Combined Toxic Effects Of Polyvinyl Chloride Microplastics And Copper On Sebastes Schlegelii

With the widespread use of plastic products,microplastics(MP_S)pollution has become a major environmental issue of global concern.MP_Sin the ocean can adsorb heavy metals in the environment and have a compound effect on marine organisms.Therefore,the combined toxic effects of MPs and heavy metals in the environment are attracting more and more attention.As fish is an important source of animal high-quality protein for human,the accumulation of microplastics and heavy metals in fish and their potential effects on fish deserve special attention.In this study,the contents of heavy metals Cu,Zn,Pb,Cd,Cr and As in the tissues of five sea fish with important commercial value in Chinese offshore aquaculture were determined by ICP-MS method and their potential risks were analyzed.The effects of polyvinyl chloride(PVC)microplastics and copper(Cu)on growth physiology and liver toxicity of Sebastes schlegelii juvenile fish were investigated.In order to provide a theoretical basis for the objective assessment of marine ecological risks of microplastics and heavy metals.The main results of this study are as follows:1.Analysis of heavy metal content in fishery organisms in Bohai SeaIn order to assess the heavy metal pollution level of marine economic organisms,five economic fish species Setipinna taty,Scomberomorus niphonius,Pampus argenteus,Trichiuridae multicus and Engraulis japonicuswere were collected in the Bohai Sea.The contents of heavy metals(Cu,Zn,Pb,Cd,Cr,As)in fish muscle were analyzed and compared with those in fish collected from the yellow Sea,Laizhou Bay,Daya Bay and the South China Sea reported in literatures.It was found that the contents of heavy metals in organisms from Bohai sea were all lower than the limits recommended by FAO or China,and the target risk coefficients(THQ)of Cu,Zn,Pb,Cd,Cr and As caused by eating fish S.taty,S.niphonius,P.argenteus,T.multicus and E.japonicuswere from Bohai Sea were all less than 1,indicating that eating these fish has no potential harm to human health.The contents of heavy metals in organisms showed obvious spatial differences among different marine organisms and different regions,which may be related to the living environment of organisms.2.Effects of combined exposure of microplastics and Cu on growth and physiology of S.SchlegeliiTo investigate the effects of combined exposure of microplastics and Cu on growth physiology of S.Schlegelii,one control group(without microplastics and Cu)and three treatment groups(microplastics group,1.0×10~4particles/L PVC,copper group,200μg/L Cu and microplastics+copper group,1.0×10~4particles/L PVC+200μg/L Cu)were set up in this experiment.Juvenile fish were exposed to three treatment groups for 15 days,and the growth parameters,respiration rate and oxygen consumption rate of S.Schlegelii were measured and their tissue morphology were observed.The results showed that the body weight growth rate and specific growth rate of larvae were significantly reduced in all exposure groups,indicating that the growth and energy reserve of larvae were inhibited exposure to pollutants.Exposure to single microplastics and PVC+Cu combined groups had no effect on survival rate,condition factor and viscera index,but significantly increased hepatosomatic index of juvenile S.Schlegelii,the results showed that single microplastics and PVC+Cu combined exposure affected the liver of juvenile S.Schlegelii.Exposure to microplastics,copper,microplastics+copper significantly reduced the respiratory rate and oxygen consumption rate of juvenile fish,indicating that both microplastics and copper can inhibit the respiration of juvenile fish.After exposure to microplastics and PVC+Cu combined group,lesions occurred in gallbladder,liver and spleen of juvenile fish.3.Combined exposure of microplastics and Cu to liver toxicity of Sebastes SchlegeliiIn this experiment,S.Schlegelii was exposed to three treatment groups for 15 days,and the metallothionein,lipid metabolism indices and antioxidant enzyme activities of S.Schlegelii were determined.The results showed that the content of metallothionein(MT)in fish was significantly increased by single exposure to copper and PVC+Cu combined exposure to copper,and MT in combined exposure to copper was significantly higher than MT in PVC+Cu combined exposure to copper,suggesting that microplastics increased the bioavailability of copper when exposed to both microplastics and copper.Single exposure to microplastics or copper increased the activities of alanine aminotransferase(ALT)and aspartate aminotransferase(AST),and the contents of cholesterol(T-CHO)and triglyceride(TG),indicating the lipid metabolism disorder of juvenile S.Schlegelii.Exposure to the PVC+Cu combined group reduced the activities of ALT and AST,and the contents of T-CHO and TG.These results suggest that the transport of microplastics leads to increased accumulation of copper in the liver and greater toxicity to the organism.Exposure to pollutants significantly increased the activities of superoxide dismutase(SOD)and catalase(CAT)and the content of malondialdehyde(MDA),which resulted in tissue damage and oxidative stress of S.Schlegelii.From what has been discussed above,The contents of heavy metals Cu,Zn,Pb,Cd,Cr and As in muscle of S.taty,S.niphonius,P.argenteus,T.multicus and E.japonicuswere in Bohai sea economic fish are within acceptable range.Eating these fish has no potential harm to human health.Under the conditions of this study,compared with single microplastics and Cu group,PVC+Cu combined group has a greater effect on the growth and survival and lipid metabolism of juvenile S.Schlegelii,and has greater oxidative damage.These results indicate that the combined exposure of microplastics and Cu has a greater toxic effect on marine fish,which provides a scientific basis for the objective assessment of marine ecological risks caused by combined exposure of microplastics and Cu.