Distribution of dissolved organic carbon in and near the Prydz Bay, Antarctica

During the 16th Chinese National Antarctic Research Expedition (CHINARE) (from November 1999 to April 2000) seawater samples were collected for (DOC) determination in the Prydz Bay and its nearby sea areas. DOC concentrations were determined by high temperature catalytic oxidation (HTCO) method. The results shows that DOC concentrations in the upper water column (0～100 m) range from 14.3 to 181.1 μmol/dm3, with averaging 52.5 μ mol/dm3 ( n = 55). These values are slightly higher than those reported for the Ross Sea, the Pacific Ocean and others. Profiles of DOC concentration in the study areas show a decreasing concentration with increasing depth in the upper 100 m,which is related to biological activities in the water column. DOC concentrations below 100 m are relatively constant with a mean of 40.4 μmol/dm3. These DOC are unactive for physical and biological activities and are called refractory DOC. Concentration of the refractory DOC in the study area is consistent with the previous reported values for the Southern Ocean, which is about 41 μmol/dm3. Based on the difference between the measured DOC concentration and the refractory concentration, the excess DOC concentration in the upper column can be calculated at every station. The excess DOC shows a spatial variability with a higher excess in the north of 64°S and little excess in the south of 64°S. In conclusion,DOC concentrations in the Prydz Bay and its nearby sea areas are consistent with the previous reported values in the Southern Ocean, which show a low DOC concentration with respect to the other oceans.Distribution of surface DOC concentrations in the study areas shows an increase from the southwestern to the northeastern, which is ascribed to the northern spread of continental shelf water from the Prydz Bay in summer. Contents of DOC and their distribution in the Prydz Bay and its nearby sea areas are mainly controlled by physical and biological processes.