Opportunistic feeding on various organic food sources by the cold-water coral Lophelia pertusa

The ability of the cold-water coral Lophelia pertusa to exploit different food sources was investigated under standardized conditions in a flume. The tested food sources, dissolved organic matter (DOM, added as dissolved free amino acids), bacteria, algae, and zooplankton (Artemia) were deliberately enriched in C-13 and N-15. The incorporation of C-13 and N-15 was traced into bulk tissue, fatty acids, hydrolysable amino acids, and the skeleton (C-13 only) of L. pertusa. Incorporation rates of carbon (ranging from 0.8-2.4 mu g C g(-1) DW d(-1)) and nitrogen (0.2-0.8 mu g N g(-1) DW d(-1)) into coral tissue did not differ significantly among food sources indicating an opportunistic feeding strategy. Although total food assimilation was comparable among sources, subsequent food processing was dependent on the type of food source ingested and recovery of assimilated C in tissue compounds ranged from 17% (algae) to 35% (Artemia). De novo synthesis of individual fatty acids by L. pertusa occurred in all treatments as indicated by the C-13 enrichment of individual phospholipid-derived fatty acids (PLFAs) in the coral that were absent in the added food sources. This indicates that the coral might be less dependent on its diet as a source of specific fatty acids than expected, with direct consequences for the interpretation of in situ observations on coral nutrition based on lipid profiles.