Overlooked contribution of the biological pump to the Pacific Arctic nitrogen deficit

Newswise — This study is led by Dr. Chen Jianfang and Dr. Li Hongliang from the Second Institute of Oceanography, Ministry of Natural Resources. Based on the field observation though two Chinese National Arctic Research Expedition (CHINARE) cruises in 2003 and 2008, the team focused the N/P uptake ratio by phytoplankton, seasonal consumption of nutrients, and export of particulate nitrogen in the Chukchi shelf and slope. Accordingly, they highlighted the overlooked contribution of the biological pump to the Pacific Arctic nitrogen deficit.

The role of nitrogen availability in the Pacific Arctic is a subject of much interest and speculation, which is believed to be regulated by the sedimentary denitrification in the Bering Strait-Chukchi Sea. This study demonstrated that the nitrate concentrations of the Pacific inflow gradually decrease northward in association with notable biological utilization. The phytoplankton N/P uptake ratio was higher than the N/P ratio of Pacific inflow water. This uptake ratio, in combination with efficient vertical nitrogen export, serves to preferentially remove nitrogen (relative to phosphorus) from upper waters, thereby further intensifying the Arctic nitrogen deficit (Figure 1).

Accordingly, as large as about 111.7×109 mol N yrof nitrate was extra consumed, according to the real N/P uptake ratio rather than the ratio of the Pacific inflow, which may be as great as half the nitrogen loss ascribed to sedimentary denitrification (Figure 2). This ....

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