Effects of Different Microplastics on Antibiotic Resistance Genes and Bacterial Communities in Sediments from Four Major Sea Areas in China

Microplastics (MPs) can accumulate antibiotic resistance genes (ARGs) in seawater, but their effects on sediment resistomes and microbial communities across different marine sediments remain poorly understood. A 30-day incubation experiment using polyethylene (PE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) MPs and composite sediments from four marginal seas of China was conducted. PE exposure significantly increased nearly all the abundances of intI1, sul1, tetA, and blaTEM in all four sediment sources (Bohai, Yellow, East China, and South China Seas), whereas PET and PVC produced sediment-dependent responses. PE-associated biofilms may provide protective niches that favor bacterial growth and ARG enrichment, while PET and PVC may exert inhibitory effects in some sediments. MP exposure was also associated with shifts in bacterial community composition and alpha diversity. Co-occurrence analysis identified Alcanivorax, Methylophaga, and Brevirhabdus as potential hosts associated with all target genes, whereas Idiomarina showed potential associations with tetA and blaTEM. Overall, the results indicate that MP effects on sediment ARGs and bacterial communities depend on both polymer type and sediment characteristics. Because the experiment used a high MP loading and carbon supplementation, further studies at environmentally relevant concentrations are needed to evaluate the ecological implications.