In Situ Diazotroph Population Dynamics Under Different Resource Ratios in the North Pacific Subtropical Gyre.
In Situ Diazotroph Population Dynamics Under Different Resource Ratios in the North Pacific Subtropical Gyre.
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DOI：
10.3389/fmicb.2018.01616
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发表时间：
2018
影响因子：
5.2
通讯作者：
Zehr JP
中科院分区：
文献类型：
--
作者：
Turk-Kubo KA;Connell P;Caron D;Hogan ME;Farnelid HM;Zehr JP
在过去几十年中，在了解海洋固氮微生物（重氮营养体）的多样性、分布和活动方面取得了重大进展，然而，在环境对其生长和死亡率的控制方面仍然存在很大的知识差距。为测定重氮营养体净生长率和浮游微动物对重氮营养体的掠食率，于2016年3月在ALOHA站附近采用自由漂浮原位孵育阵列进行了营养扰动实验和稀释掠食实验。在高(H)和低(L)硝酸盐：磷酸盐（NP）比条件下，在25、45、75和100 m的四个光区深度，采用定量PCR和流式细胞术测定了重氮营养目标分类群以及原绿球藻、聚藻球菌和光合微真核生物的净生长率。采用16S rRNA可变区标记测序技术，分析了HNP和LNP处理对原核生物群落组成的影响。利用改进的稀释技术，在15和125 m的两个光区深度测量了浮游微动物对重氮营养体的掠食率。大多数重氮营养体在48 h后的净生长率并没有像预期的那样受到LNP条件的刺激，相反，在HNP处理中经常测量到提高的生长率。有趣的是，在75和100 m处，HNP处理刺激了未培养的原水生共生体UCYN-A1的净生长率，这表明用于生长的氮是通过在硝酸盐存在的情况下继续固定N2获得的。UCYN-A1、UCYN-C、Crocosphaera sp. （UCYN-B）和硅藻共生体Richelia（与根管菌相关）的净生长率在45 m处一致较高（可达1.6±0.5 d-1），这表明在实验开始时，在该深度均处于最佳生长状态。15 m水域浮游微动物对UCYN-A1和UCYN-C的掠食率差异表明，捕食者组合优先捕食UCYN-A1。在水柱深处（125 m），两种重氮营养体都以相当高的速率被放牧，这表明放牧压力可能随着光带深度的增加而增加。限制原位重氮营养体的生长和死亡率是改善全球生态系统模型中重氮营养体参数化的重要步骤。
Major advances in understanding the diversity, distribution, and activity of marine N2-fixing microorganisms (diazotrophs) have been made in the past decades, however, large gaps in knowledge remain about the environmental controls on growth and mortality rates. In order to measure diazotroph net growth rates and microzooplankton grazing rates on diazotrophs, nutrient perturbation experiments and dilution grazing experiments were conducted using free-floating in situ incubation arrays in the vicinity of Station ALOHA in March 2016. Net growth rates for targeted diazotroph taxa as well as Prochlorococcus, Synechococcus and photosynthetic picoeukaryotes were determined under high (H) and low (L) nitrate:phosphate (NP) ratio conditions at four depths in the photic zone (25, 45, 75, and 100 m) using quantitative PCR and flow cytometry. Changes in the prokaryote community composition in response to HNP and LNP treatments were characterized using 16S rRNA variable region tag sequencing. Microzooplankton grazing rates on diazotrophs were measured using a modified dilution technique at two depths in the photic zone (15 and 125 m). Net growth rates for most of the targeted diazotrophs after 48 h were not stimulated as expected by LNP conditions, rather enhanced growth rates were often measured in HNP treatments. Interestingly, net growth rates of the uncultivated prymnesiophyte symbiont UCYN-A1 were stimulated in HNP treatments at 75 and 100 m, suggesting that N used for growth was acquired through continuing to fix N2 in the presence of nitrate. Net growth rates for UCYN-A1, UCYN-C, Crocosphaera sp. (UCYN-B) and the diatom symbiont Richelia (associated with Rhizosolenia) were uniformly high at 45 m (up to 1.6 ± 0.5 d-1), implying that all were growing optimally at the onset of the experiment at that depth. Differences in microzooplankton grazing rates on UCYN-A1 and UCYN-C in 15 m waters indicate that the grazer assemblage preyed preferentially on UCYN-A1. Deeper in the water column (125 m), both diazotrophs were grazed at substantial rates, suggesting grazing pressure may increase with depth in the photic zone. Constraining in situ diazotroph growth and mortality rates are important steps for improving parameterization for diazotrophs in global ecosystem models.
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影响因子：
5.2
作者：
Dutkiewicz, S.;Follows, M. J.;Bragg, J. G.
通讯作者：
Bragg, J. G.
影响因子：
4.9
作者：
Bonnet, Sophie;Berthelot, Hugo;Berman-Frank, Ilana
通讯作者：
Berman-Frank, Ilana
影响因子：
3.7
作者：
Fernandez C;Farías L;Ulloa O
通讯作者：
Ulloa O
影响因子：
4.4
作者：
Falcón, LI;Carpenter, EJ;Capone, DG
通讯作者：
Capone, DG
影响因子：
11
作者：
Bentzon-Tilia, Mikkel;Traving, Sachia J.;Riemann, Lasse
通讯作者：
Riemann, Lasse