Spatial-Temporal Distribution And Simulation Of Zooplankton Community In Nansihu Lower Lake

Lakes,as one of the most important freshwater systems on land,play an indispensable role in maintaining ecological balance and realizing sustainable development.As the largest freshwater lake in northern China,Nansi Lake plays a dramatically significant role in regulating storage,irrigating,supplying potable water and so forth.Meanwhile,Nansi Lake boasts an unique strategic position in the South-north Water diversion project,thus,its water quality needs to be paid special attention.Aquatic organisms can sense the changes of water ecology promptly and acutely.Moreover,zooplankton is considered as an important link in the aquatic ecosystem,and the changes of its community structure can indirectly reflect the specific changes of the aquatic environment in this region,which is conducive to carrying out the water quality monitoring and protection of the Nansi Lake.Therefore,in order to ensure the water safety and maintain the water ecological balance in the surrounding areas,this paper establishes the protection and prediction mechanism of lake water ecological protection by virtue of the characteristics of zooplankton community structure as the monitoring index,so as to provide theoretical support for the maximum benefit of water transfer and the construction of a harmonious ecosystem.In this paper,according to the field-survey data of two water transfers in the lower lakes of Nansi Lake,the spatial and temporal variation of water quality parameters and the structural characteristics of zooplankton community distribution were sorted out and analyzed.The most critical environmental factors affecting the community structure were obtained through correlation analysis and redundancy analysis.On this basis,a multiple regression model between the two was further constructed.Subsequently,combined with the water quality model data of the subordinate lakes,the spatial distribution of the characteristic parameters of zooplankton in the subordinate lakes was simulated.The main achievements are as follows:(1)Collate the actual sampling data of zooplankton in the subordinate lakes of Nansi Lake,and analyze the spatio-temporal variation rules.The characteristics of zooplankton community structure(number of species,density biomass,dominant species,diversity index)showed that the values of each period of the water transfer cycle from 2020 to 2021 were higher than those of the same period from 2018 to 2019.In the same cycle,it was indicated that density and biomass presented the maximum distribution after water transfer,followed by that before water transfer,and the minimum distribution during water transfer,while other parameters presented the maximum distribution law after water transfer and the minimum distribution before water transfer.(2)Analyze the spatial-temporal variation of 10 environmental factors(total phosphorus,total nitrogen,permanganate,suspended matter,ammonia nitrogen,transparency,water temperature,dissolved oxygen,total dissolved solids,PH)in 6 samples.Pearson correlation analysis and redundancy analysis were conducted with the density,biomass,diversity index(Shannon-Wiener index,Pielou evenness index)of zooplankton.The results of the two methods were consistent.Then,the most critical environmental factors were selected as dissolved oxygen,water temperature,permanganate index,total dissolved solids,total phosphorus.Then the multiple regression model is constructed and the accuracy is verified.(3)A two-dimensional hydrodynamic and water quality model was constructed according to the basic data of the lower lakes of Nansi Lake,and four water quality indexes including dissolved oxygen,permanganate index,total dissolved solids and total phosphorus were input into the water quality model to obtain their distribution and evolution rules.Additionally,the water quality simulation data was verified with measured data.(4)The sub-lake was partitioned according to the hydrodynamic simulation results,and the calculation units were divided.Based on the regression model,the water quality simulation results were input into the model as input conditions.Finally,the characteristic parameter values of zooplankton in each calculation unit were obtained.According to the simulation results,the spatial distribution difference of zooplankton community structure was analyzed.The results showed that compared with the waterway area,the aquatic grass area enjoys the densest zooplankton distribution and the most abundant diversity.