Résumé : This research attempts to determine the role - CO2 source or sink - of the Southern Ocean on a regional and seasonal scale by implementing an integrated multidisciplinary approach which combines in situ measurements, studies of process in laboratory controlled conditions and numerical computation. It approaches the whole of the processes which govern the cycle ... of carbon in the Southern Ocean, from exchanges of CO2 at the air/sea interface until to accumulation of carbon in the sediments. It is based on a mechanistic scientific approach which aims at improving comprehension of the production process and of mineralisation of carbonated biomass in surface water as well as export towards the deep ocean. In particular, the roles of light and the availability in nutrients (major and minor) in the determination of the dominant phytoplanktonic community, and thus of the dynamics of the associated food chain and the carbon exportation, will be studied in areas dominated by various phytoplanktonic communities, namely the diatoms, the colonies of Phaeocystis and the nanophytoplankton. The role of aggregates as carbon conveyors, from surface to the deep water and the sediments, will be investigated with special attention to the following processes : the bacterial mineralisation of aggregates and the production and fate of the barite proxy. The use of the barite as tracer of the exported carbon flux will be evaluated in order to improve the existing transfer functions. Acquired knowledge will then be integrated in a 1D physical and biogeochemical model able to simulate the cycle of carbon as well associated biogenic elements (N, Si, Fe, Mn, Ba) in the whole water column of the Southern Ocean over a seasonal cycle. All together, this study will contribute to establish a diagnostic and predictive model which will be used to evaluate the role of the Southern Ocean in a global perspective.