Ecotoxicological Study Of Carbamazepine And Microplastics In Aquatic Environment

In recent years,the occurrence of emerging pollutants in the aquatic environment has been widely reported,and its potential toxic effects on aquatic organisms have become the focus of current research.Due to the lack of environmental regulation,some of these pollutants are defined as emerging environmental pollutants with unmonitored concentrations in environments and unknown effects on human health and the environment.Carbamazepine and microplastics,as typical emerging pollutants,are difficult to be degraded in the environment and the environmental detection concentration keeps increasing.The study of their ecological effects is of great significance for the accurate assessment of their environmental risks.This study focused on the ecological toxicity and toxicological mechanisms of microplastics and pharmaceutical pollutants on biofilms as well as small fish zebrafish in aquatic environments.Irregular sizes of three types of typical microplastic(high density polyethylene,polyethylene terephthalate,and polystyrene)particles commonly found in the environment were prepared,and environmental river water samples for aquatic environmental exposure indoors were collected in order to investigate the interactions between these microplastics and the microbial communities in the aquatic environment.The attachment and growth of microorganisms on the surface of microplastics and the influence of microplastics on the microbial community structure in biofilms at different sampling sites in the upper and lower reaches of the river were studied using the Oxford Nanopore DNA sequencing technology.The differences of microbial communities in these biofilms and the correlation between microplastics properties and environmental samples were explored.In addition,the toxic effects and mechanisms of regular spherical 1-micron polystyrene fluorescently labeled microplastics on the growth,development,physiological reproduction and other representative key indicators of the aquatic model organism zebrafish(from embryo to larval fish and adult fish)were studied through carrying out chronic long-term exposure experiments.The effects of microplastic on zebrafish external fertilization as well as its transgenerational toxicity effects on adult zebrafish were revealed in addition.Through embryonic acute exposure,the effects of carbamazepine and microplastics on the growth,development and behavior of zebrafish embryos and larvae were compared and the mechanisms of the toxicities were studied.The study of microbial biofilms showed that microplastics at environmentally relevant concentrations had no significant effects on the structure of bacterial communities found in riverine waters,but the bacterial community structure on different types of microplastics was significantly different due to the difference in microplastic material hydrophobicity and hardness.The bacterial community structure of microplastic biofilms was strongly influenced by the aquatic environment of the river under the specific exposure conditions.The bacterial community structure of microplastic biofilms cultured in the freshwater of the middle and upper reaches of the same river and in the estuary area of the lower reaches of the river were significantly different.Furthermore,the Nanopore DNA sequencing approach with the advantage of creating long DNA sequence reads revealed the diversity of bacterial strains on microplastic biofilms.After continuous microplastic exposure for 21 days,microplastic accumulation was observed in the zebrafish intestines.Although microplastic exposure did not significantly change the K,HSI and GSI of adult zebrafish,the reactive oxygen species levels were significantly increased in zebrafish brain,liver and gonad in the higher concentration treatment groups(100 and 1000 ug/L).The apoptosis rate and apoptosis related gene expression were significantly increased in male zebrafish testis in the highest concentration group(1000 ug/L).Microplastic exposure(10,100 and1000 ug /L)did not significantly change the germ cells proportion for both male and female,but the basement membrane thickness of male zebrafish testis was significantly reduced in the highest concentration group(1000 g/L).Microplastic exposure did not significantly affect the sex hormone levels,but significantly altered the expression of sex hormone synthesis related genes in zebrafish.In addition,microplastic exposure had no significant effect on the egg production and fertilization of parental fish,and the hatching,body length,malformation rate,and mortality of offspring generation did not change significantly.The investigation of the growth,development and behavior of zebrafish embryos and larvae showed that carbamazepine at environmental concentration(1 ?g/L)could interfere with the growth and development of zebrafish embryos and accelerate their growth,leading to increased body length and accelerated yolk sac absorption.Microplastic accumulation was observed in the larvae exposed to microplastics(1 ?m;polystyrene),but the growth and development of embryos and larvae did not change significantly.Carbamazepine exposure significantly enhanced the spontaneous movement of zebrafish embryos,and increased the activity and touch response of fish larvae.Microplastics(1 ?m;polystyrene)significantly inhibited the swimming competence of zebrafish larvae,reporting a decrease in swimming speed and swimming distance.The results of gene expression analysis showed that carbamazepine exposure significantly increased the expression of neural development related genes(gfap,hu C,neuro D and ngn1)in zebrafish larvae,while microplastic exposure(1 ?m;polystyrene)significantly increased the expression of oxidative stress and inflammation related genes(cat and il1b)in zebrafish larvae.This study revealed the potential toxic effects of two typical emerging environmental pollutants in aquatic ecosystems and their complex toxic mechanisms,and can provide reference for future studies addressing the toxic effects and mechanisms of emerging environmental pollutants on aquatic organisms.This study has implications in managing aquatic environmental pollutants and risk assessment.