Diversity And Nitrogen Metabolism Characteristics Of Plastisphere In Mangrove Sediments Of The Beihai

Microplastic pollution is a pressing environmental issue in marine environments.In marine settings,larger plastic waste gradually degrades into microplastics smaller than 5 mm in size.These microplastics are rapidly colonized by microbial communities,collectively forming the "plastisphere," a microecosystem within the marine environment that exerts complex effects.The accumulation of plastic particles in mangrove root systems and sediments leads to increased pollutant accumulation and enhanced biological toxicity,thereby impacting the structure and functioning of mangrove ecosystems.This study investigated the surface biofilms formed on microplastic particles exposed in mangrove sediment environments through an in-situ burial exposure method.The main findings are as follows:(1)Microplastic particles develop distinct "plastisphere" microbial ecosystems on their surfaces,which differ significantly from the surrounding sediment.The type of microplastic is crucial in shaping the initial microbial community changes during biofilm formation.The impact of plastic type on interstitial community formation is significant within 30 days of exposure,but decreases after 60 days.(2)The microbial community composition on microplastic particles significantly differs from that in the surrounding sediment.Prolonged exposure results in the enrichment of microbial taxa with plastic degradation potential,such as Erythrobacter and Exiguobacterium,within the biofilms.Consequently,the presence of biofilms promotes the degradation of microplastic particles.This study utilized quantitative PCR to assess the characteristics of ammonia oxidation and denitrification processes in microplastic-associated microbial communities.The main findings are as follows:(1)Bacterial abundance on microplastic biofilms is two to three orders of magnitude higher than fungal abundance.(2)The abundance of ammonia oxidation-related genes on microplastic biofilms surpasses that in mangrove sediments,possibly due to the expanded oxygenexposed surface area provided by microplastic biofilms,facilitating the aggregation of aerobic ammonia-oxidizing microorganisms on plastic surfaces.The abundance of denitrification-related genes closely correlates with bacterial abundance on plastic surfaces,stabilizing as the bacterial community on the plastic biofilm reaches stability.This study provides theoretical support for evaluating the impact of microplastics on mangrove ecosystems and exploring the microbial resources within mangroves that possess plastic degradation potential.Further research is necessary to assess the longterm effects of microplastics on mangrove ecosystems.Long-term monitoring can be conducted to evaluate the accumulation and distribution of microplastics within mangrove habitats,facilitating the study and development of potential remediation strategies to alleviate the impact of microplastics on mangrove ecosystems.