Particle fluxes over a Mediterranean seagrass bed:a one year case study

Abstract

A sediment trap expenment was carried out in the Bay of Calvi (Corsica, France) over a Posidonja oceanica seagrass bed, at a depth of 36 m. The traps collected 44 samples over a complete annual cycle and allowed a rough partition between 'sinking' and 'resuspended' matter. The measured annual flux of particulate matter amounted to 1.3 kg m-2, of which about 70% arose from sediment resuspension, this process being particularly enhanced d u r ~n g northerly gales. Resuspended material consisted mainly of seagrass-derived detritus, as evidenced by SEM photomicrographs. Chemical analyses of trapped mater~al showed seasonal variations in Inorganic carbon content, organic C/N ratio and 6I3C. Benthic signature (C,,,,,-, C,,,-and 13C-enriched Posidonia-derived matter) was emphasized when resuspension occurred, while planktonic features (N-and 12C-enriched matter) prevailed during bloom conditions.