Research On Plankton Community Structure And Water Quality Evaluation In The Core Area Of Niulan River Fish Reserve

The Niulanjiang Fish Reserve is located in the middle reaches of the Niulan River in Qujing City,Yunnan Province.It involves Zhanyi,Huize and Xuanwei counties(cities and districts).It is the largest in Qujing City,the longest river course,and the most rare and endemic fish.Fish nature reserve.The starting point of the reserve is Deze Township,Zhanyi District,and the end point is Huohong Township,Huize County.The total length of the river is about 130km and the area is about 2500hm².The core area of the reserve is the Mazhang Village,Dajing Town,at the mouth of the Xize River,with a river length of about 80km and an area of about 1600hm².Since the establishment of the reserve,the plankton and water quality of the Niulan River Fish Reserve have not been systematically investigated.Plankton and water quality are the conditions on which fish live,and the advancement and construction of the Qujing She River Water Conservancy Project.The prosperity and development of the surrounding society and economy makes the investigation and research on the plankton and water quality of the Niulan River fish reserve,especially the core area,particularly important.This study used four seasons as the time division from January to October 2019 to investigate plankton in the core section of Niulan River Fish Reserve.The first anniversary of the survey time was January(winter),April(spring),July(summer),and October(autumn)in 2019.During the sampling survey,the Xizhe River estuary(S1),Xuanwei City Nuojia Village(S2),Huize County Zhashe Village(S3),Huize County Debai Village(S4),Huize County Niulan were set up The five sampling sections of the River Bridge(S5),the survey content mainly includes plankton species composition,density and biomass,dominant species,biodiversity,and water quality assessment based on physical and chemical factors.The samples collected in this study were fixed on site and brought back to the laboratory of the College of Animal Science of Southwest University for identification and analysis in time.The relevant conclusions of this study are as follows:1.PhytoplanktonSpecies composition:A total of 6 species,8 classes,19 orders,and 100 species were collected.Among them,Bacillariophyta has the most species,with 2 classes,5 orders and49 species;Chlorophyta,followed by 2 classes,7 orders,and 33 species;Cyanophyta,with 1 class and 3 There are 10 species in the order;Englenophyta 1 class,1 order,6orders;the least number of species are Xanthophyta and Pyrrophyta,both in 1 order and1 order.Among the seasonal changes,the total number of phytoplankton species in autumn is 83,and the number of species in winter is 22.The seasons are sorted from fall to fall,summer,spring,and winter.In terms of spatial distribution,there are 80 species in the S1 cross-section,with the most species,and 74 species in the S2 cross-section,with the least species.Specific performance is S1(80 types)>S5(79 types)>S4(76 types)>S3(75 types)>S2(74 types).Density and biomass:The annual average density is 4.42×10⁴ind./L,and the average biomass is 0.018mg/L.Density and biomass are the highest in autumn,the lowest in winter,and greater in spring than summer.The variation ranges are 1.26×10⁴ind./L-5.21×10⁴ind./L and 0.006mg/L-0.027mg/L.The spatial distribution characteristics of density were S1>S4>S2>S3>S5,the spatial distribution characteristics of biomass are S4>S1>S5>S2>S3.Dominant species:including Diatomavulgare,Diatomavulgarevar.Ovalis,Synedraulna,Ceratiumhirundinella,Synedracus,Chlorococcumsp,Chlorellavulgaris,7species.Among them,there are the most diatom phylums,with 4 species.Diatomavulgare,Diatomavulgarevar.Ovalis is the dominant species of the four seasons.Chlorococcumsp and Synedraacus are dominant species in spring and summer,Ceratiumhirundinella and Chlorellavulgaris are dominant species in spring and summer,respectively,and Syndradrana are dominant species in winter.Biodiversity and water quality indicators:H'throughout the year ranges from 2.89-4.22,with an annual average of 3.29;J throughout the year ranges from 0.50-0.75,with an annual average of 0.61;D throughout the year ranges from 3.01-6.01 The annual average is 4.05.The results showed that the spatial distribution pattern of phytoplankton species was uniform and the community structure was relatively stable.According to preliminary judgment,the river section is in a state of light pollution.2.ZooplanktonSpecies composition:51 species of zooplankton were collected.Among them,there are 33 species of Protozoa,the most species;Rotifera is the second,there are 12 species;Cladocera 4 species,Copepoda 2 species.The zooplankton species are the most in autumn,the least in winter,43 in autumn,and 25 in winter.Specifically:Autumn>Summer>Spring>Winter;S1 has the most sections and S4 has the fewest sections,specifically S1(45 types)>S5(41 types)>S3(40 types)>S2(39 types)>S4(38 types).Density and biomass:The annual average density is 975 ind./L,and the average biomass is 0.297 mg/L.The variation ranges of density and biomass were 409ind./L-1507 ind./L and 0.147mg/L-0.452mg/L,respectively.The temporal changes of density and biomass are the highest in autumn,the lowest in winter,and greater in summer than in spring.g.The spatial characteristics of density and biomass are both S1>S4>S2>S3>S5.Dominant species:Difflugia,Tetrahymena pyriformis,Biosminalongirostris,Diaphanosoma,Keratellavalga,Thermocyclops hyalinus.Among them,Biosminalongi-rostris is the dominant species in four seasons,Diaphanosoma shows advantages in spring,summer and winter,Keratellavalga shows advantages in seasons other than winter,Difflugia has advantages in spring and summer,Thermocyclops hyalinus has advantages in autumn,and Tetrahymena pyriformis Summer dominant species.Biodiversity and water quality indicators:the annual average index of H'is 3.57,and the annual variation range is 2.48-4.39;the annual average index of J is 0.60,and the annual variation range is 0.50-0.77;3.77,the annual variation range is 3.02-5.11.The above results show that the spatial distribution pattern of species in this river section is uniform and the water quality is good.The water quality monitoring results of the two sections of the Niulan River Fish Reserve in Qujing City Environmental Protection Bureau for 10 months can be used to determine that the water quality of this river section is in a lightly polluted state.3.Water quality evaluation based on physical and chemical factorsIn the single-factor index method,DO has reached Class I water standards in winter,Class II water in spring,and Class III water in summer and autumn;CODMn meets Class II water standards in all seasons throughout the year;Sampling section.The rest of the seasons have reached Class II water;all sections of NH₃-N winter and spring seasons have generally met Class II water standards.That is,the water quality in spring and winter is better than that in summer and autumn.The Nemero comprehensive index method concludes that the core section of the Niulan River Fish Reserve is in a lightly polluted state.In summary,the spatial distribution pattern of plankton species in the core section of the Niulan River Fish Reserve is even,the community structure is relatively stable,and the water quality is in a lightly polluted state.