Lipid, sterols and fatty acids of abyssal polychaetes, crustaceans, and a cnidarian from the northeast Pacific Ocean: food web implications

The lipid, sterol, and fatty acid compositions of the abyssal anemone Bathyphellia australis, the 3 polychaetes Laetmonice sp., Paradiopatra sp. and Travisia sp., 3 crustaceans (Munidopsis sp. and 2 lysianassid amphipods), and an unidentified caridean shrimp were determined from a site in the northeast Pacific Ocean. Lipid composition was dominated by phospholipids in most species. However, energy storage lipids (triacylglycerols and wax esters) contributed > 50% to the total lipids in the lysianassid amphipods and the unidentified caridean shrimp, and lipids made up 1.9 and 45 % of amphipod and 14 % of shrimp dry mass, suggesting sporadic feeding and the need for energy storage. The dominant sterol was cholesterol. The presence of phytosterols in the anemone, the polychaetes and Munidopsis sp. suggested consumption of phytodetritus, but none of the specimens had levels suggesting that phytodetritus was their main food resource. The levels of essential photosynthetically derived polyunsaturated fatty acids (PUFA) corroborated the sterol results. The ratio of 18:1 omega 9/18:1 omega 7 further suggested carnivory as the predominant mode of foraging in the abyssal animals, although to varying degrees. Some distinct differences in the fatty acid (FA) composition of these animals allowed for their separation, confirming that FA profiles will be useful in future biomarker approaches to deep-sea food web studies.