Disturbance is known to affect the ecosystem structure, but predicting its outcomes remains elusive. Similarly, community diversity is believed to relate to ecosystem functions, yet the underlying mechanisms are poorly understood. Here, we tested the effect of disturbance on the structure, assembly, and ecosystem function of complex microbial communities within an engineered system. We carried out a microcosm experiment where activated sludge bioreactors operated in daily cycles were subjected to eight different frequency levels of augmentation with a toxic pollutant, from never (undisturbed) to every day (press-disturbed), for 35 days. Microbial communities were assessed by combining distance-based methods, general linear multivariate models, α-diversity indices, and null model analyses on metagenomics and 16S rRNA gene amplicon data. A stronger temporal decrease in α-diversity at the extreme, undisturbed and press-disturbed, ends of the disturbance range led to a hump-backed pattern, with the highest diversity found at intermediate levels of disturbance. Undisturbed and press-disturbed levels displayed the highest community and functional similarity across replicates, suggesting deterministic processes were dominating. The opposite was observed amongst intermediately disturbed levels, indicating stronger stochastic assembly mechanisms. Trade-offs were observed in the ecosystem function between organic carbon removal and both nitrification and biomass productivity, as well as between diversity and these functions. Hence, not every ecosystem function was favoured by higher community diversity. Our results show that the assessment of changes in diversity, along with the underlying stochastic-deterministic assembly processes, is essential to understanding the impact of disturbance in complex microbial communities.

中文翻译：

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干扰的频率会改变复杂细菌群落的多样性，功能和潜在的组装机制。

已知干扰会影响生态系统结构，但预测其结果仍然难以捉摸。同样，人们认为社区多样性与生态系统功能有关，但对潜在的机制知之甚少。在这里，我们测试了工程系统中扰动对复杂微生物群落的结构，组装和生态系统功能的影响。我们进行了一个微观实验，其中每天循环运行的活性污泥生物反应器在八种不同频率的频率下进行有毒污染物的增强，从没有（不受扰动）到每天（受压力扰动）持续35天。通过结合基于距离的方法，通用线性多元模型，α-多样性指数以及对宏基因组学和16S rRNA基因扩增子数据的无效模型分析，对微生物群落进行了评估。在扰动范围的极端，未受扰动和受压扰动的末端，α多样性在时间上的更强烈的下降导致了驼峰型模式，在扰动的中间水平发现了最高的多样性。不受干扰和受新闻干扰的级别显示出最高的社区和功能相似性重复之间，表明确定性过程是主导。在中间干扰水平中观察到相反的情况，表明较强的随机组装机制。在生态系统功能中，在去除有机碳与硝化作用和生物量生产率之间以及在多样性与这些功能之间都存在权衡。因此，并不是每个生态系统功能都受到更高的社区多样性的青睐。我们的结果表明，对多样性变化的评估，