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 aus- tralis, 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 19 and 45% of amphipod and 14% of shrimp dry mass, suggesting sporadic feeding and the need for energy stor- age. The dominant sterol was cholesterol. The presence of phytosterols in the anemone, the poly- chaetes 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 photo- synthetically derived polyunsaturated fatty acids (PUFA) corroborated the sterol results. The ratio of 18:1ω9/18:1ω7 further suggested carnivory as the predominant mode of foraging in the abyssal ani- mals, 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 bio- marker approaches to deep-sea food web studies.