River ecosystems are critical for human and environmental health, with bacterioplankton playing a vital role in biogeochemical cycles. Unveiling the spatial patterns of bacterioplankton communities in relation to environmental factors is important for understanding the processes of microbial variation and functional maintenance. However, our understanding of the correlations among bacterioplankton communities, physicochemical factors, and land use, especially in large rivers affected by intensive anthropogenic activities, remains relatively poor. Here, we investigated the bacterioplankton communities in July 2018 in three main tributaries of the Pearl River, i.e., Beijiang, Xijiang, and Pearl River Delta, based on 16S rRNA high-throughput sequencing. Results showed that the most dominant phyla, Proteobacteria, Actinobacteria, Cyanobacteria, and Planctomycetes accounted for 33.75%, 22.15%, 11.65%, and 10.48% of the total abundance, respectively. The bacterioplankton communities showed remarkable differences among the three tributaries in terms of composition, structure, diversity, and predictive functional profiles. Mantel and partial Mantel tests revealed that the bacterioplankton communities were affected by physicochemical variables (p < 0.01) and land use (p < 0.01). Redundancy analysis identified specific conductivity, dissolved oxygen, agricultural land, ammonium, urban land, and water transparency as the dominant environmental factors influencing the bacterioplankton communities in the Pearl River. Variation partitioning analysis indicated that both physicochemical factors and land use had direct effects on the bacterioplankton community, and that land use may also shape bacterioplankton communities through indirect effects of physicochemical factors on riverine ecosystems. This study provides fundamental information on the diversity, spatial patterns, and influencing factors of bacterioplankton communities in the Pearl River, which should enhance our understanding of how such communities change in response to environmental gradients and anthropogenic activities.

中文翻译：

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珠江三角洲浮游细菌群落的空间变化：土地利用和理化因素的影响。

河流生态系统对人类和环境健康至关重要，浮游细菌在生物地球化学循环中起着至关重要的作用。揭示与环境因素有关的浮游细菌群落的空间格局对于理解微生物变异和功能维持过程非常重要。但是，我们对浮游植物群落，理化因素和土地利用之间的相关性的理解仍然相对较差，特别是在受到密集的人为活动影响的大河中。在这里，我们基于16S rRNA高通量测序研究了2018年7月在珠江的三个主要支流，即北江，西江和珠江三角洲的浮游细菌群落。结果显示，最主要的菌群是Proteobacteria，Actinobacteria，Cyanobacteria，浮游菌分别占总丰度的33.75％，22.15％，11.65％和10.48％。在组成，结构，多样性和可预测的功能特征方面，浮游细菌群落在三个支流之间表现出显着差异。壁炉架和部分壁炉架测试表明，浮游生物群落受到理化变量的影响（p <0.01）和土地利用（p<0.01）。冗余分析确定了比电导率，溶解氧，农用土地，铵，城市土地和水的透明性是影响珠江浮游细菌群落的主要环境因素。变异分区分析表明，理化因子和土地利用均直接影响浮游植物群落，土地利用也可能通过理化因素对河流生态系统的间接影响而影响浮游植物群落。这项研究提供了有关珠江中浮游细菌群落多样性，空间格局及其影响因素的基本信息，这应该加深我们对此类细菌群落如何响应环境梯度和人为活动而变化的理解。