Basin scale variability of active diazotrophs and nitrogen fixation in the North Pacific, from the tropics to the subarctic Bering Sea
Basin scale variability of active diazotrophs and nitrogen fixation in the North Pacific, from the tropics to the subarctic Bering Sea
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DOI：
10.1002/2017gb005681
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发表时间：
2017-06
影响因子：
5.2
通讯作者：
T. Shiozaki;Deniz Bombar;L. Riemann;F. Hashihama;S. Takeda;T. Yamaguchi;Makoto Ehama;K. Hamasaki
中科院分区：
文献类型：
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作者：
T. Shiozaki;Deniz Bombar;L. Riemann;F. Hashihama;S. Takeda;T. Yamaguchi;Makoto Ehama;K. Hamasaki
固氮微生物(重氮菌)为浮游生物群落提供生物可利用的氮，从而极大地影响许多海洋区域的生产力。传统上，不同的蓝藻类群被认为是主要的海洋重氮细菌，但后来非蓝藻和可能的异养重氮细菌也被发现广泛存在，并在固氮方面具有潜在的重要作用。然而，对于大多数海洋生态系统来说，不同的重氮菌类群的分布和活动仍然受到很少的限制。在这里，我们研究了赤道太平洋中部和白令海之间7500公里南北断面上的重氮菌群落结构和活动。在亚热带环流的上游水域，固氮贡献了高达84%的新产量，那里的重固氮菌群落包括伽马蛋白细菌γ-24774A11和高度活跃的蓝藻系统类型(占总nifH转录本丰度的50%)。有时在150米深处可以检测到固氮，并在35°N左右水平延伸到环流边缘，甚至在遥远的北边的白令海陆架上也检测到固氮。在白令海陆架的阿拉斯加沿岸水域，低硝酸盐和高溶解铁浓度似乎促进了重氮菌的生长，其中UCyN-A2的作用突出，在表层丰富(1.2×105nifH基因拷贝L−1)。我们的研究为白令海的固氮提供了证据，并表明热带/副热带环流与北太平洋北部寒冷地区单独水域的重氮菌组成存在明显的对比。
Nitrogen‐fixing microorganisms (diazotrophs) provide biologically available nitrogen to plankton communities and thereby greatly influence the productivity in many marine regions. Various cyanobacterial groups have traditionally been considered the major oceanic diazotrophs, but later noncyanobacterial and presumably heterotrophic diazotrophs were also found to be widespread and potentially important in nitrogen fixation. However, the distribution and activity of different diazotroph groups is still poorly constrained for most oceanic ecosystems. Here we examined diazotroph community structure and activity along a 7500 km south‐north transect between the central equatorial Pacific and the Bering Sea. Nitrogen fixation contributed up to 84% of new production in the upper waters of the subtropical gyre, where the diazotroph community included the gammaproteobacterium γ‐24774A11 and highly active cyanobacterial phylotypes (>50% of total nifH transcript abundance). Nitrogen fixation was sometimes detectable down to 150 m depth and extended horizontally to the edge of the gyre at around 35°N. Nitrogen fixation was even detected far north on the Bering Sea shelf. In the Alaskan Coastal Waters on the Bering Sea shelf, low nitrate together with high dissolved iron concentrations seemed to foster diazotroph growth, including a prominent role of UCYN‐A2, which was abundant near the surface (1.2×105 nifH gene copies L−1). Our study provides evidence for nitrogen fixation in the Bering Sea and suggests a clear contrast in the composition of diazotrophs between the tropical/subtropical gyre and the separate waters in the cold northern regions of the North Pacific.