Antibiotic resistance genes across divergent wetland types: Profiles, driving mechanisms, and risk assessment.

Wetlands are critical reservoirs and hotspots of antibiotic resistance genes (ARGs). Metagenomic sequencing was employed to profile the ARG and mobile genetic element (MGE) abundance and diversity in coastal (B), constructed (R), and swampy (W) wetlands. In total, 560 ARGs were detected across all sites, primarily conferring resistance to cephalosporins and tetracyclines, with antibiotic efflux being the dominant mechanism of resistance. ARG richness was significantly higher in wetlands R and W than in wetland B (p < 0.001). Non-metric multidimensional scaling (NMDS) further indicated significant differences in ARG β-diversity among the wetlands. Pseudomonadota were identified as the primary hosts of both ARGs and MGEs. Soil salinity and Cr content were the key environmental factors regulating ARG profiles, with salinity exhibiting the broadest influence and linearly correlating with multiple ARG types. In addition, plasmid and insertion sequence (IS) richness positively correlated with ARG richness, showing the strongest explanatory power for ARG richness variation. Risk assessment revealed that rank I and II ARGs were significantly enriched in wetland W (p < 0.05), whereas rank IV ARGs were dominant across most sites. This study demonstrated that soil physicochemical properties, plasmids, and ISs jointly and differentially shaped ARG abundance and diversity in wetlands, accompanied by an assessment of their risk. These findings support the development of targeted strategies to mitigate ARG dissemination in wetland ecosystems.