Bacterial communities on microplastics in a wetland ecosystem

Microplastics (MPs), a new type of environmental pollutant, can serve as substrates for microbes. Wetland ecosystems support a diverse range of aquatic and terrestrial species, and their ecological functions can be disturbed by inputs of microplastic debris. However, limited studies have focused on the interactions between MPs and microbes in wetland ecosystems. In this study, the bacterial communities on MPs in the wetland ecosystem of Poyang Lake, China’s largest freshwater lake, were investigated based on 16S rRNA sequencing. We found that the bacterial communities on MPs showed a lower richness and diversity but presented a higher number of unique OTUs than the water and sediment bacterial communities. Furthermore, the structure of the bacterial communities on MPs had a higher similarity to the bacterial compositions of the sediment than of the water, indicating that sediments are an important source of bacteria for MPs. It should be noted that the MPs could enhance the exchange of bacteria between water and sediment. The bacterial composition varied significantly among different substrates and at different sampling times; nevertheless, it showed consistency on the surface of MPs at different sampling sites. Proteobacteria dominated as the most abundant bacterial phylum across all samples. At the genus level, Pseudomonas were distinctly enriched in bacterial communities on MPs. In addition, the results of pathway prediction indicated that the pathways of “human disease” from MPs bacterial communities were higher than those from water and sediment. These results illustrate that the surfaces of MPs serve as distinct habitats for specific bacteria. Environmental factors such as nitrate nitrogen, pH, and organic matter were crucial in shaping the bacterial communities. This study provided a new insight into interactions between MPs and microbes in wetland ecosystems and into the associated potential risks to human health.