Skeletal growth, respiration rate and fatty acid composition in the cold-water coral Lophelia pertusa under varying food conditions

Reefs of the cold-water coral Lophelia pertusa form biodiversity-rich habitats in the deep ocean, but physiology, reproduction, feeding and growth in this species remain poorly investigated. Food supply to reef sites varies considerably both spatially and temporarily. In this study we investigated the effects of starvation and zooplankton feeding on respiration and growth of L. pertusa. In our first experiment, corals were starved for 6 mo, resulting in a 40% decrease in respiration but no visible effects on coral condition or survival. In a second experiment, corals were fed nauplii of Artemia salina for 15 wk at 4 different densities; the organic carbon provided corresponded to between 20 and 300% of the carbon turned over by initial respiration. Respiration rate increased with zooplankton food density, but no effect on skeletal growth could be detected. Skeletal growth remained positive even at low food density. Compared to initial conditions, there was a general decrease in the total concentrations of both structural and storage fatty acids independent of food treatment, but no significant effect among the treatments was discovered. The amount of organic carbon and nitrogen also decreased during the experiment, although significantly less in the highest food density compared to the lowest. The results indicate that L. pertusa is highly tolerant to living on minimal resources for periods of several months. Response-times to varying food conditions were slow, but results suggest that tissue content and composition is a better indicator of food conditions in L. pertusa compared to calcification rates.