Microbial community structure in the western tropical South Pacific
Microbial community structure in the western tropical South Pacific
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DOI：
10.5194/bg-15-3909-2018
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发表时间：
2018-06-29
期刊：
影响因子：
4.9
通讯作者：
Duhamel, Solange
中科院分区：
文献类型：
--
作者：
Bock, Nicholas;Van Wambeke, France;Duhamel, Solange
寡养区在全球生物地球化学循环中发挥着核心作用，这些地区的微生物群落代表着全球碳收支中的一个重要术语。虽然全球海洋中微生物群落的一般结构已经有了很好的记录，但一些偏远地区，如热带南太平洋西部(WTSP)，从根本上仍然没有被探索。此外，制约微生物丰度和分布的生物和非生物因素仍然没有得到很好的解决。在这项研究中，我们量化了2015年夏季WTSP样带上主要浮游生物种群的空间(垂直和水平)分布，捕获了重要的自养和异养组合，包括细胞计量学确定的非色素原生动物(也称为鞭毛虫)的丰度。使用环境参数(例如，养分和光照可用性)以及统计分析，我们估计了自下而上和自上而下的控制在限制WTSP微生物群落结构方面的作用，这些微生物群落位于生物地球化学不同的区域。在最一般的层面上，我们发现了一种“典型的热带结构”，其特征是浅混合层，所有采样点都有明显的深叶绿素峰值，以及深的硝化线。样带内原氯球藻类尤其丰富，占浮游植物生物量的68+/-10.6%。尽管其丰度相对较低，但超微植物真核生物(PPE)在深度整合浮游植物生物量中所占比例高达26+/-11.6%，而聚球藻仅占6+/-6.9%。我们的结果表明，WTSP的微生物群落结构是典型的高度分层的区域，并强调了PPE种群对总生物量的重要贡献。N-2固定率与浮游生物丰度之间的强烈关系表明，在WTSP中，N-2固定化在调节生态系统过程中发挥着核心作用，而对丰度数据的比较分析表明，在营养限制下，微生物群落结构越来越多地受到自下而上过程的调节，可能是为了应对高核酸细菌(HNA)丰度的变化。
Oligotrophic regions play a central role in global biogeochemical cycles, with microbial communities in these areas representing an important term in global carbon budgets. While the general structure of microbial communities has been well documented in the global ocean, some remote regions such as the western tropical South Pacific (WTSP) remain fundamentally unexplored. Moreover, the biotic and abiotic factors constraining microbial abundances and distribution remain not well resolved. In this study, we quantified the spatial (vertical and horizontal) distribution of major microbial plankton groups along a transect through the WTSP during the austral summer of 2015, capturing important autotrophic and heterotrophic assemblages including cytometrically determined abundances of non-pigmented protists (also called flagellates). Using environmental parameters (e.g., nutrients and light availability) as well as statistical analyses, we estimated the role of bottom-up and top-down controls in constraining the structure of the WTSP microbial communities in biogeochemically distinct regions. At the most general level, we found a "typical tropical structure", characterized by a shallow mixed layer, a clear deep chlorophyll maximum at all sampling sites, and a deep nitracline. Prochlorococcus was especially abundant along the transect, accounting for 68 +/- 10.6% of depth-integrated phytoplankton biomass. Despite their relatively low abundances, pico-phytoeukaryotes (PPE) accounted for up to 26 +/- 11.6% of depth-integrated phytoplankton biomass, while Synechococcus accounted for only 6 +/- 6.9 %. Our results show that the microbial community structure of the WTSP is typical of highly stratified regions, and underline the significant contribution to total biomass by PPE populations. Strong relationships between N-2 fixation rates and plankton abundances demonstrate the central role of N-2 fixation in regulating ecosystem processes in the WTSP, while comparative analyses of abundance data suggest microbial community structure to be increasingly regulated by bottom-up processes under nutrient limitation, possibly in response to shifts in abundances of high nucleic acid bacteria (HNA).