Distribution And Interaction Of Microplastics And Antibiotic Resistance Genes In Mariculture Areas Of Sansha Bay

As emerging contaminants,microplastics(MPs)and antibiotic resistance genes(ARGs)have been detected frequently in marine environment,especially in coastal mariculture areas.MPs can not only adsorb heavy metals,PAHs,antibiotics and other contaminants in water,but may be a great habitat carrier for microbial community and promote the formation of biofilms.Under the pressure of low-concentration residual antibiotics,MPs promote the reproduction of antibiotic resistant bacteria(ARB)and the exchange and expression of ARGs,causing risks to mariculture environment and health of cultured animals.Unfortunately,relevant studies have only been focused on the distribution characteristics of MPs or ARGs in marine environment,while limited attention has been paied to the combined ecological effects by the both contaminants,and their influences on the development of mariculture.Therefore,we chose Sansha Bay,a typical mariculture semi-closed-coastal bay in the southeast of China,as the research area to explore the occurrence,distribution,and correlation of MPs and ARGs in water and sediment.In addition,self-made MPs samples were submerged in the water of fish-culture areas for 6 weeks to simulate the enrichment of ARGs.At the same time,we changed the sizes,shapes and materials of MPs to explore the differences in the enrichment of ARGs.This paper aims to confirm the enrichment and diffusion of ARGs by MPs and related influencing factors in costal mariculture areas.The followings are the main findings:(1)MPs were widely detected at 12 water samples and 8 sediment samples in Sansha Bay,and polypropylene(PP),polyethylene(PE),polyamide(PA)and rayon(RA)were the dominat types.The abundance of MPs(>50 μm)in water ranged from 22.5±3.5 items/L to 59.3±8.2 items/L,and the corresponding in sediment ranged from 365.5±36.9 items/kg to 1970.3±137.8 items/kg.The abundances of MPs in the fish culture area(S4～S11)were much higher than those in the seaweed culture area(S1～S3)and Dongchong channel(S12).Fibers were the most common type of MPs in both water and sediment.The colors of MPs in the water were mainly transparent and blue,while in sediment were mainly black(gray)and white.MPs with particle size range of 100500 μm had the highest proportion(33.21%～46.76%).(2)11 ARGs and intIl were detected completely in water and sediment,and there were significant regional differences in the abundances distribution under the influence of mariculture activities.The seaweed culture areas were detecded the highest absolute abundances of ARGs while the fish culture areas were detected the highest relative abundances of ARGs.The fish culture areas may be under a greater risk of ARGs horizontal gene transfer(HGT).The abundances of ARGs in winter were higher than those in summer,and sul and tet were the dominant ARGs genotypes in both water and sediment.The abundances of MPs,ARGs and intIl had positively correlationships in water,indicating that intIl may play an important role in the HGT of ARGs,and MPs as the carrier promoted the spread of ARGs in water.(3)Through the MPs field exposure experiment,MPs increased the diversity of microbial community in water.The abundances of main hosts of ARGs(such as Bacteroidetes,Actinobacteria and Firmicutes)on the surface of MPs were significantly higher than in water.The types and abundances of ARGs on the surface of MPs were inferior to those in sediment but were superior to those in water.MPs increased significantly the types and abundances of multidrugs ARGs in water.The enrichment degrees of ARGs on surface of MPs were positively correlated with the abundances of intll,which indicated that the HGT played an important role in the process of ARGs enrichment by MPs.(4)The enrichment degree of ARGs was independent to the materials of MPs,but significantly affected by shapes and sizes of MPs.The granulars had better enrichment ability than fibers,and small particles(200～500 μm)had more excellent enrichment affect than the large particles(1～3 mm).This study was conducive to further understand the mechanism by which MPs can be an effective carrier of ARGs,and accelerate the enrichment,migration and diffusion of ARGs.The paper may provide updated insights and theoretical data support for better evaluation of the ecological effects and potential ecological risks of MPs and ARGs combined pollution in coastal mariculture environment.