Latitudinal constraints on the abundance and activity of the cyanobacterium UCYN-A and other marine diazotrophs in the North Pacific
Latitudinal constraints on the abundance and activity of the cyanobacterium UCYN-A and other marine diazotrophs in the North Pacific
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DOI：
10.1002/lno.11423
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发表时间：
2020-03-05
影响因子：
4.5
通讯作者：
Zehr, Jonathan P.
中科院分区：
文献类型：
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作者：
Gradoville, Mary R.;Farnelid, Hanna;Zehr, Jonathan P.
已知的海洋环境中含有固氮(N-2)(重氮营养)微生物的数量正在增加，这促使人们重新评估海洋重氮菌的生物地理学和N(2)固定率(NFR)。在这里，我们调查了北太平洋亚热带环流(NPSG)和北太平洋过渡带(NPTZ)的固氮微生物的多样性、丰度和活性，NPSG是一个重氮化的栖息地，北太平洋过渡带(NPTZ)具有强烈的物理、化学和生物梯度。2016年和2017年在两次春季经向巡航上采集了样本，范围从北纬23.5度到北纬41.4度，沿158度西经。我们在NPTZ南缘附近观察到重氮营养丰富度突然下降，这与盐度锋面相吻合，聚球藻丰度增加了近10倍，但磷酸盐或硝酸盐浓度没有随之变化。在这条重氮营养界线以南的NPSG水域中，nifH基因和nfRs被一致检测到，重氮营养群落以未培养的共生蓝藻Ucyn-A为主(nifH基因拷贝数为L-1)。定量聚合酶链式反应衍生的UCyN-AnifH基因丰度与NPSG中群落NFR呈显著正相关，提示UCyN-A对群落NFR有较大贡献。在以北的NPTZ水域中，NFR很低或未检测到，nifH基因很少，只有很少的检测到的序列以UCyn-A和非蓝藻重氮菌为代表。我们在当地生物地球化学背景下观察到的UCyn-A丰度的模式表明，这种生物的环境控制可能不同于培养的海洋蓝藻重氮养生物。
The number of marine environments known to harbor dinitrogen (N-2)-fixing (diazotrophic) microorganisms is increasing, prompting a reassessment of the biogeography of marine diazotrophs and N(2)fixation rates (NFRs). Here, we investigate the diversity, abundance, and activity of diazotrophic microorganisms in the North Pacific Subtropical Gyre (NPSG), a diazotrophic habitat, and the North Pacific Transition Zone (NPTZ), a region characterized by strong physical, chemical, and biological gradients. Samples were collected on two springtime meridional cruises during 2016 and 2017, spanning from 23.5 degrees N to 41.4 degrees N along 158 degrees W. We observed an abrupt decrease in diazotrophic abundances near the southern edge of the NPTZ, which coincided with a salinity front and with a similar to 10-fold increase inSynechococcusabundance, but without a concomitant change in phosphate or nitrate concentrations. In NPSG waters south of this diazotrophic boundary,nifHgenes and NFRs were consistently detected and diazotrophic communities were dominated by UCYN-A, an uncultivated, symbiotic cyanobacterium (2.8 x 10(3)to 1.0 x 10(6)nifHgene copies L-1). There was a significant positive relationship between quantitative polymerase chain reaction-derived UCYN-AnifHgene abundances and community NFRs in the NPSG, suggesting a large contribution of UCYN-A to community NFRs. In the NPTZ waters to the north, NFRs were low or undetected andnifHgenes were rare, with the few detected sequences represented by UCYN-A and noncyanobacterial diazotrophs. The patterns we observed in UCYN-A abundance in the context of local biogeochemistry suggest that the environmental controls of this organism may differ from those of cultivated marine cyanobacterial diazotrophs.