Impact of mariculture-derived microplastics on bacterial biofilm formation and their potential threat to mariculture: A case in situ study on the Sungo Bay, China

Microplastics (MPs) pollution in the marine environment has attracted considerable global attention. However, the colonization of microorganisms on mariculture-derived MPs and their effects on mariculture remain poorly understood. In this study, the MPs (fishing nets, foams and floats) and a natural substrate, within size ranges (1–4 mm), were then incubated for 21 days in Sungo Bay (China), and the composition and diversity of bacterial communities attached on all substrates were investigated. Results showed that bacterial communities on MPs mainly originated from their surrounding seawater and sediment, with an average contribution on total MPs adherent population of 47.91% and 37.33%, respectively. Principle coordinate analysis showed that community similarity between MPs and surrounding seawater decreased with exposure time. In addition, lower average bacterial community diversity and higher relative abundances of bacteria from the genera Vibrio, Pseudoalteromonas and Alteromonas on MPs than those in their surrounding seawater and sediments indicated that MPs might enrich potential pathogens and bacteria related with carbohydrate metabolism. They are responsible for the significant differences in KEGG Orthology pathways (infectious disease and carbohydrate metabolism) between MPs and seawater. The KO pathway (Infectious Diseases) associated with MPs was also significantly higher than those with feathers in the nearshore area. MPs might be vectors for enrichment of potentially pathogenic Vibrio , and enhance the ecological risk of MPs to mariculture industry. • MPs promote the adhesion of resident bacterial communities in seawater and sediments. • MPs are prone to enrich bacteria belong to Vibrio , Pseudoalteromonas and Alteromonas. • Organic matter plays an important role in formation of bacterial communities on MPs. • Enrichment of potential pathogens on MPs implies higher infection risk to mariculture. Lower bacterial community diversity and higher relative abundances of bacteria from the genera Vibrio , Pseudoalteromonas and Alteromonas on MPs than those in surrounding seawater and sediments indicated the selectively enrichment of potential pathogens and bacteria related with carbohydrate metabolism on MPs.