Meta-analysis reveals significant microbial community differentiation between plastisphere and surrounding water in aquatic environments

Aquatic microplastics harbor a unique biofilm termed the plastisphere. However, study-level quantitative synthesis of paired plastisphere–surrounding water differences in microbial diversity, community composition, and immigration-related assembly parameters remains limited. We performed a meta-analysis of 15 16S rRNA gene sequencing studies (1091 samples) comparing plastisphere and surrounding water microbiomes. Community α-diversity indices showed a non-significant tendency to be higher in the plastisphere than in the surrounding water. Importantly, β-diversity analysis revealed consistent and significant differentiation between habitat types, with habitat type explaining a moderate but statistically significant proportion of compositional variance. Taxonomic analysis identified enriched taxa dominated by Proteobacteria, along with depleted genera primarily affiliated with Actinobacteria and Bacteroidetes. A random forest classifier distinguished the two habitats with excellent performance (accuracy: 96%). Neutral community modeling revealed that the immigration rate (m) was significantly lower in the plastisphere (pooled lnRR = −1.39, 95% CI: −2.09 to −0.70), indicating reduced dispersal from the regional pool. These findings do not support a universal reduction in microbial α-diversity on microplastic surfaces and instead indicate that α-diversity responses are strongly context dependent, where estimated reduction in immigration and lower stochasticity may contribute to distinct and variable microbial assemblages. This study highlights the necessity of accounting for contextual drivers and assembly mechanisms in assessing ecological impacts of microplastic pollution.