The carbon budget in the northern Adriatic Sea, a winter case study

This presentation describes the activities promoted, and the results obtained, in the framework of the VECTOR project in 2008 for the definition of a winter Carbon budget in the northern Adriatic Sea. The procedure involved the merging of direct measurements during two multidisciplinary cruises and literature data, with the adoption of a box model approach to integrate estimates of stocks and fluxes of carbon species over the total area. Results evidenced that the oligotrophy at the basin scale and the start of primary productivity were present well before the onset of spring stratification, as, in winter, the system underwent a complete reset and the mixing of water masses erased any signal of previous hypoxia or anoxia episodes. The northern Adriatic Sea was phosphorus depleted with respect to C and N availability. This fact confirms the importance of mixing with deep-sea water for P supply to biological processes on the whole. Despite the abundant prokaryotic biomass, the microbial food web was less efficient in organic C production than phytoplankton. In the upper layer, the carbon produced by primary production exceeded the fraction respired by planktonic community smaller than 200 ?m. On the contrary, respiration processes prevailed in the water column below the pycnocline. The carbon budget also proved that the northern Adriatic Sea can be an effective sink for atmospheric CO2 throughout the entire winter season.