FEEDING OF THE SPARID FISH SARPA-SALPA IN A SEAGRASS ECOSYSTEM - DIETAND CARBON FLUX

In Revellata Bay (Gulf of Calvi, Corsica, France), the sparid fish Sar pa salpa L. is the main macro-consumer of Posidonia oceanica (L.) DELI LE leaf. Stomach contents were analysed and C-13/C-12 isotopic ratios were measured in fish muscle and potential food sources (algae, P. oce anica leaf and its epiphytes) to determine their relative contribution to the fish diet. S. salpa has an age-related mixed diet: juveniles a re plankton feeders, young, sub-adults and adults are herbivorous, and , the older the individuals, the higher the relative contribution of P . oceanica to the diet. Our results and former studies of carbon stock s and fluxes in the P. oceanica bed of Revellata Bay have enabled an e stimation of the general impact of S. salpa grazing on infralittoral c ommunities: the studied species consumes 24 g C.m-2.a(-1) from P. ocea nica leaf, 4.8 from epiphytes and 13 from epilithic algae. The fish ne t production and biomass turnover in that zone have been estimated to be 1.2 g C.m(-2).a(-1) and 1.5 a(-1), respectively.