Environmental drivers impact the accumulation and diversity of antibiotic resistance in green stormwater infrastructure

Antibiotic resistance poses an urgent public health concern, with the environment playing a crucial role in the development and dissemination of resistant bacteria. There is a growing body of research indicating that stormwater is a significant source and transport vector of resistance elements. This research sought to characterize the role of green stormwater infrastructure (GSI), designed for stormwater infiltration, in accumulating and propagating antibiotic resistance in the urban water cycle. Sampling included 24 full-scale GSI systems representing three distinct types of GSI - bioswales, bioretention cells, and constructed wetlands. The results indicated that GSI soils accumulate antibiotic resistance genes (ARGs) at elevated concentrations compared to nonengineered soils. Bioretention cells specifically harbored higher abundances of ARGs, suggesting that the type of GSI influences ARG accumulation. Interestingly, ARG diversity in GSI soils was not impacted by the type of GSI design or the diversity of the microbial community and mobile genetic elements. Instead, environmental factors (catchment imperviousness, metals, nutrients, and salts) were identified as significant drivers of ARG diversity. These findings highlight how environmental selective pressures in GSI promote ARG persistence and proliferation independently of the microbial community. Therefore, GSI system have the potential to be a substantial contributor of abundant and diverse ARGs to the urban water cycle. Green Stormwater Infrastructure (GSI) soils are environmentally relevant because of their potential role as reservoirs for hazardous materials, specifically antibiotic resistance genes (ARGs). In this research, GSI sites were identified as hotspots for ARG sequestration. Moreover, the diversity in antibiotic resistomes was influenced by environmental parameters including heavy metal, nutrients, and salt concentrations. The accumulation of ARGs in GSI soils raises concerns about the environmental dissemination and proliferation of antibiotic resistance throughout the urban water cycle. Understanding ARG dynamics in GSI is crucial for informing design decisions to leverage GSI as a tool to mitigate the spread of antibiotic resistance.