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 adjacent epilithic algal dominated community. Isotopic data for consumers are not significantly different in the two communities. Particulate matter and algal material (seagrass epiflora and dominant epilithic macroalgae) appear to be the main food sources in both communities. Generally, the 13C of animals suggests that the seagrass Posidonia oceanica (L.) Delile represents only a minor component of their diet or of the diet of their prey, but the occurrence of a mixed diet is not excluded. P.oceanica dominates the diet of only of few species, among which holothurians appear as key components in the cycling of seagrass material.