The nitrogen isotopic composition of nitrate and suspended particulate nitrogen (PN) in the upper 500 m water column along a transect in the western Bering Sea was analyzed to characterize the nitrogen cycle in summer. The δ¹⁵N of nitrate (δ¹⁵N–NO₃) increases into the surface, in strong correlation with the upward decrease in nitrate concentration, reflecting the effect of nitrate assimilation by phytoplankton. The isotope effect of nitrate assimilation (¹⁵ε_NO3) in the basin and the slope is estimated to be 6.1 ± 2.1‰ and 4.1 ± 0.8‰, respectively. The variation of ¹⁵ε_NO3 in the basin is probably due to the difference in phytoplankton community, while the ¹⁵ε_NO3 in the slope is underestimated by at least 1‰ by nitrification. There are four types of relationship between δ¹⁵N of PN (δ¹⁵N-PN) and dissolved inorganic nitrogen concentration ([DIN]), i.e., a constant low δ¹⁵N-PN with slightly varying [DIN] in the euphotic zone of the basin, a negative correlation in the euphotic zone of the slope, a positive correlation in the depth from the bottom of the euphotic zone to the temperature minimum layer (T_min layer), and a relatively constant δ¹⁵N-PN at varying [DIN] below the T_min layer. These relationships reflect the effects of utilization of nutrient substrates in surface water and remineralization below the euphotic zone. By combining the spatial variations of δ¹⁵N–NO₃ with δ¹⁵N-PN, we find that primary production in summer is mainly supported by regenerated nutrients, whether in the basin or in the slope. The effect of nitrification is only apparent in the slope due to its high productivity and active remineralization. δ¹⁵N-PN is not a good proxy of surface nitrate use, rather, it may reflect regional change of δ¹⁵N of ammonium, at least in summer.

分析了沿白令海西部横断面的上部 500 m 水柱中硝酸盐和悬浮颗粒氮 (PN) 的氮同位素组成，以表征夏季的氮循环。的δ ¹⁵硝酸盐的N（δ ¹⁵ N-NO ₃）增大到表面中，与硝酸盐浓度向上的下降，反映硝酸盐同化由浮游植物的效果很强的相关性。盆地和斜坡内硝酸盐同化作用（¹⁵ ε _NO3）的同位素效应估计分别为6.1±2.1‰和4.1±0.8‰。流域内¹⁵ ε _NO3的变化可能是由于浮游植物群落的差异，而斜坡中的¹⁵ ε _NO3被硝化作用低估了至少 1‰。有四种类型的δ之间关系的¹⁵ PN的N（δ ¹⁵ N-二PN）和溶解的无机氮浓度（[DIN]），即，一个恒定的低δ ¹⁵ N-二PN与稍微改变[DIN]在透光层盆地，在斜率的透光层的负相关性，在从透光层的温度最低层（T的底部的深度正相关_分钟层），以及相对恒定的δ ¹⁵ N-二PN在变[DIN] 低于 T _min层。这些关系反映了地表水中养分底物的利用和透光区以下再矿化的影响。通过结合δ ¹⁵ N-NO ₃和δ ¹⁵ N-PN的空间变化，我们发现夏季的初级生产主要由再生养分支持，无论是在盆地还是在斜坡。硝化作用仅在斜坡上表现出来，因为它的生产力高，再矿化活跃。δ ¹⁵ N-PN 不能很好地代表地表硝酸盐的使用，相反，它可能反映了铵的 δ ¹⁵ N 的区域变化，至少在夏季是这样。