PHYSICAL AND CHEMICAL PROPERTIES OF SURFACE WATER IN THE SOUTHERN OCEAN IN SUMMER 1991/92 (16th Symposium on Polar Biology)

摘要

Surface water temperature and salinity were continuously recorded using the Surface Water Monitoring System in the Australasian sector of the Southern Ocean during the JARE-33 cruise in summer 1991/92. Moreover, concentrations of nitrate-N plus nitrite-N and silicate-Si were determined. Three oceanographic fronts were recognized based on the physical variables: the Subtropical Convergence, which divided the Subtropical Zone and the Subantarctic Zone, the Subantarctic Front, which divided the Subantarctic Zone and the Polar Frontal Zone, and the Antarctic Polar Front, which divided the Polar Frontal Zone and the Antarctic Zone. The positions of the fronts were consistent with previous results. Large meridional gradients of nutrient concentrations were observed in the fronts. The nutrient conditions are summarized as follows. Subtropical Zone: both nutrient concentrations are less than the detectable limits. Subantarctic Zone: nitrate plus nitrite is several μM but silicate is still less than the detectable limit. Polar Frontal Zone: the former reaches ca. 20μM and the latter increases several μM. Antarctic Zone: the former is ca. 20 μM and the latter is also over 20 μM. These different behaviors of two different nutrients seem to be important environmental conditions for geographical distribution of phytoplankton in the Southern Ocean.