LIPIDS IN ARCTIC BENTHOS - DOES THE FATTY-ACID AND ALCOHOL COMPOSITION REFLECT FEEDING AND TROPHIC INTERACTIONS

Arctic benthic organisms of various taxa (Anthozoa, Polychaeta, Pantop oda, Crustacea, Echinodermata) were collected on the shelves off north east Greenland, Spitsbergen and the western Barents Sea. Their fatty a cid compositions were generally characterised by the predominance of t he polyunsaturated fatty acids 20:5(n-3) and 22:6(n-3) together with t he saturated fatty acid 16:0, which reflect the dominance of phospholi pids. The fatty acid compositions of most benthic specimens were influ enced by fatty acids of dietary origin. High amounts of the fatty acid 16:1(n-7), typical of diatoms, were found in different taxa from the northeast Greenland shelf. The 18:4(n-3) fatty acid, often typical of non-diatom input, was only dominant in Ophiopholis aculeata from the S pitsbergen shelf In some taxa small amounts of wax esters were detecte d with alcohol moieties similar to those of the dominant Arctic copepo ds. The occurrence of intact wax esters, as well as the wax ester typi cal fatty acids 20:1(n-9) and 22:1(n-11), also suggested ingestion of large herbivorous copepods. An unusual fatty acid composition was foun d for most brittle stars, due to a ratio of the 18:1(n-9) and (n-7) fa tty acid isomers below 1 with lowest ratios of 0.1. A similar low rati o was also detected in the polychaete Onuphis conchylega. The extremel y low portions of the 18:1(n-9) fatty acid are striking, since carnivo res are generally characterised by high levels of this fatty acid. A c lear gradient from low 18:1(n-9) to (n-7) ratios in suspension feeders , via predatory decapods, to higher ratios in the scavenging amphipods was a major characteristic of the benthic species. Our investigations showed that lipid analyses can give important hints on trophic relati onships of benthic species and may serve as means to establish the int ensity of pelagic-benthic coupling.