Nutrient matters in the Indian sector of the Antarctic Ocean

Abstract

During the cruise of the R. V. KAIYO MARU (Fisheries Agency of Japan) in the Indian Sector of the Antarctic Ocean from December 1979 to March 1980,the surface observation between Australia and Antarctica and serial observation in the area bounded by 100°-120°E and 61°-65°S off the Budd Coast of Wilkes Land were carried out on board, in order to determine contents of dissolved oxygen, phosphate-phosphorus, silicate-silicon, nitrite-nitrogen and nitrate-nitrogen. Surface observation revealed marked longitudinal changes of nutrient matters related to the existence of the Subtropical Convergence and the Antarctic Convergence. Serial observation showed that distributions of nitrate and phosphate were quite homogeneous below the depth of 100-150m. Relatively low dissolved oxygen content and high silicate content were found up to 100m in the region of about 63°-64°S. This phenomenon may be attributed to the upwelling of water in the region of the Antarctic Divergence. The ratio of nitrate to phosphate in the sea off the Budd Coast was 15.2±0.6 : 1. This ratio was relatively higher than those in other oceans.