Relative impact of a seagrass bed and its adjacent epilithic algal community in consumer diets

The aim of this work was to identify and compare, using nitrogen and carbon stable isotope data, the food sources supporting consumer communities in a Mediterranean seagrass bed (Gulf of Calvi, Corsica) with those in an adjac ent epilithic alga-dominated community. Isotopic data for consumers are not significantly different in the two communities. Particulate matter and alg al material (seagrass epiflora and dominant epilithic macroalgae) appear to be the main food sources in both communities. Generally, the delta(13)C of animals suggests that the seagrass Posidonia oceanica (L.) Delile represen ts only a minor component of their diet or of the diet of their prey, but t he occurrence of a mixed diet is not excluded. P. oceanica dominates the di et of only of few species, among which holothurians appear as key component s in the cycling of seagrass material.