Biological nitrogen fixation is increasingly recognized as an important source of new nitrogen in a warming ocean. However, the basin‐scale spatiotemporal distribution of nitrogen‐fixing organisms (diazotrophs) in the ocean and its controlling environmental factors remain unclear. Here we examined the basin‐scale seasonal distribution patterns of major diazotrophs (filamentous cyanobacterial Trichodesmium, unicellular cyanobacterial UCYN‐A1, and proteobacterial Gamma‐A) in surface waters of the North Pacific from 2014 to 2016 with unprecedented coverage and resolution. In general, UCYN‐A1, Trichodesmium, and Gamma‐A were abundant during spring‐autumn, summer‐autumn, and spring respectively. Regarding latitudinal patterns of abundance, UCYN‐A1 showed dome shape; Trichodesmium was gradually decreasing from low‐ to high‐latitude regions; and Gamma‐A did not show a clear pattern, which were coincident with the distinct correlations between the diazotrophs and temperature. All three diazotrophs were abundant (reached 10⁶–10⁷ nifH gene copy number L⁻¹) in the North Pacific transition zone and subtropical gyre, where the cyanobacterial diazotrophs were more abundant in both the western and eastern North Pacific than in the central North Pacific. The diazotroph abundance in the western North Pacific was positively correlated with eddy kinetic energy and sea surface height anomaly, which implies an enhancement of diazotrophs in mesoscale eddies associated with the western boundary current Kuroshio and its extension. The cyanobacterial diazotrophs were positively correlated with wind stress curl, a measurable parameter of wind‐driven upwelling, in the eastern North Pacific. Our study refines the biogeography of three major diazotrophs and highlights the importance of physical forcing in mediating their dynamics.

中文翻译：

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物理强迫控制北太平洋洋盆级固氮生物的发生

生物固氮越来越多地被认为是变暖海洋中新氮的重要来源。然而，海洋中固氮生物（固氮生物）在盆地规模的时空分布及其控制环境因素仍不清楚。在这里，我们研究了2014年至2016年北太平洋地表水中主要重氮菌（丝状蓝细菌Trichodesmium，单细胞蓝细菌UCYN-A1和蛋白细菌Gamma-A）的流域尺度季节性分布模式，其覆盖范围和分辨率都达到了前所未有的水平。通常，UCYN-A1，Trichodesmium和Gamma-A在春季-秋季，夏季-秋季和春季分别丰富。关于纬度的丰度模式，UCYN-A1显示出圆顶形状；线粒体从低纬度到高纬度逐渐减少。Gamma-A并未显示出清晰的模式，这与重氮与温度之间的明显相关性相吻合。所有三个重氮营养菌都很丰富（达到10 ⁶ –10 ⁷ nifH基因拷贝数L ^-1）在北太平洋过渡带和亚热带回旋区，在那里北太平洋西部和东部的蓝细菌重氮营养比北太平洋中部的丰富。北太平洋西部重氮营养体的丰度与涡动能和海面高度异常呈正相关，这意味着与西部边界流黑潮及其扩展有关的中尺度涡旋中重氮营养体的增加。在北太平洋东部，蓝藻重氮菌与风应力卷曲呈正相关，风应力卷曲是风向上升的可测量参数。我们的研究完善了三种主要的重氮营养生物的生物地理学，并强调了物理强迫在介导其动力学方面的重要性。