Biochemical composition of the cold-water coral Dendrophyllia cornigera under contrasting productivity regimes: insights from lipid biomarkers and compound-specific isotopes

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anglais. The cold-water coral (CWC) Dendrophyllia cornigera is widely distributed in areas of both high and low productivity, suggesting a significant trophic plasticity of this coral depending on the food available in the environment. In this study, lipid biomarkers and their isotopic signature were compared in colonies of D. cornigeraand sediment from the highly productive Cantabrian Sea (Northeast Atlantic Ocean) and the less productiveMenorca Channel (Western Mediterranean Sea). Lipid content and composition in coral tissue clearly reflectedthe contrasting productivity in the two areas. Cantabrian corals presented higher content in fatty acids (FA),fatty alcohols and sterols than Menorca corals.Energy storage (saturated + mono-unsaturated FA) to structural (poly-unsaturated FA) ratio was higher inCantabrian than in Menorca corals. The high ΣC20:1 content as well as PUFA(n-3)/PUFA(n-6) ratio suggest thatCantabrian corals mainly feed on phytoplankton and herbivorous grazers. This is also supported by the highermono-unsaturated fatty alcohols (MUOH) and long chain mono-unsaturated fatty alcohols (LCMUOH) content inCantabrian compared to Menorca corals. Conversely, higher PUFA(n-6) content in Menorca corals, with thedominance of C22:4(n-6) and C20:4(n-6), as well as the dominance of cholesterol and norC27Δ5,22 among sterols,point to a higher trophic role of dinoflagellates and invertebrates. The observed geographical variability introphic ecology supports a high trophic plasticity of D. cornigera, which may favour the wide distribution of thisCWC in areas with highly contrasted food availability.