Freshwater ecosystems face many simultaneous pressures due to human activities. Consequently, there has been a rapid loss of freshwater biodiversity and an increase in biomonitoring programs. Our study assessed the potential of benthic stream bacterial communities as indicators of multiple‐stressor impacts associated with urbanization and agricultural intensification. We conducted a fully crossed four‐factor experiment in 64 flow‐through mesocosms fed by a pristine montane stream (21 d of colonization, 21 d of manipulations) and investigated the effects of nutrient enrichment, flow‐velocity reduction and added fine sediment after 2 and 3 weeks of stressor exposure. We used high‐throughput sequencing and metabarcoding techniques (16S rRNA genes), as well as curated biological databases (METAGENassit, MetaCyc), to identify changes in bacterial relative abundances and predicted metabolic functional profile. Sediment addition and flow‐velocity reduction were the most pervasive stressors. They both increased α‐diversity and had strong taxon‐specific effects on community composition and predicted functions. Sediment and flow velocity also interacted frequently, with 88% of all bacterial response variables showing two‐way interactions and 33% showing three‐way interactions including nutrient enrichment. Changes in relative abundances of common taxa were associated with shifts in dominant predicted functions, which can be extrapolated to underlaying stream‐wide mechanisms such as carbon use and bacterial energy production pathways. Observed changes were largely stable over time and occurred after just 2 weeks of exposure, demonstrating that bacterial communities can be well‐suited for early detection of multiple stressors. Overall, added sediment and reduced flow velocity impacted both bacterial community structure and predicted function more than nutrient enrichment. In future research and stream management, a holistic approach to studying multiple‐stressor impacts should include multiple trophic levels with their functional responses, to enhance our mechanistic understanding of complex stressor effects and promote establishment of more efficient biomonitoring programs.

中文翻译：

---

细小沉积物和流速对细菌群落和功能谱的影响大于营养物富集。

由于人类活动，淡水生态系统同时面临许多压力。因此，淡水生物多样性迅速丧失，生物监测计划增加。我们的研究评估了底流细菌群落作为与城市化和农业集约化相关的多重压力影响指标的潜力。我们对纯净的山ane水喂养的64个流过的中观膜进行了完全交叉的四因素实验（定居21 d，处理21 d），并研究了养分富集，流速降低和添加2次后细颗粒沉积物的影响。和3周的压力暴露。我们使用了高通量测序和元条形码技术（16S rRNA基因），以及精选的生物学数据库（METAGENassit，MetaCyc），以确定细菌相对丰度的变化和预测的代谢功能谱。沉积物增加和流速降低是最普遍的压力源。它们既增加了α多样性，又对社区组成和预测功能产生了特定的分类单元影响。沉积物和流速也经常相互作用，所有细菌反应变量中有88％显示双向相互作用，而33％显示包括养分富集的双向相互作用。常见分类单元的相对丰度变化与主要预测功能的变化有关，这可以推断为基础的全流机制，例如碳利用和细菌能量产生途径。随着时间的推移，观察到的变化基本上是稳定的，并且仅在暴露2周后发生，表明细菌群落非常适合早期发现多种应激源。总体而言，增加的沉积物和降低的流速不仅影响营养丰富，而且影响细菌群落结构和预测功能。在未来的研究和流管理中，研究多重压力影响的整体方法应包括多个营养级别及其功能响应，以增强我们对复杂压力影响的机械理解，并促进建立更有效的生物监测程序。