Winter preconditioning determines feeding ecology of Euphausia superba in the Antarctic Peninsula

We examined the feeding ecology and lipid composition of Antarctic krill Euphausia superba around the northern Antarctic Peninsula from 2001 to 2012. We used lipid biomarkers to quantify feeding patterns and relate the variability in biomarkers to environmental conditions that structure the phytoplankton community. Fatty acid profiles varied among years, with some years dominated by lipids indicative of herbivory, while other years were indicative of greater omnivory. Principal component analysis of 60 fatty acids showed that 3 principal components (PCs) explained approximately 50% of the variability in fatty acid profiles. The first PC separated the fatty acid indicators along a herbivory-omnivory-carnivory gradient. Correlations between the gradient of herbivory and carnivory, as summarized by the first PC, were found with both winter sea ice extent (r = 0.55, p < 0.01) and with ENSO conditions the previous winter (r = 0.88, p < 0.001). These findings suggest that climatic conditions during the late winter precondition the pelagic ecosystem around the Antarctic Peninsula, impacting the trophic ecology of Antarctic krill the following summer.