Due to the recent decades of climate change and intensive human activities, endorheic lakes are threatened by both salinization and eutrophication. However, knowledge of the aquatic bacterial community’s response to simultaneous increasing salinity and trophic status is still poor. To address this knowledge gap, we collected 40 surface water samples from five lakes and six rivers on the semi-arid Inner Mongolia Plateau, and investigated their bacterial communities using 16S rRNA gene-targeted amplicon sequencing. We found that bacterial species diversity significantly decreased from the mesotrophic freshwater river habitat to the eutrophic high-brackish lake habitat; salinity was more important than trophic status in explaining this decreased diversity. Salinity was the most important environmental factor in shaping community composition, while increased nitrogen loading was more important in structuring predicted functional composition. Within the lake habitats, the impact of environmental filtering on bacterial community assembly increased with the increasing salinity. The results suggested that the elevated salinity and nutrients have combined effects on the aquatic bacterial community, resulting in dramatic declines in species diversity, and promoted the importance of deterministic processes in community assembly. Our findings provide new insights into bacterial communities’ responses to the intensified climate-driven and anthropogenic environmental changes in aquatic ecosystems.

中文翻译：

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内蒙古半干旱高原地区水生细菌多样性，群落组成和组装：盐度和营养水平的综合影响

由于近几十年来的气候变化和人类的密集活动，内生湖泊受到盐碱化和富营养化的威胁。但是，关于水生细菌群落对同时增加盐度和营养状态的反应的知识仍然很贫乏。为了解决这一知识鸿沟，我们从内蒙古半干旱高原的五个湖泊和六个河流中收集了40个地表水样品，并使用16S rRNA基因靶向扩增子序列研究了它们的细菌群落。我们发现，从中营养的淡水河生境到富营养的高咸水湖泊生境，细菌物种多样性显着降低；在解释这种多样性下降的过程中，盐度比营养状态更为重要。盐度是影响社区组成的最重要的环境因素，而增加的氮负荷在构造预测的功能组成中更为重要。在湖泊栖息地内，环境过滤对细菌群落组装的影响随着盐度的增加而增加。结果表明，盐分和养分的升高对水生细菌群落产生综合影响，导致物种多样性急剧下降，并促进了确定性过程在群落聚集中的重要性。我们的发现为细菌群落对水生生态系统中加剧的气候驱动和人为环境变化的反应提供了新的见解。环境过滤对细菌群落组装的影响随着盐度的增加而增加。结果表明，盐分和养分的升高对水生细菌群落产生综合影响，导致物种多样性急剧下降，并促进了确定性过程在群落聚集中的重要性。我们的发现为细菌群落对水生生态系统中加剧的气候驱动和人为环境变化的反应提供了新的见解。环境过滤对细菌群落组装的影响随着盐度的增加而增加。结果表明，盐分和养分的升高对水生细菌群落产生综合影响，导致物种多样性急剧下降，并促进了确定性过程在群落聚集中的重要性。我们的发现为细菌群落对水生生态系统中加剧的气候驱动和人为环境变化的反应提供了新的见解。