Combined Toxicites Of Microplastics And Sulfonamide On The Inestinal Microorganisms And Reproduciton In Marine Medaka

Microplastics pollution in the marine environment has become one of the critical concerns worldwide.Microplastics with small size,higher specific surface area and strong hydrophobicity can absorb toxic and harmful compounds,such as heavy metals,antibiotics,and persistent organic pollutants in the environment.Sulfanilamide is a kind of antibiotics with strong toxicity and relatively high environmental enrichment,and is also one of the most popular antibiotics in coastal environments in China,especially in coastal aquaculture area.Although microplastic combined with antibiotic pollution are ubiquitous in aquaculture area,the information on coupled and harmful effects of microplastic and antibiotic pollution on ecosystem is limited.Marine medaka(Oryzias melastigma),a desired type of marine model species,has been widely used in marine ecotoxicology research in recent years.But until recently,few studies are related to the synergy between microplastics and antibiotics.It is still unknown whether the microplastic-antibiotic adsorption process increases the exposure risk of antibiotic to marine life.In present study,sulfamethazine(SM₂)and polystyrene(PS)were selected as the representative compounds for sulfonamide antibiotic and microplastic,respectively to determine the individual effect of PS or SM₂ and their combined effects on intestinal microbial flora,intestinal health and growth and reproduction of marine medaka in the form of food-phase exposure.The major conclusions are as follows:1)After exposure to SM₂with environmental concentrations for 30 days,the abundance and diversity of intestinal microbes and the structural composition of intestinal flora at the phyla and genus levels in marine medaka have changed significantly.Those influences showed no significantly differences between female and male marine medaka,but the oxidative stress response of the intestine showed a certain gender difference.It is that SM₂ could significantly induce oxidative stress response in the intestinal tract of female fishes,while no significant change was observed in males.2)After exposure to SM₂ with environmental concentration for 30 days,the results showed that SM₂ had no significant effect on the growth of marine medaka,due to the fact that there was no significant change in the body length and weight of both female and male fishes.However,it significantly reduced the gonadal index of male fish and the expression of cy19a gene in the testis,and caused certain negative effects on the development of male testis and the balance of sex hormones.3)The individual exposure of PS did not significantly affect the diversity and abundance of intestinal microbes,growth and reproduction of marine medaka,and also did not cause oxidative damage to the intestinal tract of female and male fishs.4)When PS is present,the effects of SM₂ on the intestinal microbial community structure and oxidative stress of Marine medaka tended to be alleviated,and the reproductive toxicity of SM₂ also tended to decrease,indicating that the presence of microplastic may alleviate the toxic effects of SM₂ and reduce the potential ecological risks of SM₂.The above results indicate that sulfanilamide antibiotic contamination in the environment may induce dysregulation of intestinal flora in Marine fish and have some negative effects on reproductive health.However,when microplastics and antibiotics exist at the same time,microplastics may have a moderating effect on the toxicity of antibiotics,and its mechanism needs to be further studied and discussed.This study will provide a new direction for the treatment of diseases related to the dysregulation of intestinal flora and the development of new drugs,as well as a scientific basis for the screening and transformation of specific intestinal flora.At the same time,it provides scientific reference and support for the scientific assessment of ecological risks caused by microplastics and antibiotics in Marine environment.