聚苯乙烯微塑料和罗红霉素对斜生栅藻(Scenedesmus obliquus)和大型溞(Daphnia magna)的联合效应研究

Combined Effects of Polystyrene Microplastics and Roxithromycin on the Green Algae(Scenedesmus obliquus) and Waterflea(Daphnia magna)

近年来,微塑料(Microplastics,MPs)和抗生素成为受到广泛关注的新兴污染物。有关二者对生物体的单一毒性研究已经被广泛报道,然而它们对浮游生物的联合毒性研究还较为缺乏。文章的研究目的是明晰聚苯乙烯微塑料(PS-MPs)和大环内酯类抗生素罗红霉素(Roxithromycin,ROX)共存条件下,对浮游植物斜生栅藻(Scenedesmus obliquus)和浮游动物大型溞(Daphnia magna)的生物交互效应。通过水体暴露的方式,分别研究了MPs与ROX对小球藻和大型溞的单一和联合毒理效应。测试了不同暴露组中斜生栅藻的藻细胞密度、叶绿素a含量以及最大光化学量子产量(Fv/Fm)等生理指标,暴露液中ROX的浓度变化,大型溞的牧食率、滤水率以及超氧化物歧化酶(Superoxide Dismutase,SOD)和过氧化氢酶(Catalase,CAT)等抗氧化酶的活性响应。结果表明,PS-MPs和ROX联合暴露对斜生栅藻的生长具有显著的抑制作用,同时对其光合作用效率产生了一定的负面影响。相较于空白组,藻细胞密度、叶绿素a含量以及Fv/Fm分别下降了13.3%、9.5%和9.3%,但是二者联合暴露与单一暴露抑制效果并没有显著性差异;此外,PS-MPs和ROX的联合暴露对大型溞的觅食行为存在显著抑制作用,牧食率和滤水率相较于空白组分别下降31.3%和31.6%,且在二者共存条件下,PS-MPs能够降低ROX对大型溞觅食行为的影响;PS-MPs和ROX的联合暴露显著抑制了大型溞的SOD活性和CAT活性,这可能会导致氧化损伤的发生,且联合暴露会对大型溞SOD活性产生相加作用,对CAT活性产生轻微的协同作用。在今后的研究中,应进一步探索MPs和抗生素对浮游生物的长期交互效应,并对相关作用的机理进行深入研究。

In recent years,microplastics(MPs)and antibiotics have become widely concerned emerging pollutants.The single toxicity of the pollutants on organisms has been well documented.However,information on their combined toxicity to plankton remains limited.The purpose of this study was to clarify the interactive effects of the polystyrene microplastics(PS-MPs)and the macrolide antibiotic roxithromycin(ROX)on the phytoplankton Scenedesmus obliquus and the zooplankton Daphnia magna.The single and joint effects of MPs and ROX on S.obliquu.s and D.magna were studied through the water exposure route.In the present study,the algal cell density,the chlorophyll a concentration,the maximum quantum yield for primary photochemistry(Fv/Fm)of S.obliquu.s and the concentration of ROX in the exposed media were tested.Moreover,the ingestion and filtration rates of D.magna,as well as the antioxidant enzymes activity,including superoxide dismutase(SOD)and catalase(CAT),were tested.The results showed that the combined exposure of PS-MPs and ROX significantly inhibited the growth of S.obliquus,and had a negative impact on its photosynthesis efficiency.Compared with the control group,the algal cell density,chlorophyll-a content,and Fv/Fm in the co-exposure group decreased by 13.3%,9.5%,and 9.3%,respectively.However,there were no differences in the inhibitive effects between the co-exposure group and single exposure groups.In addition,the co-exposure of PS-MPs and ROX significantly inhibited the foraging behavior of D.magna.In the co-exposure group,the ingestion and filtration rates decreased by 31.3% and 31.6%,respectively,compared with the control group.Under the co-exposure conditions,PS-MPs could reduce the inhibitive effects of ROX on the foraging behavior of D.magna.The co-exposure of PS-MPs and ROX significantly inhibited the SOD activity and CAT activity of D.magna,which might lead to oxidative damage.The co-exposure might have an additive effect on SOD activity and a slight synergistic effect on CAT activity.In future works,the long-term interactive effects of MPs and antibiotics on plankton organisms and the underlying mechanisms should be further studied.