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>Nitrogen Fixation by Trichodesmium and unicellular diazotrophs in the northern South China Sea and the Kuroshio in summer
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Nitrogen Fixation by Trichodesmium and unicellular diazotrophs in the northern South China Sea and the Kuroshio in summer
Distribution of diazotrophs and their nitrogen fixation activity were investigated in the northern South China Sea (nSCS) and the Kuroshio from July 16th to September 1st, 2009. N2 fixation activities in whole seawater and <10 μm fraction at the surface were measured by acetylene reduction assay. Higher activities were observed at the East China Sea (ECS) Kuroshio and the nSCS shelf. The nSCS basin showed a low N2 fixation activity. The <10 μm fractions (unicellular diazotrophs) contributed major portion to the whole-water activity in the survey time, indicating that nanoplanktonic cyanobacterias were the major diazotrophs in the survey area. Daily N2 fixation rates of Trichodesmium ranged from 0.11 to 9.83 pmolNtrichome−1 d−1 with an average of 4.03 pmolNtrichome−1 d−1. The Luzon Strait and the ECS Kuroshio had higher N2 fixation rates of Trichodesmium than the nSCS shelf and basin. Calculated activities of Trichodesmium at most stations were moderately low compared with that of the whole-water. The contribution of N2 fixation by the whole-water to primary production ranged from 1.7% to 18.5%. The estimated amount of new nitrogen introduced by Trichodesmium contributed up to 0.14% of the total primary production and 0.41% of the new production in the Luzon Strait.
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机译：2009年7月16日至9月1日在南海北部和黑潮研究了重氮营养菌的分布及其固氮活性。通过乙炔还原法测量了整个海水中N2的固着活性和表面<10μm的N2固着力。分析。在东海黑潮和nSCS架子上观测到了更高的活动。 nSCS盆地显示出较低的N2固定活性。在调查时间内，<10μm的组分（单细胞重氮菌）是全水活动的主要部分，这表明纳米浮游藻蓝细菌是调查区的主要重氮菌。毛滴虫的每日N2固定率介于0.11至9.83 pmolNtrichome -1 d -1 ，平均为4.03 pmolNtrichome -1 d -1 。吕宋海峡和ECS黑潮的Trichodesmium固氮率高于nSCS架子和盆地。与全水相比，大多数站点的毛滴虫的计算活动量都较低。全水固氮对初级生产的贡献在1.7％至18.5％之间。 Trichodesmium引入的新氮的估计量占吕宋海峡初级生产总量的0.14％和新生产的0.41％。
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