Non-additive effects of microplastics, atrazine, and sulfamethoxazole co-exposure on Penaeus vannamei health and environmental risks

Microplastics (MPs), pesticides, and antibiotics frequently co-occur in aquatic environments, yet their combined toxicity-particularly that of charged, surface-modified MPs-remains poorly understood. Here, Penaeus vannamei was used as a model to investigate the combined toxicity of carboxylated polystyrene (PS-COOH), atrazine (ATZ), and sulfamethoxazole (SMX) at environmentally relevant concentrations. Compared with single exposures, ATZ and SMX accumulation decreased by 15.7% and 70.1% in binary groups and by 72.1% and 35.9% in the ternary group, respectively. Co-exposure, especially ternary exposure, alleviated hepatopancreatic injury but exacerbated declines in antioxidant capacity and detoxification function. Metabolomic profiling revealed more extensive disruptions under ternary exposure, with enrichment of pathways including pentose phosphate, neuroactive ligand-receptor interactions, and ABC transporters. Binary exposures produced more specific OTUs and altered taxa, whereas ternary exposure intensified community deviation, increased genus-level diversity, and balanced dominant and rare taxa. Microbiota-metabolite correlations linked binary exposure to nervous system, lipid metabolism, and immunity, whereas ternary exposure expanded these associations to cholesterol regulation, aromatic compound metabolism, and nitrogen/carbon cycling. Importantly, ternary exposure enhanced antibiotic resistance gene (ARG) diversity and generated novel ARG combinations, raising concerns for One Health. Collectively, this study addresses key gaps in multi-pollutant ecotoxicology and emphasizes the need for integrated risk assessment of compound pollution.