VERTICAL-DISTRIBUTION AND TEMPORAL VARIATION OF DISSOLVED ORGANIC-CARBON IN THE NORTH-WESTERN MEDITERRANEAN-SEA

During 1991 and 1992, detailed vertical profiles of dissolved organic carbon (DOC) content were obtained monthly, in the North-Western Medit erranean at the DYFAMED-1 site (43 degrees 25'N, 07 degrees 52'E). DOC was measured using a high temperature catalytic oxidation method. In the 150-2000 m layer, DOC distribution was quite uniform, with a conte nt of about 0.6-0.7 mg C l(-1). In surface waters, DOC concentration c hanged according to hydrological situation and primary production cycl e. During February, waters were DOC-homogeneous through the whole wate r column; then surface concentrations increased until autumn with maxi ma of about 1.1-1.2 mg C l(-1) between 0 and 50 m depths. Assuming tha t the DOC is continuously removed from surface waters by diffusive pro cesses during the stratified period and that the DOC accumulated in su rface waters until the end of autumn is removed by advection during th e short period of winter deep water formation, we find that an amount of 18.4 g C m(-2) y(-1) is transferred to the deep layer. This value i s more than twice the particulate organic carbon flux measured on sedi ment traps (4-7 g C m(-2) y(-1)), but agrees with published new produc tion values.