A simplified approach to evaluate sedimentary organic matter fluxes and accumulation on the NW Adriatic Shelf (Italy)

Total organic carbon (TOC) and total nitrogen (TN) concentrations and fluxes were estimated in surface sediments of a shelf area in the NW Adriatic Sea (Italy), together with lithology and Pb-210 contents at 18 stations during four cruises (1996-1998) carried out offshore of the Po River delta. Mass accumulation rates (MAR) were <0.1-0.8 g cm-2 yr-1 and surface concentrations of TOC and TN were within the range of 0.5-1.4 and 0.08-0.19% of dry weight, respectively. Their spatial variability showed a direct correlation with the inputs of suspended matter from the Po River. A simplified approach to calculate average TOC and TN yearly fluxes to surface sediments over the whole area was adopted by subdividing the study area into three zones, selected on the basis of the grain size distributions and of the influence of the Po River discharge, in order to take into account major differences of sedimentological regimes on the shelf. The values of TOC ( 103 tCyr -1) and TN ( 103 tN yr-1) fluxes for these areas were, respectively, 17.9 and 2.4 near the delta, 45.2 and 6.5 for the intermediate area, and 9.5 and 1.5 for the offshore area.