Microplastic-associated Bacterial Assemblages In Some Coastal Areas Of Southeast China

Plastic marine debris is a common pollution in the ocean.In the marine environment,large plastic debris will not only gradually decompose into microplastics with the size of smaller than 5 mm,but also cause harms to the marine environment.Meanswhile,these microplastics will be rapidly occupied by the microorganisms in the ocean and together constitute a "Plastisphere" micro-ecology,which will have more complex impacts on the marine environment.However,the knowledge of the plasticassociated microbial community(the plastisphere)in the intertidal zone is scanty.Microorganisms on marine microplastics and the choice of plastic polymer types for microbial communities are not yet clear in the “Plastisphere”.Therefore the “Plastisphere” formed by microplastics and attached microorganisms in the marine environment needs urgent research.Terrestrial and marine ecosystem interactions occur in the intertidal zone where accumulation of plastic frequently occurs.The aquaculture area can directly produces marine plastic debris,and closely related to the hygiene of human aquatic products.In this study,we used a high throughput sequencing approach to compare marine microplastic-associated bacterial assemblages in different regions around the Yangtze River estuary and adjacent ocean,and to study the marine microplastic-associated bacterial assemblages seasonal variation in different aquaculture regions of the southeast coastal areas.These findings illustrate diversity microbial assemblages that occur on microplastic and increase our understanding of plastisphere ecology.The main research contents and results are as follows.The biodiversity,composition categories,potential pathogens,key bacterial groups and metabolic pathways of the microplastic-associated bacterial assemblages in the intertidal zone of the Yangtze River estuary and adjacent sea areas were studied.This study found that 1.The composition and structure of the microplastic-associated bacterial assemblages in this study have significant differences in different regions.The composition of bacteria communities related to the sediment environment and water environment closely in where the microplastics located,and a small number of potential pathogens were found.2.Using network analysis method to screen the bacteria attached to the microplastics,predicted a keystone bacteria communities in the "Plastisphere"(eg:Rhodobacterales,Sphingomonadales and Rhizobiales),Other species(i.e.potential pathogens)were considered as hitchhikers in the plastic attached microbial communities.Metabolic pathway analysis suggested adaptations of these bacterial assemblages to the plastic surface-colonization lifestyle.These adaptations included reduced “cell motility” and greater “xeno-biotics biodegradation and metabolism.” The findings illustrate the diverse microbial assemblages that occur on microplastic and increase our understanding of plastisphere ecology.In order to define the distribution of the potential pathogens carried by marine microplastics in the aquaculture seawater,and the differences of bacteria communities attached to the microplastics in different seasons and regions,reveal the potential risks of “Plastisphere” to the marine environment and the health of aquatic products.The microplastic-associated bacterial assemblages in the aquaculture seawater were studied in the winter and summer.This study found that 1.In this study area,there are multiple potential pathogens in microplastics samples and seawater samples,and the abundance of some species are higher(such as Vibrio and Pseudomonas),and in one of the microplastic samples,the content of Vibrio reached 41.03%.At the same time,in this study,we found that the undetected potential pathogenic bacteria in seawater samples were found in Marine microplastic samples.2.The abundance of potential pathogens on the surface of microplastics was significantly higher in summer than the abundance of potential pathogens in winter.The microplastic-associated bacterial assemblages and the bacterial communities in surrounding water have a certain correlation in composition,but the biodiversity has significant difference between them.Meanswhile,the compositional structure of microplastic-associated bacterial assemblages have regional differences.There is no significant correlation between the plastic polymer type and the microplastic attached bacterial community.3.The analysis of the correlation between environmental factors and predominant bacteria attached to microplastics through heatmap explains the reasons for the differences of predominant bacteria in microplastic-associated bacterial assemblages under different seasons and regions.4.By using the method of network analysis,we screened the bacterial communities attached to microplastics and predicted a keystone bacterial communities in the "Plastisphere"(eg,Rhodobacteraceae,Actinobacteria,Cyanobacteria,Marinobacter).The study shows that in the aquaculture sea area of southeastern China,the potential pathogens in the microplastic-associated bacterial assemblages are widespread.In the summer,the abundance of microplastic pathogenic bacteria is higher.At the same time,marine microplastics can used as a medium for the transmission of pathogenic bacteria,which has potentially harmful to the marine environment and the safe of aquatic products.The composition and structural characteristics of the microplastic-associated bacterial assemblages related to the water environment,season,and geographic location,and have little correlation with plastic polymer types.