine quantification of FA composition, we propose incorporating GC-MS for as an additional method to indentify unknown FA peaks.