Nitrate and phosphate profiles in the Banda Sea during the northwest monsoon

Abstract

The Banda Sea (BS) is subjected to monsoonal winds that affected upwelled rich nutrient waters and primary production. However, nutrient characteristic in the region is less constrained. Here, we examine nitrate and phosphate profiles in the Banda Sea from data collected during the northwest monsoon. Waters along the surface density (σθ ) < 22 were dominated by less saline originating from western Indonesia (i. e., Java Sea), accompanied by Indonesian throughflow water Banda (23.0-25.0σθ ) and Banda water (26.5-27.0σθ ), respectively. Surface water was accompanied by low nitrite+nitrate () and phosphate (), meanwhile, the average and concentrations in the upper 500 m were slightly higher in the western part than those in the eastern part suggesting additional sources from upwelled waters. Furthermore, the average nitrite+nitrate to phosphate ratio (N:P ratio) was 11.2:1, indicating nitrogen is a limiting factor for the growth of primary producers, and other sources may play a more dominant role. Two distinct layers in the euphotic zone within different sources and mechanisms namely the nutrient-depleted layer and nutrient-repleted layer were observed. Overall, the result of this study can only be seen as a starting point toward a comprehensive and holistic understanding of the nutrient biogeochemistry of the Indonesia Seas.