Imprint of Trace Dissolved Oxygen on Prokaryoplankton Community Structure in an Oxygen Minimum Zone
Imprint of Trace Dissolved Oxygen on Prokaryoplankton Community Structure in an Oxygen Minimum Zone
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DOI：
10.3389/fmars.2020.00360
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发表时间：
2020-05-26
影响因子：
3.7
通讯作者：
Edgcomb, Virginia P.
中科院分区：
文献类型：
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作者：
Faull, Luis Medina;Mara, Paraskevi;Edgcomb, Virginia P.
热带北太平洋东部（ETNP）是一个大的、持续的、不断增强的氧气最小区（OMZ），几乎占全球OMZ总面积的一半。在OMZ核心（类似于350-700米深度）内，溶解氧通常接近或低于现代传感器的分析检测限（类似于10 nM）。OMZ核心上方和下方陡峭的氧气梯度导致微生物群落的垂直结构，这些微生物群落也在颗粒相关（PA）和自由生活（FL）粒度级之间变化。在这里，我们使用16 S扩增子测序（iTags）来分析FL和PA大小级分之间以及环境氧化还原条件范围内的原核生物种群的多样性和分布。在我们的研究区域的水文条件是不同的，从以前报道的ETNP和其他OMZ，如ETSP。痕量氧浓度（类似于0.35 μ M）存在于整个OMZ核心在我们的采样位置。因此，亚硝酸盐的积累通常报告OMZ核心是缺席的序列厌氧氨氧化细菌（Brocadiales属Bracidatus Scalindua），这是常见的跨缺氧-缺氧的边界在其他系统。然而，氨氧化细菌（AOB）和古细菌（AOA）的分布和最大的自养碳同化率（1.4 μ M C d（-1））与OMZ核心顶部附近的一个显着的铵浓度最大值相吻合。此外，亚硝酸盐氧化细菌（NOB）Glade属的成员，表明氨和亚硝酸盐氧化都发生在微量氧浓度。相似性检验（ANOSIM）和非度量维度标度（nMDS）分析表明，不同粒级之间细菌和古细菌的系统发育表现存在显着差异。基于ANOSIM和Flag配置文件，PA组合的组成是受当时的深度依赖的地球化学制度比FL分数的影响较小。基于AOA，NOB和微量氧的存在下，在OMZ核心，我们认为，硝化作用是一个积极的过程中，在氮循环的ETNP OMZ的这一地区。
The Eastern Tropical North Pacific (ETNP) is a large, persistent, and intensifying oxygen minimum zone (OMZ) that accounts for almost half of the total area of global OMZs. Within the OMZ core (similar to 350-700 m depth), dissolved oxygen is typically near or below the analytical detection limit of modern sensors (similar to 10 nM). Steep oxygen gradients above and below the OMZ core lead to vertical structuring of microbial communities that also vary between particle-associated (PA) and free-living (FL) size fractions. Here, we use 16S amplicon sequencing (iTags) to analyze the diversity and distribution of prokaryotic populations between FL and PA size fractions and among the range of ambient redox conditions. The hydrographic conditions at our study area were distinct from those previously reported in the ETNP and other OMZs, such as the ETSP. Trace oxygen concentrations (similar to 0.35 mu M) were present throughout the OMZ core at our sampling location. Consequently, nitrite accumulations typically reported for OMZ cores were absent as were sequences for anammox bacteria (Brocadiales genus Candidatus Scalindua), which are commonly found across oxic-anoxic boundaries in other systems. However, ammonia-oxidizing bacteria (AOB) and archaea (AOA) distributions and maximal autotrophic carbon assimilation rates (1.4 mu M C d(-1) ) coincided with a pronounced ammonium concentration maximum near the top of the OMZ core. In addition, members of the genus Nitrospina, a dominant nitrite-oxidizing bacterial (NOB) Glade were present suggesting that both ammonia and nitrite oxidation occur at trace oxygen concentrations. Analysis of similarity test (ANOSIM) and Non-metric Dimensional Scaling (nMDS) revealed that bacterial and archaeal phylogenetic representations were significantly different between size fractions. Based on ANOSIM and Flag profiles, composition of PA assemblages was less influenced by the prevailing depth-dependent biogeochemical regime than the FL fraction. Based on the presence of AOA, NOB and trace oxygen in the OMZ core we suggest that nitrification is an active process in the nitrogen cycle of this region of the ETNP OMZ.