Comparison of freshwater microbial communities in water and microplastics surfaces: insights from Dongting Lake, China

In recent years, microplastics (MPs) in freshwater lake have been receiving increasing attention; however, the microbial communities on the surface of MPs have not been well studied. To investigate the potential risk posed by MPs to the lake ecosystem and its surface microbial community structure, MPs samples were collected in September 2023 in the freshwater Dongting Lake, Hunan, China, at five sites, and the differences in bacterial species community composition and structure between MPs and water samples were analyzed. Results show that MPs (13.71 +/- 3.32 items/L) in the samples were mostly black in color, fiber in shape, and PES in composition, and those <0.5 mm in size are dominant. The bacterial composition in water was different from that on MPs. At phylum level, Proteobacteria, Actinobacteria, Cyanobacteria, and Bacteroidetes were dominated in relative abundance in both water and MPs. Proteobacteria was more abundant in MPs than in water. The relative abundance of Bacteroidota and Actinobacteriota was significantly lower in MPs than in water. At genus level, Pantoea and Pseudomonas were potentially pathogenic genera in MPs surfaces. The presence of Cyanobacteria and pathogenic bacteria is undoubtedly a potential risk to the deterioration of the water quality. This study revealed the difference in the distribution of bacterial community in water and MPs in Dongting Lake and provided new perspectives to further understanding of MPs pollution in freshwater lakes.