Vertical distribution of chlorophyll a along 45゜E in the Southern Ocean, 1981

Surface and vertical observations of chlorophyll α were carried out from the fast ice region to the north of the Subtropical Convergence (STC) on board the icebreaker FUJI in February and March 1981. Sampling stations were arranged along the 45°E meridian including nine vertical observation stations from 67°36\u27S (in polynya) to 43°18\u27S (in the subantarctic water) and nine other vertical observation stations located in a grid pattern in the area of 35°-45°E, 60°-65°S. At the latter vertical observation stations, the pattern of chlorophyll α distribution showed little latitudinal variation but large longitudinal variations. Subsurface chlorophyll α maximum was seen at 75-85m deep at 65°E stations, at about 105m deep at 62°30\u27S stations and was not clear at two 60°S stations. These maxima seemed to coincide with the temperature minimum layer. This is presumed to be related to the circumpolar structure of the antarctic waters as seen from vertical profiles of temperature and salinity. Chlorophyll α standing stock along the 45°E meridian was large (44mg/m^2,integrated from the surface to a depth of 200m) in the water column under fast ice, but small (13mg/m^2) in the pack ice water. The maximum integrated chlorophyll α (75mg/m^2) was obtained at a 62°30\u27S station in the antarctic water. This value is about twice as much as those observed at two stations in the subantarctic water. The data from the pack ice and the fast ice area showed large variations and they suggest high standing stock of phytoplankton in some part of the ice-associated area