The response of microbial communities to releases of hydraulic fracturing flowback and produced water (PW) may influence ecosystem functions. However, knowledge of the effects of PW spills on freshwater microbiota is limited. Here, we conducted two separate experiments: 16S rRNA gene sequencing combined with random forests modelling was used to assess freshwater community changes in simulated PW spills by volume from 0.05% to 50%. In a separate experiment, live/dead cell viability in a freshwater community was tested during exposure to 10% PW by volume. Three distinct patterns of microbial community shifts were identified: (i) indigenous freshwater genera remained dominant in <2.5% PW, (ii) from 2.5% to 5% PW, potential PW organic degraders such as Pseudomonas, Rheinheimera and Brevundimonas became dominant, and (iii) no significant change in the relative abundance of taxa was observed in >5% PW. Microbial taxa including less abundant genera such as Cellvibrio were potential bioindicators for the degree of contamination with PW. Additionally, live cells were quickly damaged by adding 10% PW, but cell counts recovered in the following days. Our study shows that the responses of freshwater microbiota vary by spill size, and these responses show promise as effective fingerprints for PW spills in aquatic environments.

中文翻译：

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水生微生物群落的响应和水力压裂返排和采出水的生物指标建模。

微生物群落对水力压裂回流和产出水（PW）释放的响应可能会影响生态系统功能。但是，有关PW溢出对淡水微生物群影响的知识是有限的。在这里，我们进行了两个单独的实验：16S rRNA基因测序与随机森林建模相结合，用于评估模拟的PW溢出物中淡水群落的变化，其变化量为0.05％至50％。在一个单独的实验中，在暴露于体积百分比为10％的PW期间，测试了淡水群落中活/死细胞的生存能力。确定了三种不同的微生物群落转移模式：（i）土著淡水属在PW低于2.5％时仍占主导地位；（ii）从2.5％到5％PW占主导地位，潜在的PW有机降解物（如假单胞菌，莱茵海默氏菌和Brevundimonas）成为优势菌，（iii）在> 5％的PW中，未观察到分类单元的相对丰度的显着变化。包括较不丰富的属（如Cellvibrio）在内的微生物分类群是造成PW污染程度的潜在生物指标。此外，添加10％PW会迅速破坏活细胞，但随后几天细胞计数恢复。我们的研究表明，淡水微生物群的响应随溢流大小而变化，这些响应显示出有望作为水生环境中PW溢流的有效指纹。