Is the southeastern Adriatic Sea coastal strip an eutrophic area?

Abstract

This study intends to understand and assess the effects of the discharge from the Buna/Bojana river delta watersheds on the eutrophic status of the southeastern Adriatic Sea, and contrast this area with the northwestern Adriatic region where the Po River dominates the freshwater discharge into the coastal ocean. We compare observations of inorganic nutrients, turbidity, and physical variables from the two regions and use numerical model results to characterize the physical circulation of the two areas. The area affected by the Po River discharge extends at least one hundred kilometers southward from the delta and approximately 20 km offshore. Maximum chlorophyll concentrations typically occur within the river plume. Similarly, in the southeastern Adriatic Sea, the Buna/Bojana River discharge extends northward along the coasts for approximately one hundred kilometers and contains a large maxima in the regional chlorophyll distribution. The two coastal areas tend to have opposing physical forcing processes: the Po River tends to be affected area by northerly to northeasterly winds that cause downwelling, whereas the Buna/Bojana River on the opposite side of the basin is typically characterized by northerly, upwelling favorable winds. However, during the study period, upwelling is not a dominant feature of the circulation and both the shelf slope current (SouthEastern Adriatic e SEAd current) and the along shore currents in the southeastern Adriatic Sea are northward. The along shore current probably dominated by the river runoff is here described for the first time and called the southeastern Shelf Coastal (SESC) current. Under these conditions, primary productivity is high in both regions leading us to conclude that river plume dynamics and the associated nutrient inputs determine the eutrophication status of the coastal strip, regardless of the circulation regime in the southeastern Adriatic Sea area. The Adriatic southeastern coastal area is an eutrophic area that is strongly affected by freshwater inputs particularly from the Buna/ Bojana River system.