THE ROLE OF MESOSCALE FEATURES ON THE DISTRIBUTION OF DCM IN THE SARDINIAN SEA

The Sardinian Sea is located in the Algerian-Provençal basin, an area characterised by intense mesoscale activity. This is one of the less studied region of the Western Mediterranean Sea and the mesoscale variability is far from being adequately known. Five oceanographic cruises were conducted in the Sardinian Sea and the Sardinian Channel from May 2000 to November 2002, mainly to evaluate the impact of the mesoscale phenomena on the marine ecosystem. During these cruises some physical and chemical parameters (CTD, DOC, nutrient, Chlorophyll-a) were measured. In addition a pump and probe fluorometer coupled with a single dimensional model, based on light, biomass and photosynthetic efficiency has been used to evaluate the primary production. The preliminary results confirm the surface layer of the Sardinian sea is dominated by mesoscala phenomena. The SST images, the surface temperature and salinity maps show large anticyclonic eddies (greater than 45 nm). These eddies, that could be originated by the instability of the Algerian Current, reach the Sardinian sea and strongly interact with the MAW circulation in this area. The anticyclonic eddies play an important role in Chlorophyll-a distribution. The North-South sections reveal an undulation of the DCM that seems relate to the position of these eddies in surface layer. Fluorescence highest values generally occur at the rim of the anticyclonic eddies in the slope water. Lowest values are generally detected in the centre of these structures. Finally we also tested new multiparametric instrumentation, which we are going to install in an undulating body, to better analyse the influence of the mesoscala feature on the ecological processes in the surface layer. Further, in order to evaluate the role of the hydrology on the distributions of the ecological processes in the Sardinian Sea, detailed statistical analysis are going on.