| Eutrophication is one of the most challenging environmental problems in accordance with surface water.Urban lakes are characterized by shallow depth,slow flow rate,small surface area and frequent contact with urban population.Therefore,eutrophication of urban lakes has become an important and serious environmental problem in China.Cu SO4 is a traditional chemical algicide,which is widely used because of its low cost and easy availability.Therefore,based on the investigation and analysis of the water quality and algal community structure of urban lakes in different regions of China,this study takes Microcystis aeruginosa as the research object,and discusses the physiological and biochemical response of algal cells under the stress of copper sulfate in terms of the growth and photosynthetic activity of algal cells.Finally,copper sulfate was added to the raw water of urban lakes to analyze its effects on algae removal rate and community structure.The main research results are as follows:(1)The difference of algal community structure in 16 urban lakes of four regions was studied.The results showed that: 1)There were significant regional differences in algal density of urban lakes(P < 0.001),and the order of algal density in different regions was north,west,south and east.2)The identified algae taxa from 16 urban lakes were ascribed to 6 phyla–Cyanophyta(Cyanobacteria),Bacillariophyta,Dinophyta,Euglenophyta,Chlorophyta,and Chrysophyta.It is noteworthy to mention that Chlorophyta was the most common phylum,accounting for 57.19 % of the total algal community.At the genus level,the dominant genera were Synedra sp.,Chlorella sp.,Microcystis sp.,and Rhabdogloea sp.3)The symbiotic network analysis showed that the interaction between geographical pattern and algal organisms resulted in the unique algal community structure in different urban lakes.4)The redundant analysis(RDA)and structural equation modeling(SEM)analysis showed that water quality(TN,NO3--N)and geographical pattern had synergistic effects on algae communities in urban lakes.(2)Taking Microcystis aeruginosa as the object,and Cu SO4 was used as the algicide,the effects of different concentrations of Cu SO4 on the growth and photosynthetic activity of Microcystis aeruginosa were studied by analyzing the physiological and metabolic activities of algal cells,such as concentration of chlorophyll-a,parameters related to photosynthesis,antioxidant enzyme activity,ATP concentration,carbon metabolism activity and algae organic matter.The results showed that: 1)Cu SO4 could inhibit the growth of Microcystis aeruginosa cells,and the inhibition effect was more significant with the increase of concentration.After 72 days of treatment with 0.5 mg/L Cu SO4,the algal density decreased from 100×104 cells/m L to 66.09×104 cells/m L.2)Cu SO4 significantly affected the chlorophyll fluorescence parameters and inhibited the photosynthetic activity of Microcystis aeruginosa cells.In the analysis process of antioxidant enzyme activity,it was found that the enzyme activity of the treatment group increased to varying degrees within 24 h after treatment,and then gradually decreased,and with the increase of Cu SO4 concentration,the enzyme activity always maintained a high activity.3)The results of the study on the metabolic activity of carbon source showed that the carbon source utilization ability of the three states of algal cells was different,and the order of the carbon source metabolic activity of algal cells was the control group >0.2 mg/L > 0.5 mg/L。(3)From the perspective of practical application,different concentrations of Cu SO4 were added to the raw water of 6 urban lakes to study the effects of different concentrations of Cu SO4 on the algal community structure in lakes.The results showed that: 1)Different concentrations of Cu SO4 have different removal rates of algae and the removal rates of algae in different urban lakes are also different.For QX lake,the algae removal rate was 35 % under the stress of 0.2 mg/L Cu SO4,and 39 % under the stress of0.5 mg/L Cu SO4.2)The algal community structure of different urban lakes was no significant difference,with Cyanobacteria being the dominant group.The algal community structure at the genus level is also no difference,and Chlorella sp.is the dominant algae.3)Research results show that the residual copper content in different water bodies after 72 h after the application of the copper content decreased obviously,and the content is below the national surface water environment requiring Ⅴ type water standard of copper content(0.1 mg/L). |
