Dispersal, Establishment, and Functional Shifts of Runoff-Derived Bacterial Taxa Shaping Microbial Diversity in Infiltration-Based Aquifer Recharge Systems

Stormwater infiltration systems (SIS) are increasingly implemented to mitigate urban flooding and recharge groundwater but can disseminate chemical and biological contaminants, including pathogens. This study assessed the impact of six SIS, differing in vadose zone thickness and runoff transit time, on the microbial composition of the underlying aquifer. Groundwater samples and biofilms collected using passive samplers composed of 8 mm clay beads enclosed in inert pouches were analyzed via a tpm metabarcoding, enabling DNA read allocations at the species level. SIS altered groundwater tpm microbial diversity and community structure, especially in systems with shallow vadose zones and fast transit times. Downstream SIS groundwaters showed higher richness and colonization by potential pathogens such as species from Aeromonas, Pseudomonas, Stenotrophomonas, and Xanthomonas. Biofilms revealed more persistent and pronounced microbial changes than water samples, capturing bacteria with substrate-colonizing capabilities, such as Pseudomonas aeruginosa. Functional predictions from taxonomic allocations indicated a shift toward pollutant degradation and pathogenic traits in fast-transit systems. These findings indicate that SIS can promote waterborne pathogen establishment, threatening groundwater quality and public health. Transit time emerged as a critical factor modulating microbial impacts from tpm-harboring bacteria, underscoring the need to integrate microbial risk assessments into SIS design and management strategies.雨水渗透系统（Stormwater infiltration systems, SIS）正日益被用于缓解城市内涝并补给地下水，但同时也可能传播包括病原菌在内的化学与生物污染物。本研究评估了6个在包气带厚度与径流停留时间上存在差异的SIS，对下伏含水层微生物群落组成的影响。研究采用由封装于惰性袋中的8mm黏土珠构成的被动采样器采集地下水样本与生物膜，并通过tpm元条形码测序（tpm metabarcoding）进行分析，实现了物种水平的DNA读段分配。结果显示，SIS会改变地下水的tpm微生物多样性与群落结构，尤其是在包气带较浅、径流停留时间较快的系统中。下游受SIS影响的地下水呈现出更高的物种丰富度，且存在气单胞菌属（Aeromonas）、假单胞菌属（Pseudomonas）、寡养单胞菌属（Stenotrophomonas）与黄单胞菌属（Xanthomonas）等潜在病原菌的定殖。相较于水样，生物膜展现出更持久且显著的微生物变化，可捕获具备底物定殖能力的细菌，例如铜绿假单胞菌（Pseudomonas aeruginosa）。基于分类学分配的功能预测表明，在快速停留系统中，微生物群落向污染物降解与致病性状方向转变。本研究结果表明，SIS可促进水源性病原菌的定殖，威胁地下水水质与公众健康。径流停留时间作为调控携带tpm的细菌所产生的微生物影响的关键因素，凸显了将微生物风险评估纳入SIS设计与管理策略的必要性。