Institute of Marine Science and Technology, Shandong University, Jinan, 250110, China.
Department of Biological Sciences, University of Southern California, Los Angeles, California, 90089, USA.
Sci Rep. 2018 Feb 5;8(1):2415. doi: 10.1038/s41598-018-20743-0.
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. N 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 N 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 N fixation rates of Trichodesmium ranged from 0.11 to 9.83 pmolNtrichome d with an average of 4.03 pmolNtrichome d. The Luzon Strait and the ECS Kuroshio had higher N 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 N 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.
2009 年 7 月 16 日至 9 月 1 日期间，研究了南海北部（nSCS）和黑潮中的固氮菌的分布及其固氮活性。通过乙炔还原法测定了整个海水和表层<10 μm 颗粒中的氮固定活性。东海黑潮和南海北部陆架的活性较高。南海北部盆地的氮固定活性较低。<10 μm 颗粒（单细胞固氮菌）在整个调查期间对整个水体的活性贡献较大，表明纳米浮游蓝细菌是调查区域的主要固氮菌。束毛藻的日固氮率范围为 0.11 至 9.83 pmolNtrichome d，平均值为 4.03 pmolNtrichome d。吕宋海峡和东海黑潮的束毛藻固氮率高于南海北部陆架和盆地。与整个水体相比，大多数站位的束毛藻活性计算值中等偏低。整个水体的固氮对初级生产力的贡献范围为 1.7%至 18.5%。束毛藻引入的新氮量估计占吕宋海峡总初级生产力的 0.14%，占新生产力的 0.41%。
