Effects Of Combined Treatment Of Water Acidification And Microplastics On Submerged Plant Communities

Due to the impact of human activities and global change,the problems caused by microplastics and water acidification are seriously threatening the structure and ecological service function of freshwater ecosystem.Submerged plant community is an important part of aquatic ecosystem.The ecotoxicity of microplastics and water acidification on submerged plant community has not attracted enough attention.In this study,Vallisneria natans and Hydrilla verticillata,the common submerged plants in China,were used as the test plants.The microplastic concentrations of 50mg/L,100 mg/L and water acidification p H5.6,p H6.3,p H7.0as an experimental treatment,to explore the impact of the combined treatment of microplastic and water acidification on Vallisneria natans,Hydrilla verticillata and their communities,in order to provide theoretical support for the ecological risk assessment of microplastic and water acidification on aquatic ecosystem.The main results are as follows:1)The microplastic with the concentration of 50 mg/L significantly increased the total length growth rate and fresh weight growth rate of Hydrilla verticillata in mixed planting.Compared with the control,the microplastic at the concentration of 50 mg/L had a significant inhibitory effect on the branch number of Hydrilla verticillata,while 100 mg/L promoted it.Compared with the control,the addition of microplastics increased the specific leaf area of Hydrilla verticillata.100 mg/L of microplastics significantly stimulated the increase of soluble sugar content in mixed cultivated Hydrilla verticillata and Vallisneria natans.When the concentration of microplastics was 100 mg/L,the chlorophyll content of Hydrilla verticillata was significantly higher than 50 mg/L.At the concentration of 50 mg/L microplastic,the competitive ability of Hydrilla verticillata was significantly stronger than that of Vallisneria natans,and it may have an impact on the community structure of Vallisneria natans and Hydrilla verticillate.2)The decrease of p H(p H5.6 ～ 7.0)significantly inhibited the growth rate of total length and fresh weight of bitter grass planted alone.The treatment of p H5.6,p H6.3 increased the specific leaf area of all except Vallisneria natans planted alone when compared with p H7.0.The treatment of p H5.6 significantly reduced the soluble sugar content of single planting Hydrilla verticillata,but significantly increased the soluble sugar content of mixed planting Vallisneria natans when compared with p H7.0.Under the treatment of p H 6.3,the competitive ability of Hydrilla verticillata was significantly stronger than that of Vallisneria natans,and it may have an impact on the community structure of Vallisneria natans and Hydrilla verticillate.3)The combined treatment of microplastic and water acidification significantly inhibited the total length growth rate,fresh weight growth rate and branch number of Vallisneria natans,but significantly increased the specific leaf area of each tested plant at the same time.Under the combined treatment of microplastic and water acidification,the content of soluble sugar in each treatment group increased compared with the control group.Under the treatment of 50 mg/L +p H5.6 and 50 mg/L + p H7.0,the competitive ability of Hydrilla verticillata was significantly stronger than that of Vallisneria natans,and it may have an impact on the community structure of Vallisneria natans and Hydrilla verticillate.