Responses of Groundwater Bacterial Communities to Extreme Rainfall in the Western North China Plain Based on 16S rRNA Sequencing

Extreme rainfall events significantly affect groundwater systems by altering hydrogeological conditions and accelerating the migration of pollutants, exacerbating the ecological vulnerability of over-exploited areas. However, there is a lack of systematic research on the ecological response mechanisms of microbial communities under extreme rainfall. This study focuses on the over-exploited area in the western North China Plain. Based on 16S rRNA sequencing analysis of 49 groundwater samples collected from the typical alluvial–diluvial plain in the study area impacted by extreme precipitation induced by Typhoon Doksuri, we revealed the effects of rainfall on the taxonomic composition, assembly mechanisms, and environmental drivers of groundwater microbial communities. We found that extreme rainfall influenced the distribution of dominant genera in groundwater and enriched tolerant bacterial communities, further causing a decline in groundwater microbial diversity. Our study confirmed that abundant subcommunities displayed strong microbial collaborations, while rare subcommunities exhibited higher sensitivity and evolved toward opportunistic groups after extreme rainfall. Rainfall influenced the composition of rare taxa, while enhancing the influence of stochastic processes to the assembly of subcommunities. Functionally, confined water favored anaerobic carbon fixation, methanogenesis and dissimilatory sulfate reduction, whereas the Calvin–Benson–Bassham pathway, nitrification, and denitrification were enriched in phreatic water. Additionally, abundant taxa exhibited significantly responses to carbon nutrients in shallow groundwater, whereas rare taxa were governed by mineral ions in deep confined aquifers after rainfall. This study expanded our knowledge of the groundwater microbiome driven by extreme rainfall events and was of great significance to the assessment of ecological stability in the western North China Plain.