Nitrogen fixation and the diazotroph community in the temperate coastal region of the northwestern North Pacific
Nitrogen fixation and the diazotroph community in the temperate coastal region of the northwestern North Pacific
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DOI：
10.5194/bg-12-4751-2015
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发表时间：
2015-08
期刊：
影响因子：
4.9
通讯作者：
T. Shiozaki;T. Nagata;M. Ijichi;K. Furuya
中科院分区：
文献类型：
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作者：
T. Shiozaki;T. Nagata;M. Ijichi;K. Furuya
抽象。氮固定在温带海洋是一个潜在的重要，但了解甚少的过程，可能会影响海洋氮收支。本研究确定了北太平洋西北部温带沿海地区真光层固氮和固氮生物群落的季节变化。从初夏到秋季，当表面温度超过14.2 °C（但低于24.3 °C）且表面硝酸盐浓度低（≤ 0.30 μM）时，测得的固氮高达13.6 nmol N L−1 d−1，尽管我们也在硝酸盐浓度高（> 1 μM）的次表层（42-62 m）检测到固氮。克隆文库分析结果表明，nifH基因序列是无所不在的整个调查期间。在检测到固氮作用的时期（初夏至秋季），UCYN-A、束毛霉属和γ-变形菌属γ-24774 A11的基因频繁恢复。与此相反，当固氮是不可检测的（冬季至春季），许多序列属于集群III固氮菌（假定的厌氧细菌）恢复。定量PCR分析表明，UCYN-A在初夏至夏末的丰度相对较高，而束毛藻和γ-24774A11在秋季的丰度最高。
Abstract. Nitrogen fixation in temperate oceans is a potentially important, but poorly understood process that may influence the marine nitrogen budget. This study determined seasonal variations in nitrogen fixation and the diazotroph community within the euphotic zone in the temperate coastal region of the northwestern North Pacific. Nitrogen fixation as high as 13.6 nmol N L−1 d−1 was measured from early summer to fall when the surface temperature exceeded 14.2 °C (but was lower than 24.3 °C) and the surface nitrate concentration was low (≤ 0.30 μM), although we also detected nitrogen fixation in subsurface layers (42–62 m) where nitrate concentrations were high (> 1 μM). Clone library analysis results indicated that nifH gene sequences were omnipresent throughout the investigation period. During the period when nitrogen fixation was detected (early summer to fall), the genes affiliated with UCYN-A, Trichodesmium, and γ-proteobacterial phylotype γ-24774A11 were frequently recovered. In contrast, when nitrogen fixation was undetectable (winter to spring), many sequences affiliated with Cluster III diazotrophs (putative anaerobic bacteria) were recovered. Quantitative PCR analysis revealed that UCYN-A was relatively abundant from early to late summer compared with Trichodesmium and γ-24774A11, whereas Trichodesmium abundance was the highest among the three groups during fall.