Correlative Analysis And Characteristics Of Aquatic Plants And Water Environment In The Eastern Taihu Lake

Vigorous efforts have been made to improve the water environment of the Lake Taihu basin since the occurrence of cyanobacteria blooms.Although these efforts have produced some effects,Lake Taihu still faces severe cyanobacteria blooms every year.The intensity of cyanobacteria blooms has not declined significantly,instead aquatic plants in Lake Taihu have degraded seriously.In order to eliminate eutrophication in Lake Taihu,the restoration of aquatic plants is of great significance to improving the damaged water environment and enhancing the stability of aquatic ecosystems.in this paper,16 sampling points were selected in eastern Lake Taihu for field survey on aquatic plants in the lake area in spring,summer and autumn,and water samples were collected for testing.By applying hierarchical clustering and canonical correspondence analysis(CCA),the species and community characteristics of aquatic plants in different seasons and the spatiotemporal variation characteristics of water environmental factors in eastern Lake Taihu were discussed;the response relation between the distribution of aquatic plants and water environmental factors in eastern Lake Taihu was revealed;and the growth characteristics and succession laws of aquatic plants in eastern Lake Taihu was discussed.Main conclusions of this research are as follows:(1)From 2020 to 2021,a total of 60 species of aquatic plants belonging to 26 families and49 genera were surveyed in eastern Lake Taihu.Most of the aquatic plants are tropical,with obvious north-south transitional features in flora.(2)The survey discovered that aquatic plant communities in eastern Lake Taihu feature nonuniform spatial distribution,with the species abundant of aquatic plants in the eastern Lake Taihu area.Submerged plants are mainly distributed in Xuhu Bay and the original purse seine farming area of the eastern Lake Taihu area,floating plants are mainly distributed in Zhenhu Bay and Guangfu Bay,and emergent plants are distributed along the lakeshore.Major plant communities found in the survey are Phragmites australis community,Nelumbo nucifera +Zizania latifolia communities,Alternanthera philoxeroides community,Trapa bispinosa-Ceratophyllum demersum communities,Potamogeton wrightii community,Elodea nuttallii community,Myriophyllum spicatum community,Potamogeton crispus community and Ceratophyllum demersum community,etc.(3)The growth and distribution of aquatic plants in eastern Lake Taihu exhibit noticeable seasonal variation.In spring,Potamogeton crispus,Elodea and Potamogeton wrightii Morong are dominant species,while in summer,dominant species are Myriophyllum spicatum,Ceratophyllum and Trapa bispinosa Roxb.Emergent plants like Zizania latifolia and Phragmites australis are dominant species throughout the year,and floating plants like Trapa bispinosa Roxb and Nelumbo nucifera have obvious advantages in autumn.(4)The water environmental factors in eastern Lake Taihu vary with time and space.The p H value and conductivity(COND)of the water body in descending order are summer >spring > autumn,and the water body is slightly alkaline.The dissolved oxygen(DO)content in water body in descending order is: spring > autumn > summer.The total nitrogen(TN)content in descending order is: spring > summer > autumn,and fluctuates greatly and reaches the class IV water standard in spring and summer,and class II water standard in autumn.The peak value of Sampling points S10 and S11 in spring and summer was 3.68mg/L and 3.59mg/L respectively.The total phosphorus(TP)content in descending order is: autumn > spring >summer,and is the lowest in summer,and reaches the class II water standard in summer,and class III water standard in spring and autumn.(5)Canonical correspondence analysis(CCA)can better explain the relationship between aquatic plants and water environmental factors.The impact of water environmental factors on different plants differs with season,and the relationship between water environmental factors in different seasons and sampling points also varies.Key water environmental factors affecting aquatic plant communities are water temperature(T),total nitrogen(TN)and dissolved oxygen(DO)in spring,total phosphorus(TP)and dissolved oxygen(DO)in summer,and water temperature(T)and dissolved oxygen(DO)in autumn.(6)It is recommended to manage and control the above-mentioned environmental factors that deliver a greater impact on the growth and distribution of aquatic plants in eastern Lake Taihu.Reasonable types and configurations of aquatic plants shall be selected according to the pollution degrees and water qualities of the lake areas.In addition,it is necessary to strengthen the supervision of lake wetlands and the maintenance of the restoration areas for aquatic plants.The dead and decaying plants,the overgrown floating plants and such alien invasive species as Alternanthera philoxeroides in the lake areas shall be collected and harvested timely.