Lipid biomarkers and trophic linkages between ctenophores and copepods in Svalbard waters

The lipid class compositions of the ctenophores Mertensia ovum and Beroe cucumis were very similar, with polar lipid and wax esters each accounting for 35 to 40% of the total. The fatty acid compositions of the polar lipids in the 2 species were essentially the same, with 22:6n3 and 20:5n3 in a ratio of 2:1 accounting for more than 40% of the total. The fatty acid and fatty alcohol compositions of the wax esters of both species were also essentially the same, with 20:1n9 and 22:1n11 fatty alcohols present in equal amounts accounting for 60% of the total fatty alcohol composition. The fatty acid and fatty alcohol compositions of the wax esters of M, ovum and B, cucumis were averaged and compared, using principal component analyses, to averages derived from published data for the potential prey species: Calanus finmarchicus, C. glacialis, C. hyperboreus, Pseudocalanus acuspes, Acartia longiremis and Metridia longa, The results were consistent with Calanus spp., especially C. glacialis, being the major prey of M. ovum and with M. ovum being the major prey of B. cucumis.