Niche vs. habitat: Insights of aging microplastics and wetland types on bacterial community assembly

Microorganisms can colonize the surface of microplastics (MPs) to form a distinctive microbiome, known as a "plastisphere" which is regarded as an anthropogenic niche for microbial growth. However, bacterial community assembly in virgin and aging MP plastispheres across different habitats is poorly understood. This study aims to assess the variations in bacterial community assembly across different niches and habitats with an in situ experiment, in which constructed forest wetland (FW), natural lake wetland (LW), and lotus pond wetland (LP) were habitats, and plastispheres of virgin and aging low-density polyethylene (LDPE) MPs, as well as surrounding wetland soils were niches. Significant niche-related differences in bacterial communities were observed, with lower diversity and enrichment of potential plastic-degrading bacteria in the plastisphere than in the soil bacterial communities. Furthermore, habitat-related differences exerted a more pronounced influence on the beta-diversity patterns of the bacterial communities. The linear regression analyses indicated that the local species pool contributed more to bacterial community assembly in the LW wetland, whereas the relative abundance of species was the primary factor in the LP wetland. The null model analysis indicated that plastisphere bacterial communities were predominantly driven by the stochastic process, with a more deterministic assembly observed in the LP wetland and soil bacterial communities. Additionally, the primary ecological process shaping plastisphere communities shifted from drift in the virgin LDPE to homogenising dispersal in the aging LDPE. This study provides new insights into the fate and ecological impacts of MPs in wetlands, thereby facilitating the effective regulations of plastic pollution.