Aquifers, springs and other groundwater‐dependent ecosystems are threatened by urban land use, which causes water quality deterioration through nutrient loading, sewage infiltration, groundwater extraction and, along coasts, seawater intrusion. The presence of certain microbes in groundwater can indicate that an aquifer is anthropogenically contaminated. Interpretations made from observations of indicator microbes in groundwater are limited because the relationship between the presumably allochthonous indicator microbes and relevant autochthonous microbial communities has not been characterized. This study addressed whether autochthonous aquifer biofilms can influence the presence of presumed microbial indicators in groundwater, and simultaneously used microbial indicators to trace sources of urban contamination at a karst spring of conservation concern. These questions were approached using a 17‐month time series analysis of attached biofilm and adjacent unattached bacteria in the submerged karst aquifer conduit associated with this spring. Environmental 16S rRNA gene sequencing was performed to characterize these communities, and community structure data were contextualized with groundwater geochemical and hydrogeological measurements. Linear regression models were developed to explain the relative abundance patterns of indicator microbes and other unattached microbes at this site. The results of this study suggest that dominant aquifer biofilms do not influence the presence of unattached microbial taxa that are presumed to be indicators of groundwater contamination, and generated new information about the origin of coliform bacteria at the study site. These results build confidence in the use of microbial indicators in groundwater‐dependent ecosystem conservation strategies and inform future management plans for urban aquifers and springs worldwide.

中文翻译：

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含水层生物膜与城市地下水污染的独立微生物指标之间的关系

含水层，泉水和其他依赖于地下水的生态系统受到城市土地使用的威胁，这会通过营养负荷，污水渗透，地下水提取以及沿海岸带的海水入侵而导致水质恶化。地下水中某些微生物的存在可能表明蓄水层被人为污染。地下水中指示微生物的观察结果的解释是有限的，因为未表征异源指示微生物与相关的原生微生物群落之间的关系。这项研究探讨了土生土层生物膜是否会影响地下水中假定微生物指标的存在，同时使用微生物指标来追踪在保护方面引起的岩溶之春的城市污染源。这些问题是通过17个月的时间序列分析法来解决的，该分析法分析了与该春季相关的淹没的岩溶含水层导管中附着的生物膜和相邻的未附着细菌。进行了环境16S rRNA基因测序来表征这些群落，并利用地下水地球化学和水文地质测量对群落结构数据进行了背景分析。建立线性回归模型来解释指示微生物和其他未附着微生物在该位置的相对丰度模式。这项研究的结果表明，主要的含水层生物膜不会影响被认为是地下水污染指标的未附着微生物类群的存在，并在研究地点生成了有关大肠菌细菌起源的新信息。这些结果使人们对在依赖地下水的生态系统保护策略中使用微生物指标建立了信心，并为全球城市含水层和泉水的未来管理计划提供了依据。