DISPERSAL PROCESSES OF FRESHWATERS IN THE PO RIVER COASTAL AREA1

Tidal effects on the vertical structure and dynamic pattern of the freshwater plume in the PO River coastal area were evaluated. A large vertical density gradient just below the surface and a lateral density front separate the fresh and seawatcrs. The horizontal extent of the river waters was followed by the continuous analysis of nitrate, whose conservative behavior, evidenced by a linear relationship with salinity, is justified by the observed trophic conditions. The Adriatic Sea is a quasi-isolated basin connected with the Mcditerrancan through the Otranto Channel. Several rivers (PO, Adige, Brenta, Piave, Tagliamento, and Isonzo ) flow into the Adriatic along its northwestern coasts, generating a continuous supply of nutrients and freshwater which, mixing with the oligotrophic waters incoming from the Mediterranean, make the productivity of this basin one of the highest of the whole Mediterranean Sea ( Faganclli 1961) . Although measurements have been made from both the chemical (McGill 1966; Franc