The plastisphere ecology: Assessing the impact of different pollution sources on microbial community composition, function and assembly in aquatic ecosystems

In aquatic ecosystems microplastics (MPs) provide new habitat for microbes, forming the plastisphere. While, the effect of different pollution sources on microbiome compositions, functions and assembly processes remains largely cryptic, and hence requires further investigation. Thus, in this study microplastic and surrounding water samples were collected from four different locations and performed meta-analysis to evaluate the impact of different pollution sources on microbial community composition, function and assembly in plastisphere and surrounding environment. Results demonstrated that pollution source had a significant effect on microbial diversity (p = 0.0012) and composition (PERMANOVA F = 16.386; R² = 0.15, p < 0.001) in surface water and plastisphere. Specifically, plastisphere harboured distinct microbial community and recruited unique taxa compared to surface water, suggesting that microplastics serve as new ecological habitats. We observed a clear shift in microbial community composition, with Bacteroidetes being significantly higher in surface water significantly, whereas α- and β-Proteobacteria dominated the plastic surface (p < 0.05). These change in microbial communities were more likely due to unique chemical properties and substrates enrichment on plastic surfaces and different pollution sources. Genes involved in metabolism, signaling, cell motility, vesicular transport energy production and defence were significantly enriched in plastisphere (p = 0.001). The environmental factors such as DO and salinity drive the microbial communities in plastisphere. Niche-based selection process govern assembly in plastisphere microbiome, while as stochastic processes dominated the assembly process in aquatic microbial communities. These finding suggest that trajectory, continued microplastic emission and transport in aquatic ecosystems could pose serious planetary and health issues.