In the framework of the project, historical data series that characterise the marine ecosystem will be analysed in addition to acquisitions and elaborations of data relevant for the explanation of processes related to unusual phenomena in the Adriatic Sea. These phenomena, principally bottom layer anoxia and mucilage, recurred with increasing frequency during the last decade. Methods of elaboration widely applied in marine science will be used. The statistical model of long-term changes in the water column of the northern Adriatic for the period 1966-2000 will be complemented with new data and extended with available data on dissolved organic carbon, surface active matter, primary and secondary production, pico- and nano-plankton, as well as on composition of the microphytoplankton community. The role of geostrophic circulation combined with dynamics of the Po River discharges in the formation of hypoxic water in the bottom layer, as well as in the aggregation and accumulation of mucilaginous aggregates will be investigated. Moreover, the role of the microbial loop and changes in the microphytoplankton species composition in triggering the mucilage phenomenon will be also evaluated. The results obtained in the course of this project will improve ecosystem monitoring from the aspect of a more rational management of the Adriatic area and protection of the sea for sustainable development. The rationale for future research is based on clear needs to define a baseline from which to assess the effects of climatic global changes on the Adriatic ecosystem.