Structure and assembly mechanisms of different microbial taxa in plastisphere in coastal wetlands: An in-situ culture experiment.

Microplastics (MPs), an emerging global pollutant, create a distinct "plastisphere" niche on their surfaces in coastal wetlands, yet its effects on microbial community structure and assembly remain poorly understood. Through in situ incubation, high-throughput sequencing, and ecological modeling, this study systematically revealed differences in microbial community structure, function, and assembly mechanisms between the plastisphere and surrounding sediment, and further examined the modulating roles of vegetation type (vegetated P site vs. bare I site) and polymer degradability (traditional: PP, PET; biodegradable: PLA, PBAT). Compared to the surrounding sediment, the plastisphere shifts microbial assembly from dispersal limitation (75.4-79.2%) dominated by physical isolation to co-dominated by homogeneous selection (12.5-44.2%, driven by MPs surface properties) and ecological drift (55.8-84.0%, intensified by MPs physicochemical properties). This shift provides an intrinsic ecological explanation for the observed structural simplification (diversity reduction, rare taxa loss) and functional specialization of plastisphere communities. Notably, the plastisphere also significantly altered the abundance of functional genes involved in carbon/nitrogen cycling, an effect particularly pronounced on biodegradable MPs. Network analysis indicated that plastisphere co-occurrence networks have fewer nodes, while microbial connectivity and cooperative interactions are significantly enhanced, reflecting microbial adaptive strategies to the new habitat. This restructuring of both community architecture and function suggests that MPs may change local biogeochemical cycling potential while increasing the risks of pathogen enrichment and uncertainty in community dynamics. Furthermore, vegetation presence partially mitigated the negative impact of MPs on bacterial diversity, primarily by altering the sediment background community. Our findings provide a scientific understanding for assessing the ecological impact of MPs in coastal ecosystems.