Fluxes of Suspended Materials in the North Adriatic Sea (PO Prodelta Area)

Two time-series sediment traps were deployed south-east of the Po River delta (North Adriatic Sea) in 23m of water at 12 meters and 21 meters depths from 12/20/89 to 06/26/90. Temperature, conductivity, salinity, pH, Eh, O₂, transmittance profiles, wave height, speed and direction of currents were measured. Bottom sediments and river suspended matter were periodically collected during the same period. Organic carbon, Al, Fe and Mn concentrations and partitioning of Phosphorous on the solid phase in sediment samples were determined. This made it possible to calculate vertical fluxes at two water levels, and then to quantify and separate veritical fluxes of sinking particles into fluxes of lateral transports (river input), primary production and resuspension. To do so, the approach was based on the identification, comparison and integration of two different label substances (POC and Mn). This led to the finding that sediment fluxes and biogeochemical characters of suspended matter are in good agreement with seasonal differences and short-term events such as river floods, algal blooms and marine storms. A decrease in organic carbon along the water column (5.13% mean value at 12 in, 2.84% mean value at 21 m) with minimal values in the bottom sediment (1.49% mean value) was detected. Resuspension and reoxygenation increase the mineralization of organic matter (occurring already in water column). Differences in adsorption and desorption in the fine particulates of fundamental elements for primary production such as phosphorous were detected at different levels in the water column and in the bottom sediments.