Unravelling the importance of the Laptev Sea system in the Arctic biogeochemical cycling of nitrogen

该项目将对拉普捷夫海水体中的不同氮源进行定量评估。溶解硝酸盐和有机氮的稳定氮和氧同位素将与水化学数据和水的同位素组成一起用于研究无机氮和有机氮流入北冰洋的作用。北极的变暖导致河流径流增加和永久冻土融化，这两者都导致流入北极沿海海洋的氮通量增加。目前还不清楚这些现象是否会影响北极的初级生产力和大气碳的吸收，因为我们对北极氮循环的了解充其量也是有限的。该提案中建议的稳定同位素方法是调查拉普捷夫海氮源和循环的有效和具有成本效益的方法，将是在北冰洋进行的第一次硝酸盐双同位素研究。除了对拉普捷夫海氮源的相对重要性进行可靠的估计外，该项目还旨在通过测量其同位素组成，了解溶解有机氮在北极氮循环中的作用及其在北极大陆架初级生产力中的潜在作用。

This project will provide a quantitative assessment of the different nitrogen sources in the water column of the Laptev Sea. Stable nitrogen and oxygen isotopes of dissolved nitrate and organic nitrogen will be used together with hydro-chemical data and the isotopic composition of the water to study the role of riverine input of inorganic and organic nitrogen in the Arctic Ocean. The warming in the Arctic is causing an increase in river runoff and a thawing of the permafrost, which both lead to an increased flux of nitrogen to the coastal seas of the Arctic. It is still unclear if those phenomena will affect the Arctic primary productivity and uptake of atmospheric carbon because our knowledge of the nitrogen cycle in the Arctic is limited at best. The stable isotope approach suggested in this proposal is an efficient and cost-effective way of investigating nitrogen sources and cycling in the Laptev Sea and will be the first nitrate dual isotopes study performed in the Arctic Ocean. In addition to produce a robust estimation of the relative importance of nitrogen sources in the Laptev Sea, this project aims to understand the role of dissolved organic nitrogen in the Arctic nitrogen cycle and its potential role in the primary productivity on Arctic shelves by measuring its isotopic composition.