| Microplastics in the marine environment has become one of the most concerning environmental problems.The capacity to adsorb persistent organic pollutants allows their ingestion and the accumulation of plastics in the aquatic food web to threaten the ecosystem further in addition to the ecotoxicity of microplastics.17?-estradiol and testosterone are typical environmental endocrine disruptors.Studies have shown that they are widely distributed in land and water.In our study,we selected a common zooplankton in coastal areas,Brachionus plicatilis,as the test animal.The drugs used in the experiment were polystyrene microplastics with three particle sizes(50 nm,100 nm,500 nm)and 17?-estradiol and testosterone.In single and combined exposure experiments,the main lifehistory and life table parameters of rotifers were evaluated.The main results of the experiment are as follows:1.In the single exposure experiment of polystyrene microplastics,rotifers were exposed to polystyrene solutions with a concentration of 0,5,10,20,50 ?g/m L and a particle size of 50 nm,100 nm,and 500 nm.The results showed that in the 50 nm microplastics group,the overall vitality of rotifers was significantly reduced.The higher the concentration of microplastics,the stronger the toxicity.For example,the time to first batch of eggs and time to first larvae were significantly prolonged,the survival time and offspring were significantly reduced,and the 96 h population growth rate dropped significantly.In the highest concentration group,the survival time of rotifers was less than 100 h,and they did not carry eggs during the entire life cycle,the population of rotifers increased negatively after 96 h exposure.however,in the 100 nm and 500 nm experiments,there was no adverse effect on the survival of rotifers under all concentration conditions.2.In the 17?-estradiol single exposure experiment,the rotifers were exposed to the 17?-estradiol solution with a concentrations of 0,1,10,100,and 1000 ?g/L.In all experimental groups,rotifers are living well.For example,the time to first batch of eggs,time to first larvae,reproduction time,survival time,total offspring per female were all normal,The single exposure of 17?-estradiol did not cause adverse effects on rotifers.According to the results of the single exposure experiment of microplastics,the concentration of microplastics in the combined exposure was confirmed to be 10?g/m L,and the particle size was still 50 nm,100 nm and 500 nm.The combined exposure concentration of 17?-estradiol remained the same as in the single exposure experiment.The results show that the combined exposure toxicity of 100 nm,500 nm microplastics and 17?-estradiol is different from single exposure toxicity,and the combined exposurehas adverse effects on the survival and reproduction of rotifers.For example,at the higher concentrations of 17?-estradiol in the mixed solution group,the reproductive period and survival time of rotifers were shortened,and the age-specific survival rate,the number of offspring and age-specific reproduction rate decreased.In the combined exposure of 50 nm-estradiol,although compared with the blank control group,the presence of 50 nm microplastics in the mixed solution significantly extend the time to first batch of eggs,time to first larvae,the number of offspring was reduced.The 50 nm microplastics also reduces the age-specific survival rate and age-specific reproduction rate of rotifers,but the combined toxicity of17?-estradiol and microplastics is almost insignificant from the toxicity of a single exposure of 50 nm microplastics.3.In the testosterone single exposure experiment,the rotifers were exposed to the testosterone solution with a concentrations of 0,1,10,100,and 1000 ?g/L.In all experimental groups,the lifehistory parameters of rotifers such as the time to first batch of eggs,time to first larvae,reproduction time,survival time,total offspring per female,96 h population growth rate,etc,are not significantly different from those of the control group.In the combined exposure of microplastics and testosterone,the concentration,the particle size and experimental methods of testosterone and microplastics are consistent with the 17?-estradiol combined exposure experiment.In the 100nm-testosterone and 500 nm-testosterone combined exposure experiments,the population is excluded.In addition to the 96 h growth rate,testosterone and microplastics have no toxic effects on the lifehistory and life table parameters of rotifers,and there is no significant difference between the experimental results and the single exposure experimental results.In the 50 nm-testosterone combined exposure,similar to the 17?-estradiol combined exposure experiment,the presence of microplastics has a significant adverse effect on the survival of rotifers.However,except for the combined exposure mixed solution 1 ?g/L group,the first egg laying time was significantly different from the PS control group,and the combined toxicity was not significantly different from the single toxicity of the PS control group. |
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