Study On Phytoplankton Community Structure Of Dogai Coring In Tibet

Salt Lake is a special kind of lake,which is often defined as a variety of lakes with a salt content of 3 g/L.China has more than 1,000 salt lakes with an area of 41,000 km~2,which is mainly distributed in the western and northeastern parts of China.The Tibet Plateau is the highest and largest salt lake region in the world.Scholars at home and abroad have studied Tibet's mineral resources in the early stages,and have paid more and more attention to their biological resources in the later period.Dogai Coring is located in the north-central part of the North Qiangtang Basin in Tibet.Due to the fact that Dogai Coring is located in the unpopulated area of northern Tibet in the Naqu region,the natural environment is harsh and research conditions are inconvenient.Research on salt springs,brines,lithium and potassium minerals has been extensive,but there has been almost no research on the biological resources of the Dogai Coring.This paper investigates and analyzes all lakes to understand the horizontal characteristics of the phytoplankton community structure in Dogai Coring.Through the comparison of the phytoplankton community structure among the surface,the middle the bottom layer,the vertical distribution characteristics of phytoplankton are explored,which lays a foundation for further research on the Dogai Coring.The main results are as follows:1.A total of 231 species and varieties of phytoplankton were identified from the 58 sampling points of Dogai Coring,belonging to 4phylums and 72 genera.Among them,39 species of 17 genuses belong to Cyanophyta,4 species and 6 species belong to Bare Algae,and 19 species and 27 species belong to Chlorophyta.Diatom algae species are the most abundant(164 species of 32 genera),accounting for 71.00%of the total species,followed by Cyanophyta(39 species of 17 genera)and Chlorophyta(19 genera,27 species),accounting for 14.72%and 11.69%of the total species,respectively.the lowest number of species(4 genera and 6 species),accounting for 2.60%of the total species.According to the proportions of cell biomass and densities,the algae properties of lakes were divided.The results showed that the Dogai Coring salt lakes were Bacillariophycophyta-type lakes,and Bacillariophycophyta had obvious advantages.According to the dominance degree is greater than or equal to 0.02 to determine the dominant species of a community,so there are 2 dominant species of surface phytoplankton at 58 sampling points of Dogai Coring,namely,Nitzschia sp.and Navicula vulgaris Navicula.Four dominant species of phytoplankton,including the Navicula sp.,Hantzschia sp.,Hantzschia amphioxys,and Nitzschia sp.;The dominant species of phytoplankton in the surface and bottom of lake are all belong to Bacillariophycophyta,and the top two species in terms of dominance are Nitzschia sp.and Navicula sp.The average biological density of phytoplankton in surface waters of58 strains of Dogai Coring was 8.44×10~4 cell/L,and the average cell biomass was 0.1021 mg/L.The average biological density of phytoplankton in the bottom water was 68.43×10~4 cell/L,and the biomass was 0.8198 mg/L.The Shannon-Wiener diversity index(H')of surface waters at the 58sampling points of Dogai Coring was 1.51±0.33;the average of Margalef's richness index(D)was0.74±0.30;the average of the Pielous evenness index(J)was0.76±0.15.The H'-average value was 1.46±0.40,the D-average value was 1.04±0.45,and the J-average value was 0.57±0.15.2.A total of 109 species and varieties of phytoplankton were identified from 10 sampling points of Dogai Coring,of which the depth were deeper than 15m,belonging to 4 phylums and 72 genera.Diatom algae species are the most abundant(86 species of 20 genera),accounting for 78.90%of the total species,followed by Cyanophyta(9 species of 6genera)and Chlorophyta(9 genera,8 species),both accounting for 8.26%of the total species.The lowest number of species(4 genera and 3 species),accounting for 0.92%of the total species.There are 5 dominant species of superficial phytoplankton at 10sampling sites in Dogai Coring,all belonging to Bacillariophycophyta:Navicula sp.,Nitzschia sp.,Hantzschia amphioxys,Hantzschia amphioxys var.linearis,and Hantzschia sp.;four dominant species of mid-water phytoplankton,of which three are Bacillariophycophyta,one belongs to the Chlorophyta,including navicia sp.,Nitzschia sp.,Hantzschia sp.,and Chlamydomonas globose;five species of dominant phytoplankton in the bottom water,of which four belong to the Bacillariophycophyta,one belongs to the Cyanophyta,including Rhopalodia sp.,Navicula sp.,Hantzschia sp.,Hantzschia amphioxys,and Hantzschia amphioxys var.linearis;The dominant species of phytoplankton in the surface,middle and bottom layers of water are mainly composed of Bacillariophycophyta.The average cell density of surface phytoplankton in the 10 sampling points of Dogai Coring was 1.59×10~4 cell/L,and the average cell biomass was 0.0303 mg/L.The average cell density of phytoplankton in the middle water was 3.81×10~4 cell/L,and the biomass was 0.0278 mg/L.The average bio-density of bottom phytoplankton was 140.65×10~4 cell/L and the biomass was 1.0490 mg/L.The H?mean value of surface water phytoplankton at 10 points of Dogai Coring was 1.61±0.33;the D-average value was0.79±0.19;the J mean was 0.73±0.12;the H?-average value of phytoplankton in the middle layer water was 1.47±0.55;the D-average value was 0.85±0.19;the J-average value was 0.67±0.25.The H?-average value of phytoplankton in the bottom layer water was 1.41±0.52;the D-average value was 1.32±0.55;the J-average value was 0.49±0.15.3.A cluster analysis of a total of 116 samples including tables and bottom water covering 58 sampling points across the entire lake revealed that the surface layer is a type and the bottom layer is a type.In the horizontal direction,the number of phytoplankton species decreases from low to high longitude,and decreases from high latitude to low latitude.The vertical distribution pattern is that the number of phytoplankton species gradually increases from the surface layer to the middle layer to the bottom layer.4.By acidifying the samples to remove other algae and the organic matter of the diatom,coupled with highly transparent Naphax adhesive sheet,the internal structure of the diatom is more clearly observed and accurately identified.