Succession Of Dominant Species Of Phytoplankton And Its Comparison With Peripheral Water In Dishui Lake

Dishui Lake is located in Pudong Lingang New City,Shanghai,which is the center of Lingang New City Water System.Dishui Lake plays an important role in shaping the urban landscape ecology and microclimate.Its water quality is directly related to the future city development and tourism of Lingang New City.In recent years,the water in the external water body no longer flows into the lake area,mainly relying on natural rainfall to replenish water.The quality of the nearby water environment will still affect the water quality of the drip lake.From January 2016 to December 2017,the laboratory conducted a comprehensive sampling survey of phytoplankton in the surrounding waters and the Dishui Lake,and compared the differences and linkages between the phytoplankton community structure in the Dishui Lake and its surrounding waters.Combined with the investigation of phytoplankton in Dishui Lake since 2006,this study further explored the succession of phytoplankton community in Dishui Lake,and explored the correlation between dominant dominant species and physicochemical factors of phytoplankton in Dishui Lake.The main results are as follows:1.From January 2016 to December 2017,102 species of phytoplankton were identified in the Lake,belonging to 57 genera of 8 phyla.The abundance of phytoplankton was 360.7×10~4 ind/L,and the average biomass was 2.47 mg/L.The dominant species of phytoplankton are:Merismopedia minima and Pseudanabaena sp.,Chlamydomonas globosa and Spermatozopsis,Cyclotella sp.,Skeletonema potamos,Cryptomonas erosa and Cryptomonas acuta,Chromulina pygmaea.2.From January 2016 to December 2017,167 phytoplankton species were identified on the outskirts of Dishui Lake,belonging to 80 genera of 8 phyla.The abundance of phytoplankton was 1071.224×10~4 ind/L,and the average biomass was6.13 mg/L.The dominant species of phytoplankton in the external water bodies are:Microcystis sp.,Merismopedia minima,Pseudanabaena sp.,Oscillatoria sp.,Chromulina pygmaea,Synura sp.,Gymnodinium sp.,Cyclotella sp.,Melosira varians,Skeletonma potamos,Carteria sp.,Chlamydomonas globosa,Scendesmus dimophus,Chlamydomonas sp.,Spermatozopsis sp.,Cryptomonas erosa and Cryptomonas acuta.3.Based on the difference in the amount of phytoplankton biomass in the Dishui lake,cluster analysis was performed using SPSS software to divide the dripping water lake and its surrounding water into five types of water.The number of phytoplankton species and the community structure of phytoplankton in the five habitats are quite different.The number of phytoplankton is the lowest in the lake and the highest in the center of the farm.From the comparative analysis of phytoplankton community structure and physicochemical factors,it can be concluded that there are significant differences between various types of water bodies in the lake area and the surrounding water bodies.4.Combined with the investigation of phytoplankton in the lake from 2006 to2017 in the laboratory,the main results are as follows:From the change in the number of phytoplankton species in the Dishui lake,the number of phytoplankton species reached the highest in 2009,after which the number of species fluctuates between 82-102 species.The biomass of phytoplankton showed a decreasing trend.The phytoplankton biomass was 41.41mg/L in 2006 respectively.By2017,the phytoplankton biomass was only 2.59mg/L.From the phytoplankton dominant species change in the Dishui Lake,Chromulina pygmaea was a long-term dominant species from 2006 to 2008.During this period,the biomass of the Cyanophyta was also high.In 2009-2013,the Gymnodinium sp.became a dominant species.Since 2009,the Cryptomonas acuta and Cryptomonas erosa biomass have increased.Skeletonema potamos,which emerged in 2015,have become The dominant species of Dishui Lake is currently stabilizing its bio-community structure.The phytoplankton species,biomass,the proportion of biomass in each gate,and the dominant species in each season have also gradually stabilized.Analyzing the main environmental factors of the succession of phytoplankton dominant species in Lake,the main environmental factors affecting the long-term succession of phytoplankton dominant species are Sal,COD and pH;secondly,the main environmental factors affecting the seasonal succession of phytoplankton are WT,TP;In the long-term succession of Dishui lake ecosystems,as the salinity and pH of Dishui lake decrease,salt and alkali-tolerant species decrease,and freshwater species increase;Dishui lake has higher nutrient concentrations and phytoplankton biomass.The decrease indicates that biological remediation plays a crucial role in controling phytoplankton.