N2 fixation rate and diazotroph community structure in the western tropical North Pacific Ocean (WTNP)
N2 fixation rate and diazotroph community structure in the western tropical North Pacific Ocean (WTNP)
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热带北太平洋西部（WTNP）的 N2 固定率和固氮生物群落结构
DOI：
10.1007/s13131-019-1513-4
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发表时间：
2019
影响因子：
1.4
通讯作者：
Wang Chunsheng
中科院分区：
文献类型：
--
作者：
Zhang Run;Zhang Dongsheng;Chen Min;Jiang Zhibing;Wang Chunsheng
在本研究中，我们报告了热带北太平洋（WTNP）西部（13°-20°N, 120°-160°E）的氮固定率（15N同位素示踪法）和重氮营养菌群落结构（使用分子方法）。我们基于原位固氮活性和重氮营养菌群落结构的独立证据表明，在采样期间，大多数WTNP地表水以单细胞固氮为主。此外，重氮营养成分的转变，从单细胞蓝藻群b为主到trichodesmiumspp。2013年也观测到以-为主的西边界流（黑潮）。我们假设养分有效性可能在调节氮固定的生物地理中起主要作用。在表层水体中，体积固氮速率（以氮计算）在0.6 ~ 2.6 nmol/（L·d）之间，平均为（1.2±0.5）nmol/(L·d)，在135°E ~ 160°E的总速率中，<10 μm粒径组分占主导地位（88%±6%）。200 m以上深度综合氮固定速率在150 ~ 480 μmol/（m2·d）之间，平均为（225±105）μmol/（m2·d）。n2固定占深度综合初级产量的6.2%±3.7%，表明n2固定是维持WTNP新产量和出口产量的重要氮源。在气候变化脆弱地区，固氮在生物地球化学循环中的作用有待进一步研究。
In the present study, we report N2fixation rate (15N isotope tracer assay) and the diazotroph community structure (using the molecular method) in the western tropical North Pacific Ocean (WTNP) (13°–20°N, 120°–160°E). Our independent evidence on the basis of bothin situN2fixation activity and diazotroph community structure showed the dominance of unicellular N2fixation over majority of the WTNP surface waters during the sampling periods. Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated toTrichodesmiumspp.-dominated toward the western boundary current (Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N2fixation. In surface waters, volumetric N2fixation rate (calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged (1.2±0.5) nmol/(L·d), with <10 μm size fraction contributed predominantly (88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N2fixation rate over the upper 200 m ranged between 150 μmol/(m2·d) and 480 μmol/(m2·d) (average (225±105) μmol/(m2·d). N2fixation can account for 6.2%±3.7% of the depth-integrated primary production, suggesting that N2fixation is a significant N source sustaining new and export production in the WTNP. The role of N2fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.