| Plastic products are widely produced and used,while providing convenience in life,it also causes a series of environmental problems.Plastics are difficult to degrade after entering the environment,and after a series of pathways,they can be decomposed into plastic fragments with a particle size of less than 5mm.Plastic,Microplastic Particles,MP),microplastic pollution has now become a serious global environmental problem.In recent years,the related toxicology research of microplastics has increased.In this study,the free-living nematodes of Dongzhai Port mangroves were used to explore the toxic effects of MP on the life history of Viscosia heterolaima,and to understand their toxic effects and ecological risks on small benthic animals.First,the concentration and chemical composition of Dongzhaigang mangrove microplastics were measured;secondly,the corn agar medium was used to culture the free-living nematode Viscosia heterolaima in Dongzhaigang mangrove,and the life history was observed by orthogonal test.The experiment determined the optimal conditions for nematode indoor life;then,the corn agar nematode growth medium was used as the control dish,and the fluorescent MP was evenly mixed in the medium as the exposed group dish,and the microplastics of different diameters were observed on the Viscosia heterolaima.The mortality rate of heterolaima,the number of nematodes gestating eggs,the time of monitoring embryo development,the number of offspring,etc.,and the distribution of microplastics with different particle sizes in the nematode Viscosia heterolaima was analyzed,and the life history of free living nematodes in Dongzhaigang mangroves was comprehensively evaluated by microplastics Impact.The research results are as follows:At the 9 mangrove forest sampling points in Dongzhai Port,the mass concentration of sampling point 1 is the lowest at 1.41±0.20 mg·kg-1,and the highest sampling point of No.7 was 11.13±2.52 mg·kg-1;the number and concentration were 37.49±6.78 n·kg-1,839.51±399.32n·kg-1respectively,among which,the elastic fiber(EF)accounted for57.02%,followed by the film type(SF)accounted for 21.11%;and The fiber-producing polymers are polypropylene and polyvinyl chloride;microplastic films are identified as polyethylene and polypropylene polymers;the foaming type is polystyrene;and the chip type is polyamide.The embryonic development of mangrove nematode Viscosia heterolaima has a developmental duration from one cell to the worm phase is,1cell period of 146.71±7.48min;2 cell period of 100.00±6.80min;4 cell period of 112.71±8.17min;multicellular period of 353.43±9.47 min:blastocyst stage 481.14±9.92min;gastrula stage 574.71±9.76 min;worm stage 1991.71±22.78min,The average embryo development time was62.67±1.28 hr,freshly hatched nematodes are transparent throughout the body,with a body length of 528.33±85.86?m,and stop growing around 23 d,The body length of adult is 2958.22±143.00?m,the maturity period of the nematode is 12–18d,and the life expectancy is about 46 d.The population density of Viscosia heterolaima was the highest when the temperature was 25?and the salinity was 20‰.Toxicity study of microplastic particles on Viscosia heterolaima.The results show that the concentration of microplastics on nematode lethality has a wireless relationship.Different particle sizes(0.1,1.0,3.0,5.0?m)can cause nematode death,among which,3?m particle size microplastics had the highest lethal rate to nematodes,with an average lethal rate of 24.17%,which was significantly different from the control group(P<0.01);the concentration was 2 mg·L-1.After exposure to different particle size microplastics,all It can inhibit the number of eggs in the nematode Viscosia heterolaima,prolong the embryonic development time of the nematode,and significantly reduce the number of nematode offspring,thereby affecting its life history.Among of which,the particle size of3?m is the most toxic to the nematode.Microplastics with different particle sizes are distributed in the nematode body.3?m microplastics have the strongest fluorescence intensity.In this study,we conducted a systematic survey on the pollution of mangrove microplastics in Dongzhai Port,Hainan,China,and studied the abundance,mass concentration,type,distribution and surface characteristics of microplastics in the sediments of Dongzhai Port,Hainan.The toxic effects of microplastic particles of different particle sizes on nematodes Viscosia heterolaima were systematically compared,and the particle size-dependent toxicity of microplastic particles was revealed.However,the influence mechanism of microplastic particles on marine nematodes is more complicated,and it is worth further study.This study lays a theoretical foundation for systematically evaluating the ecological risks of microplastics and formulating effective protection strategiesand thehealth effects of MP in the environment cannot be ignored. |
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