| At present,eutrophication of rivers is one of the common water environmental problems at home and abroad.As a modern international metropolis with developed water system,Shanghai attaches great importance to the eutrophication of water environment.Plankton can be used as an important water quality evaluation indicator because of its response to environmental factors,and it is often associated with eutrophication of water.Shanghai lacks the research of large area of the plankton in river water system,therefore,this thesis studied the spatial distribution features of plankton community structure in the autumn of 2018 and the summer of 2019 in Shanghai rivers which were divided into city center,new urban and rural areas rivers,and evaluated water quality.This paper is aim to provide data support for the identification of river eutrophication in different regions of Shanghai,and to provide decision-making basis for the government to carry out scientific management of river water environment in Shanghai.The main research results are as follows:(1)149 species and 185 species of phytoplankton were identified in autumn and summer in the surveyed river channels of the city,with the major species of Chlorophyta and Cyanobacteria.The density and biomass of phytoplankton in summer were higher than that in autumn,and the average density and biomass of phytoplankton in rural river channels were the largest in autumn and summer,respectively,448.54×104 cells·L-1 and 4.50 mg·L-1,2045.12×104 cells·L-1 and 22.51 mg·L-1.The dominant species of phytoplankton in autumn and summer were 4 and 5,mainly Cyanobacteria.(2)65 species and 85 species of zooplankton were identified in autumn and summer in the surveyed river channels of the city,mainly rotifers and protozoa.Both the density and biomass of zooplankton in summer were higher than that in autumn,and the average density and biomass of zooplankton in rural river channels were the largest in autumn and summer,with 5472.11×104 cells·L-1 and 0.79 mg·L-1,6851.73×104 cells·L-1 and 7.14 mg·L-1,respectively.The dominant species of zooplankton in autumn and summer were 11 and 20,mainly protozoa and rotifers.(3)The main factors affecting phytoplankton community structure in autumn and summer were transparency(SD),total phosphorus(TP),total nitrogen(TN),dissolved oxygen(DO)and turbidity(NTU),TN,NTU,SD and pH,respectively.Phytoplankton community in new town channels was mainly affected by TP and NTU in autumn.Rural areas are mainly affected by DO,SD and NTU.In summer,the downtown area was mainly affected by SD and pH.The new town was mainly influenced by the NTU and TN.The rural area was mainly influenced by the NTU.In autumn,Chlorophyll a(Chl.a),comprehensive water quality score(F)and SD were the main factors affecting zooplankton community,while in summer,the influencing factors of zooplankton community were not significant(P>0.05).In autumn,the samplings in rural areas had a close relationship with DO.(4)The result of water quality evaluation of physical and chemical indicators of water bodies is that most river water bodies were below class V.The current stock of zooplankton evaluation is in good agreement with the evaluation of physical and chemical indicators.The evaluation result is that the investigated channels were in a state of eutrophication-extreme eutrophication.Compared with other areas,the eutrophication of the rural river in Shanghai was more serious in summer,which needs to be paid more attention. |
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