Impacts of sulfamethoxazole on natural periphyton physiology and microbial community stability: Implications for aquatic ecosystem resilience

Periphyton, a critical microbial consortium regulating energy flow and nutrient cycling in aquatic ecosystems, plays a pivotal role in shaping biogeochemical processes and biodiversity indicator. However, the structural and functional responses of natural periphyton to high-concentration sulfamethoxazole remain poorly unclear. Here, we investigated the multilevel impacts of sulfamethoxazole (SMX) on periphyton through integrated high-throughput sequencing, physiological functions, and nutrient utilization analysis. Our results suggested that SMX exposure induced concentration-dependent ecological potential impairment. High concentrations (25-100 mg/L) significantly elevated dissolved organic carbon levels (105.92-239.78% increase) in water, while low SMX (5 mg/L) suppressed photosynthetic pigments, extracellular polymeric substances, and triggered malondialdehyde increase. Microbial diversity underwent drastic restructuring, with eukaryotic richness declining by 18.70-21.77%. The microbial community restructuring was characterized by stress-tolerant genera, including Edaphobaculum, Flavobacterium, Kouleothrix, Tobrilidae and Stylonychia. Sensitive genera to SMX exposure showed significant reductions, including Pirellula, Rhodobacter, Scenedesmus and Acutodesmus. Co-occurrence network analysis indicated SMX-driven topological erosion (22.37-41.44% reduced connectivity at 25 and 100 mg/L) destabilized microbial interactions. Periphyton retained nitrogen and phosphorus utilization capacity, with several resistant taxa (Pseudomonadota, Chloroflexota, Ciliophora) partially potential maintaining nutrient assimilation functions despite SMX stress. This study suggests periphyton under antibiotic stress may function as both a selector for antibiotic-tolerant taxa and a contributor to potential bioremediation applications. Our findings advance the development of natural periphyton ecological resilience strategies to mitigate antibiotic polluted wastewater.