Community Assembly And Biodiversity Patterns Of Benthic Diatom In Anzhaoxin River Basin

River ecosystem is one of the hotspots of global biodiversity research,and it provides an important guarantee for maintaining the biological community and habitat environment in the river.Exploring the formation and maintenance mechanism of biodiversity has always been the core issue of ecological research.Benthic diatoms are important primary producers in river ecosystems.Changes in their community structure often reflect changes in surrounding environmental conditions and are often used in water environment monitoring.The Anzhaoxin River Basin is a typical river ecosystem.It is located in the middle of the Songnen Plain and runs through the main urban area of Daqing City.It is an important source of power to reduce the flood control pressure and pollutant discharge of the river.However,the research on the construction mechanism of benthic diatom communities in river ecosystems in my country is still insufficient,so it has important ecological significance for studying the diversity of benthic diatoms in the Anzhaoxin River Basin and their maintenance mechanisms.In this study,specimens were collected and identified from 37 sampling points in the Anzhaoxin River Basin in the spring,summer and autumn of 2019 and 2020,and the physical and chemical indicators of each sampling point were determined.Using redundancy analysis(RDA),canonical correspondence analysis(CCA)and other analytical methods,study the diversity characteristics and community construction of benthic diatoms from the dimension of the species diversity of benthic diatoms,and explore the effects of their community construction in combination with water environmental factors The main driving factor.At the same time,a preliminary assessment of the water health status of the Anzhaoxin River Basin from the perspective of biological and non-biological factors provides a reference for the restoration of damaged river ecosystems and diversity protection in my country.The main findings of this paper are as follows:1.From 2019 to 2020,130 species of benthic diatoms were identified,belonging to45 genera,2 classes,7 orders,10 families.Nitzschia has the most species,followed by Navicula.In 2019,the average abundance of benthic diatoms in the Anzhaoxin River Basin was 4.32×10⁴ ind./cm²,and the average abundance in autumn 2020 was 6.84×10⁴ind./cm².The abundance of benthic diatoms and their density change significantly in time and space distribution.The overall community structure is mainly Navicula and Nitzschia.2.A total of 47 dominant species of benthic diatoms were identified from 2019 to2020.A total of 17 dominant species included:Cymbella excisiformis Krammer?Navicula veneta Kützing?Mastogloia smithii var.amphicephala Grunow?Cyclotella meneghiniana Kützing?Tabularia fasciculata Williams&Round?Navicula cincta(Ehrenberg)Ralfs?Amphora veneta Kützing?Nitzschia palea(Kützing)W.Smith?Nitzschia reversa W.Smith?Ulnaria danica(Kützing)Compère&Bukhtiyarova?Fragilaria capucina var.vaucheriae(kützing)Lange-Bertalot sensu lato?Pleurosigma decorum W.Smith?Nitzschia capitellata Hustedt?Rhopalodia gibba O.Müller?Nitzschia clausii Hantzsch?Surirella brebissonii Krammer&Lange-Bertalot and Gomphonema parvulum(Kützing)Kützing.SIMPER analysis and ANOSIM analysis show the succession characteristics of dominant species in different seasons.The results show that in spring 2019,Navicula associata and Gomphonema parvulum dominate,while in summer and autumn it is Cyclotella meneghiniana and Diatoma vulgaris has an advantage.3.During 2019-2020,the Shannon-Weaver index(H')of each sampling point in the Anzhaoxin River Basin varies from 0.29 to 5.03;the Simpson Index(D)varies from0.06 to 0.96;the Margalef index(H)varies from 0.16 to 5.88;the Pielou index(J)varies from 0.07 to 0.96;the variation range of diversity threshold(Dv)is 1.58?5.55;the percentage of motile diatoms(M)varies from 0.0008 to 5.29;the diatom quotient index(DQ)varies from 1.48 to 16.35.The results of the seven diversity indexes show that the Anzhaoxin River Basin has rich species of benthic diatoms,with good diversity and obvious changes in the temporal pattern.In terms of spatial pattern,the reservoir area and lake area are affected by environmental factors such as rainfall,flow rate and flow,and the hydrological situation changes significantly.Therefore,the process of community construction is mainly affected by environmental screening.4.During the study period,the water temperature of the Anzhaoxin River Basin varied between 4.3-27.4?;the p H fluctuated between 7.47-9.62;the conductivity varied between 124-5954?S/cm;the variation range of dissolved oxygen was 2.4-18.6mg/L;the turbidity varies between 7.8-200 NTU;the variation range of total nitrogen is0.43-2.28 mg/L;the variation range of total phosphorus is 0.01-2.04 mg/L;the variation range of chemical oxygen demand is 1.24-29.69 mg/L;the five-day biochemical oxygen demand fluctuates between 0.10-15.53 mg/L.Pearson correlation analysis showed that Sp C.was extremely significantly positively correlated with TN,TP and COD_Mn;WT was extremely significantly negatively correlated with DO and p H;p H was extremely significantly negatively correlated with Sp C.,TN,and TP;Tur.was extremely significantly correlated with DO and COD_Mn.BOD₅ showed a significant negative correlation.5.The benthic diatom community pattern in the Anzhaoxin River Basin is closely related to water environmental factors.CCA and RDA analysis show that in 2019,TP(P=0.002)?WT(P=0.002)?DO(P=0.002)?BOD5(P=0.002)and TN(P=0.006)are the main environmental factors affecting the formation of benthic diatom communities in the Anzhaoxin River Basin;WT(P=0.006)in the fall of 2020 will drive changes in the structure of benthic diatom communities Main environmental factors.6.This study evaluates the water quality of the Anzhaoxin River Basin based on a variety of methods.The evaluation results based on the environmental quality standards of surface water showed that most of the water bodies were Class III and IV in the two years,the water quality was in a state of medium pollution,and the main pollution indicators were TP and COD_Mn.Based on the comprehensive nutritional status index method,the water body is evaluated as mild to moderate eutrophication.Based on the pollution indicator,the water body is evaluated as eutrophication and the salinity of the water body is high.The evaluation result based on the diversity index shows that the water body of the Anzhaoxin River Basin is lightly polluted to moderately polluted.Based on the above water quality evaluation methods,the overall water quality of the Anzhaoxin River Basin from 2019 to 2020 is estimated to be in a moderately polluted state.