Nitrate source identification and quantification in the euphotic zone of the Baltic Proper using nitrogen and oxygen stable isotopes

将通过氮和氧稳定同位素确定和量化波罗的海本身的硝酸盐来源。波罗的海受到集水区(面积是海洋本身面积的4倍)和那里的人为活动的强烈影响。特别是，通过河流、点源和大气沉积输入的硝酸盐和磷会导致富营养化，从而加剧底层水域的缺氧。另一个来源是蓝藻在真光区的固氮作用。潜在的硝酸盐来源很大程度上是已知的。然而，关于它们的数量和对波罗的海本身真光区初级生产的相对重要性，仍然存在很大的不确定性。反硝化物法能够同时测量硝酸盐的氮和氧同位素，这将是该地区首次应用。同位素特征使区分不同的氮源和影响真光层中硝酸盐浓度的过程成为可能。将分析潜在的来源(硝酸盐池、大气沉降加上第一次溶解的有机氮)。更多的实验研究将有助于确定支持初级生产的不同氮素形态(无机和有机)的相对重要性。将建立波罗的海中部真光层的硝酸盐预算。

Nitrate sources of the Baltic Proper will be identified and quantified by means of nitrogen and oxygen stable isotopes. The Baltic Sea is strongly influenced by the catchment (covering 4 times the area of the sea itself) and the anthropogenic activity there. In particular nitrate and phosphorus inputs via rivers, point sources, and atmospheric deposition cause eutrophication which aggravate anoxia in bottom waters. An additional source is nitrogen fixation by cyanobacteria in the euphotic zone. Potential nitrate sources are largely known. However, there are still substantial uncertainties regarding their quantity and relative importance for the primary production in the euphotic zone of the Baltic Proper. The denitrifier method, which enables measurement of both nitrogen and oxygen isotopes of nitrate, will be applied for the first time in this region. The isotope signature makes it possible to distinguish between different nitrogen sources and processes affecting the nitrate concentration in the euphotic layer. Potential sources (nitrate pool, atmospheric deposition plus for the first time dissolved organic nitrogen) will be analyzed. Additional experimental studies will help to determine the relative importance of different nitrogen forms (inorganic and organic) supporting the primary production. A nitrate budget for the euphotic layer in the central Baltic Sea will be established.