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Abstract：
Marine bacterial community plays a vital role in the formation of the hypoxia zone in coastal oceans. Yet, their dynamics in the seasonal hypoxia zone of the Bohai Sea (BHS) are barely studied. Here, the 16S rRNA gene-based high-throughput sequencing was used to explore the dynamics of their diversity, structure, and function as well as driving factors during the gradual deoxygenation process in the BHS. Our results evinced that the bacterial community was dominated by Proteobacteria, followed by Bacteroidetes, Firmicutes, Actinobacteria, and Cyanobacteria, etc. The abundant subcommunity dominated in the number of sequences (49%) while the rare subcommunity dominated in the number of species (99.61%). Although abundant subcommunity accounted for most sequences, rare subcommunity possessed higher diversity, richness and their population dramatically changed (higher turnover) during the hypoxia transition. Further, co-occurrence network analysis proved the vital role of rare subcommunity in the process of community assembly. Additionally, beta diversity partition revealed that both subcommunities possessed a higher turnover component than nestedness and/or richness component, implying species replacement could explain a considerable percentage of community variation. This variation might be governed by both environmental selection and stochastic processes, and further, it influenced the nitrogen cycle (PICRUSt-based prediction) of the hypoxia zone. Overall, this study provides insight into the spatial-temporal heterogeneity of bacterial and their vital role in biogeochemical cycles in the hypoxia zone of the BHS. These findings will extend our horizons about the stabilization mechanism, feedback regulation, and interactive model inside the bacterial community under oxygen-depleted ecosystems.
摘要：
海洋细菌群落在沿海海洋缺氧区的形成中起着至关重要的作用。然而，它们在渤海季节性缺氧区（BHS）的动态几乎没有研究。这里,基于16SrRNA基因的高通量测序用于探索其多样性的动态，结构,在BHS的逐渐脱氧过程中，其功能以及驱动因素。我们的研究结果表明，细菌群落以变形杆菌为主，其次是拟杆菌，Firmicutes,放线菌,和蓝细菌，等。丰富的亚群落在序列数量中占主导地位（49％），而稀有的亚群落在物种数量中占主导地位（99.61％）。尽管丰富的亚群落占大多数序列，稀有亚群落具有较高的多样性，在缺氧过渡期间，丰富度和他们的人口发生了戏剧性的变化(更高的营业额)。Further,共现网络分析证明了罕见亚社区在社区聚集过程中的重要作用。此外,β多样性分区显示，两个亚群落都具有比嵌套和/或丰富度更高的周转成分，暗示物种替换可以解释相当大比例的群落变异。这种变化可能受环境选择和随机过程的控制，进一步,它影响了缺氧区的氮循环（基于PICRUSt的预测）。总的来说,这项研究提供了深入了解细菌的时空异质性及其在BHS缺氧区生物地球化学循环中的重要作用。这些发现将扩大我们对稳定机制的视野，反馈调节，和耗氧生态系统下细菌群落内部的相互作用模型。
