Quality and quantity of exchanges between lagoon and sea. Organic and inorganic micropollutants

The present study was undertaken to examine the biogeochemical fluxes of dissolved and particulate organic material between the Lagoon of Venice and the Northern Adriatic Sea. The greatest contribution to the organic matter in all samples came from marine sources, with bacterial sources contributing the second greatest amount. Only minor amounts of terrestrial organic biomarkers were present, and sewage biomarkers were observed in only one sample. No significant differences in lipid biomarker distributions or concentrations were observed between the port entrances of Lido and Malamocco or between samples collected in the years 2001 and 2002. During each season, concentrations were higher in the SPM than in the DOM, with marine inputs dominating throughout the year. Most differences could be attributed to differences in source materials, and primarily to inputs from phytoplankton. Dissolved and particulate lipid fluxes were generally greater on the incoming flood tide than during the ebb tide, suggesting a net transport of dissolved lipids from the Adriatic into the Lagoon. Some seasonal variations from this trend did exist, and resulted in net transport from the Lagoon to the Adriatic. Fatty acids showed the highest fluxes of material with hydrocarbon and sterol fluxes being one to two orders of magnitude lower than those for fatty acids.