N₂ fixation rates (NFR, in terms of N) in the northern South China Sea (nSCS) and the East China Sea (ECS) were measured using the acetylene reduction assay in summer and winter, 2009. NFR of the surface water ranged from 1.14 nmol/(L·d) to 10.40 nmol/(L·d) (average at (4.89±3.46) nmol/(L·d), n=11) in summer and 0.74 nmol/(L·d) to 29.45 nmol/(L·d) (average at (7.81±8.50) nmol/(L·d), n=15) in winter. Significant spatio-temporal heterogeneity emerged in our study: the anticyclonic eddies (AE) (P<0.01) and the Kuroshio Current (KC) (P<0.05) performed significantly higher NFR than that in the cyclonic eddies or no-eddy area (CEONE), indicating NFR was profoundly influenced by the physical process of the Kuroshio and mesoscale eddies. The depth-integrated N₂ fixation rates (INF, in terms of N) ranged from 52.4 µmol/(m²·d) to 905.2 µmol/(m²·d) (average at (428.9±305.5) µmol/(m²·d), n=15) in the winter. The contribution of surface NFR to primary production (PP) ranged from 1.7% to 18.5% in the summer, and the mean contribution of INF to new primary production (NPP) in the nSCS and ECS were estimated to be 11.0% and 36.7% in the winter. The contribution of INF to NPP (3.0%–93.9%) also decreased from oligotrophic sea toward the eutrophic waters affected by runoffs or the CEONE. Furthermore, we observed higher contributions compared to previous studies, revealing the vital roles of nitrogen fixation in sustaining the carbon pump of the nSCS and ECS.

在2009年夏季和冬季，使用乙炔还原法测量了南海北部（nSCS）和东海（ECS）中的N ₂固定率（以N换算）。地表水的NFR范围为夏季为1.14 nmol /（L·d）至10.40 nmol /（L·d）（平均值为（4.89±3.46）nmol /（L·d），n = 11），而0.74 nmol /（L·d）为29.45 nmol /（L·d）（冬季平均（7.81±8.50）nmol /（L·d），n = 15）。在我们的研究中出现了显着的时空异质性：反气旋涡（AE）（P <0.01）和黑潮潮流（KC）（P<0.05）的NFR明显高于旋风涡流或非涡旋区（CEONE），表明NFR受到黑潮和中尺度涡旋的物理过程的深刻影响。深度积分的N ₂固定率（INF，以N表示）为52.4 µmol /（m ² ·d）至905.2 µmol /（m ² ·d）（平均为（428.9±305.5）µmol /（m ² ·d），n= 15）在冬天。夏季，地表NFR对初级生产（PP）的贡献从1.7％到18.5％不等，据估计，在nSCS和ECS中，INF对新初级生产（NPP）的平均贡献为11.0％和36.7％。冬天。INF对NPP的贡献（3.0％–93.9％）也从寡营养海向受径流或CEONE影响的富营养水下降。此外，与之前的研究相比，我们观察到了更高的贡献，揭示了固氮在维持nSCS和ECS碳泵中的重要作用。