Microbiomes of coastal sediments and plastispheres shaped by microplastics and decabrominated diphenyl ether

Deciphering the impact of microplastic and persistent organic pollutants (POPs) co-contamination on coastal sediment is critical for developing effective remediation strategies for polluted sites yet remains underexplored. This study investigated the interactions between microplastics, decabrominated diphenyl ether (deca-BDE), and their co-contamination effects on the evolvement of coastal sediment and plastisphere microbiomes for over 2 years. Results showed that deca-BDE was naturally debrominated in sediments via diverse pathways, with microplastic polystyrene stimulating the debromination rate by up to 78.7 ± 10.0 %. The putative OHRB Dehalobacter and uncultured Dehalococcoidia populations were identified responsible for the complete debromination. Co-exposure to microplastics and deca-BDE induced significant shifts in community composition, diversity, and function in the sediment microbiomes, while plastisphere microbiomes exhibited distinct compositions and functional profiles, specializing in pathogenicity, pollutant degradation, and biogeochemical cycling. The type of plastics and the presence of deca-BDE influenced the plastisphere composition. Changes in sediment properties and debromination activity profoundly shaped microbial communities, with deterministic assembly dominating the plastisphere. Co-contamination increased the complexity, modularity, and stability of the plastisphere networks, creating unique niches for OHRB. These findings highlight the intricate interplay between microplastics, deca-BDE, and microbiomes, with significant implications for ecosystem health and remediation efforts.