Groundwater is a key resource for safe drinking water supply. Yet unconfined aquifers can be vulnerable to microbial contamination during extreme weather events that lead to surface runoff. The current study characterises the groundwater microbiome of a porous basaltic rock aquifer in South-West Iceland used for drinking water extraction and analyses the microbial community dynamics during surface runoff. The groundwater microbial community sampled from twelve wells across the extraction area contained over 745 prokaryotic genera and was phylogenetically similar between wells and most seasons, representing a diverse but homogenous ecosystem. The largest seasonal variation in the microbial community composition was detected during a period of concurrent snow melt and high precipitation leading to surface runoff. This period was characterised by an increased abundance of soil-associated taxa in the groundwater microbiome and specifically of taxa assigned to Aeromonas and Bacillus. A field experiment simulating high surface runoff around a groundwater well confirmed the increased abundance of surface soil microorganisms in the well water, indicating vulnerability of groundwater towards surface microbial intrusion during extreme weather events. As such events are likely to increase due to climate change, novel water management tools such as microbial community analysis could help ensure drinking water safety.

中文翻译：

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用作市政水库的多孔玄武岩含水层地下水微生物组中的微生物入侵和季节动态

地下水是安全饮用水供应的关键资源。然而，在导致地面径流的极端天气事件中，无限制的含水层可能容易受到微生物污染。当前的研究表征了冰岛西南部用于饮用水提取的多孔玄武岩含水层的地下水微生物组，并分析了地表径流过程中的微生物群落动态。从整个提取区域的12口井中抽取的地下水微生物群落包含745个原核生物属，并且在井与大多数季节之间的系统发育上相似，代表了一个多样但均一的生态系统。在同时融雪和高降水导致地表径流期间检测到微生物群落组成的最大季节性变化。气单胞菌和芽孢杆菌。现场实验模拟了地下水井周围的高地表径流，证实了井水中地表微生物的丰度增加，这表明在极端天气事件中地下水对地表微生物入侵的脆弱性。由于此类事件可能由于气候变化而增加，因此新型的水管理工具（例如微生物群落分析）可以帮助确保饮用水安全。