Distribution and potential ecological risks of microplastics in Zhushan Bay, China

The interaction between microplastics (MPs) and microorganisms may alter the distribution of antibiotic resistance genes (ARGs) in water and increase the ecological risk of drinking water sources. To investigate the characteristics of MPs geographical distribution and its potential ecological risk in typical urban water, this study was conducted in Zhushan Bay, and we carried out a combination of tests to analyze the distribution of MPs and the migration changes of their surface microbial community composition and ARGs in different media by 16S rRNA gene high-throughput sequencing, non-targeted metabolomics and qPCR genomics in the near-shore (I), middle area (Ⅱ) and near-lake (Ⅲ) of Zhushan Bay. The results showed that MPs in fibrous form were dominant in the aquatic environment of Zhushan Bay; Polyurethane (PU) and Silicone were the main MPs types in Zhushan Bay. The abundance of MPs in the water of Zhushan Bay was winter > summer > autumn > spring; and in the sediment was winter > summer > autumn > spring, respectively. The distribution results of MPs in geographical location are as follows: In the water I > Ⅱ > Ⅲ, sediment exhibited Ⅱ > Ⅲ > I. The results indicate that physicochemical factors will affect the geographical distribution of MPs and their surface microbial community composition in the aquatic environment of Zhushan Bay. More cooperative behaviors and increased metabolically important pathways occurred in the microbial network on water-MPs compared to sediment-MPs. However, the microbial community in the sediment-MPs was more stable and had higher abundance of mobile genetic elements (MGEs). A total of 362 differential metabolites were detected, of which 193 were up-regulated and 19 down-regulated differential metabolites. blaTEM, Sul, and inti1 were prevalent in both the water and sediments of Zhushan Bay. Sul1 was most contaminated in ARGs. This study provides the latest field data and insights into MPs pollution in key aquatic environments.