In Situ Exposure Effects on Microplastic Aging and Biofilm Colonization in Mangrove Forest

Mangrove wetlands act as ecological buffers and important sinks for pollutants such as microplastics, yet their surface transformation processes remain unclear. This study examines changes in the surface composition of polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) through ten field experiments in mangrove environments. The study indicates that the oxidation, hydrolysis and damage degree of PE, PP and PET all show that the exposed area above the sediment has a greater change compared to the buried area within the sediment. Spatial variation is evident, with the most severe degradation occurring in muddy seawater areas, and material susceptibility following the order PP > PE > PET. In muddy zones, damage decreases along the gradient: seawater > mudflat > mangrove > nearshore. Microbial analysis reveals that Proteobacteria and Bacteroidetes dominate microplastic biofilms. Specific genera are associated with different degradation patterns among microplastic types: Ruegeria, Sulfitobacter, and Neptuniibacter are positively correlated with PET degradation; Sulfurovum and Desulfobacter are positively correlated with PP degradation; and no positive correlation is observed between Sulfurimonas and PE degradation. These findings highlight the combined roles of environmental conditions and microbial communities in microplastic aging, offering insights for pollution mitigation strategies in mangrove ecosystems.