A CONTRIBUTION TO THE STUDY OF HYDRODYNAMICS AND BIOGEOCHEMICAL PROCESSES IN SHALLOW WATER ENVIRONMENTS (COASTAL AREAS, LAGOON, LAKES) BY WAY OF ENVIRONMENTAL INDICATORS

An integrated monitoring network aimed to the management of hypoxia environmental and socio-economic impacts was developed for a NW Adriatic coastal zone (Italy). The monitoring network was planned by linking scientific knowledge on hypoxia with in situ experimental investigations. Here, we present some results of the shelf area survey aimed to identify the most suitable location for the buoy devoted to real-time data collection. Sediment lithology, water content, oxidation levels, Eh, pH, total organic carbon (TOC), total nitrogen (TN), C/N and ?13C, 7Be and 137Cs in surface (SUP) and sub-surface (SUB) layers were analysed at 14 sampling sites along 3 land-sea transects. The first aim was to assess the representativeness of the data collected at sampling time compared to the study area average conditions. A distinction between a 'still mobile', non-permanent surface layers (SUP) and an already consolidated, permanent (SUB) ones was therefore adopted. The second aim was to identify the shef areas characterised by the highest vs. lowest variability between the two layers. To achieve this goal sedimentological and biogeochemical differences between SUP and SUB layers were highlighted by way of the elaboration of easy-to-use indicators derived from the analytical data. The obtained results show an inshore area in front of the river mouth characterised by any deposition of fresh, river-derived material take place. The northern sector and the offshore stations are otherwise characterised by a very active sedimentation of riverine material. This pattern suggest that river-derived organic-rich fine sediments are pushed northwestward off the river mouth and expand offshore only 25 km far from it then entering within the Western Adriatic Coastal Current driving the sediment toward SE. A comparison with the sea floor morphology further suggest the presence of a local gyre that determines a clock-wise circulation cell that influence the local sediment transport.