Colonization characteristics and dynamic transition of archaea communities on polyethylene and polypropylene microplastics in the sediments of mangrove ecosystems

Microplastics are a growing concern in mangrove ecosystems; however, their effects on archaeal communities and related ecological processes remain unclear. We conducted in situ biofilm-enrichment experiments to investigate the ecological influence of polyethylene (PE) and polypropylene microplastics on archaeal communities in the sediments of mangrove ecosystems. The archaeal community present on microplastics was distinct from that of the surrounding sediments at an early stage but became increasingly similar over time. Bathyarchaeota, Thaumarchaeota, Euryarchaeota, and Asgardaeota were the most abundant phyla. Methanolobus, an archaeal biomarker, was enriched in PE biofilms, and significantly controlled by homogeneous selection in the plastisphere, indicating an increased potential risk of methane emission. The dominant archaeal assembly process in the sediments was deterministic (58.85%−70.47%), while that of the PE biofilm changed from stochastic to deterministic during the experiment. The network of PE plastispheres showed less complexity and competitive links, and higher modularity and stability than that of sediments. Functional prediction showed an increase in aerobic ammonia oxidation during the experiment, whereas methanogenesis and chemoheterotrophy were significantly higher in the plastisphere. This study provides novel insights into the impact of microplastic pollution on archaeal communities and their mediating ecological functions in mangrove ecosystems. Microplastics, the emerging contaminants in mangrove ecosystems, comprise a "blue carbon" ecosystem. Buried carbon in mangrove sediments may be released into the atmosphere through archaeal methanogenesis. Microplastics mediate biofilm formation and affect microbial metabolism. The composition of archaeal communities on microplastics and their potential ecological function in facilitating methane cycling remains to be elucidated. Using in situ experiments, the colonization characteristics and dynamic transition of archaeal communities present on the microplastics in mangrove sediments were investigated. This study sheds light on the impact of microplastic pollution on archaeal communities and their modulation of ecological functions in mangrove ecosystems.