DISTRIBUTION OF THE MAJOR INORGANIC NUTRIENTS IN THE ROSS SEA, ANTARCTICA

Abstract

Despite high concentration of nutrients in ambient water, the Antarctic has low chlorophyll a where primary production is low compared to other regions on an annual basis. Our research region is the Ross Sea, known as one of the most productive polynya. We investigated spatial and temporal variations of nutrients to understand the environmental changes in the Ross Sea. Seawater sampling was carried out at 13 stations in 2018 (ANA08C, February 25 March 1) and 17 stations in 2019 (ANA09B, January 16 21). In 2018, the average concentrations of phosphate, nitrate + nitrite and silicate were 2.11 ±0.14, 20.94 ±1.22, and 74.34 ±13.45 μM, respectively. Overall, no significant difference was shown between 2018 and 2019, average concentrations of phosphate, nitrate + nitrite and silicate in 2019 were 1.97 ±0.22, 28.25 ±3.51, and 72.90 ±12.50 μM, respectively. Dissolved inorganic ammonium concentration remained low ranging from 0 to 1.56 μM (2018) and from 0 to 1.09 μM (2019) throughout the study region and it was just above the level of detection at some stations. We found high concentration of nutrients at the Ross Sea continental shelf. Consistent with our result, warm circumpolar deep water (CDW) intruded on the Ross Sea continental shelf and flowed toward the Ross sea ice shelf. This flow pattern suggests that the major nutrients seemed to be provided with intrusion of CDW.