Lipid in an arctic food chain: Calanus, Bolinopsis, Beroe

The zooplankton of the fjords of Svalbard in late summer is dominated by copepodites of Calanus glacialis (JASCHNOV). These are consumed by, among others, the lobate ctenophore Bolinopsis infundibulum (O.F. MÜLLER), which is in turn preyed upon by the larger ctenophore Beroe cucumis (FABRICIUS). This simple food chain enables the fate of different lipid classes or fatty acids to be followed from prey to predator. Calanus glacialis, Bolinopsis infundibulum, and Beroe cucumis were sampled from Raudfjorden, Svalbard (79°50′ N, 12°10′ E) in August 1984 and their lipid composition analysed in detail. All three species were rich in lipid and between 50 and 75 % of this lipid was wax ester. The fatty acid composition of this wax ester was different in the three species, with very little similarity in composition between predator and prey in either Calanus/Bolinopsis or Bolinopsis/Beroe. Phospholipid fatty acid composition was also species-specific. Triacylglycerol formed only 2 to 8 % of the total lipid but the fatty acid composition of this triacylglycerol was almost identical in all three species. It is concluded that in the absence of supportive biological information, simple statistical analyses of fatty acid spectra are of limited value in establishing trophic relationship in pelagic marine food webs, although specific individual lipid components may be useful in certain contexts.