Research On Characteristics Of The Phytoplankton Community Structure And Its Correlation With Environmental Factors In Zhalong Wetland

Zhalong Wetland is located in the west of Heilongjiang province, the southeast ofQiqihar city, moving downstream from the branches of Nenjiang River, Wuyuer Riverand Shuangyang River. Without clear riverway, it features permanent and seasonallimnetic swampland due to the river overflowing. It was authorized as national naturalconservation area in1987, ranked as international significant wetland directory in1992.As well reserved wetland ecological system in the north of China of the same latitude, itis the most complete, original and open, where a lot of ancient species are preservedperfectly in the natural gene pool and it is one of the ideal perching and growing placefor migratory birds and precious waterfowl. According to the type of land utilizationand the feature of ecological environment in Zhalong wetland, a comprehensive andsystematic investigation has been made for spatial distribution of phytoplanktoncommunity structure of Zhalong Wetland, using the traditional analysis method onphytoplankton and multivariate statistics to analyze the impact on phytoplanktondistribution with physicochemical index and the response to environmental factors.Meanwhile, geostatistics and Monte-Carlo methods have been used to estimate spatialdistribution and forecast health risk of the heavy metal content in the surface water ofZhalong Wetland. Aiming to offer phytoplankton information and reference for theresearch on Zhalong Wetland aquatic ecosystem, a method of combining phytoplanktonand physiochemical index has been applied to assess water nutrition status in ZhalongWetland provides scientific reference for a further study on the sustainability, protectionand establishment of management measures of wetland living resources and which, isvery valuable to early warning of the aquatic eutrophication in Zhalong Wetland.After the investigation of phytoplankton community structure in Zhalong Wetland,it is found that there are a wide range of phytoplankton and complicated communitycomposition in this area. In the paper, there are354phytoplankton taxa being identifiedwith6divisions,8classes,21orders,33families80genera wherein Chlorophyta11families,36genera,148species, Bacillariophyta10families,24genera,119species,Cyanophyta6families11genera45species, Euglenophyta2families,5genera,38 species, Pyrroptata3families,3genera,3species, Chrysophyta1family,1genus,1species. It reveals in the quantitative analysis result that the average cell density ofphytoplankton is12.71x106L-1, wherein Bacillariophyta takes up49.6%as the largestcell density, Chlorophyta and Cyanophyta taking the second and the third placerespectively26.2%and15.0%with obvious spatial change. Discharge area(17.51×106L-1)＞experimental area(12.66×106L-1)＞buffer zone(11.92×106L-1)＞corearea(11.14×106L-1). The dominant species include Cyclotell meneghiniana, Chlorellavulgaris, Trachelomonas volvocina and Nitzschia.The environmental factors in Zhalong Wetland have been analyzed based on themethod of principal component analysis. The first two ordination axes explain73.2%according to the physicochemical factors to the environmental variation. By theexample correspondence analysis, the7environmental variations, namely, total nitrogen,total phosphorus, potassium permanganate index, conductivity rate, pH value, turbidityand chlorophyll a, explain50.2%to species data, and characteristic value is0.464and0.343respectively. Total phosphorus, conductivity rate and pH value have a big impacton species distribution of phytoplankton, whereas some respond distinctively toenvironmental variation, namely, Cyclotella meneghiniana, Cymbella cistula,Asterionella formosa, Chlorella vulgaris and Trachelomonas volvocina.The analysis on spatial distribution of heavy metal concentration of the surfacewater in Zhalong Wetland by means of geography statistics method and on thecorrelation among heavy metals determines the source of heavy metal, including3origins: first, industrial and living pollution, such as farm products processing,paper-making industry, domestic wastewater and domestic waste discharge, such asfeces and cells; second, organic fertilizer pollution, such as pesticide and chemicalfertilizer; third, traffic pollution, such as traffic emission. Based on Monte-Carloanalysis on the sensitivity of heavy metals in the surface water, it is concluded that Crconcentration should be controlled to lower the carcinogenic risk to human being. It canalso be concluded through data analysis and health risk forecast that the carncinogenicrisk in Zhalong Wetland is lower than the maximum acceptable annual risk level,5.0×10-5, and lifetime acceptable risk level,3.5×10-3, recommended by ICRP.The water status in Zhalong Wetland has been comprehensively assessed by meansof phytoplankton cell density, diversity index, biological indicator and comprehensive nutrition status index. The data of phytoplankton, in which cell density is7×106～27.9×106, oligotrophic status11.1%, mesotrophic status88.9%, manifests that the waterin Zhalong Wetland belongs to mesotrophic status. In light of the diversity ofphytoplankton, Shannon-Weaver diversity index lies between1.26and2.96, Margalefdiversity index between0.79and3.47, in which the oligotrophic status takes up2%,slight contamination type32%, moderate contamination type56%, heavy contamination10%. The data shows that most of the Zhalong water belongs to moderatecontamination type. Indicated species of α-moderate contamination area and β-moderatecontamination area take majority amount in phytoplankton of Zhalong Wetland. In linewith comprehensive nutrition status index, in Zhalong Wetland mesotrophic takes up53.9%, eutrophy47.1%. The mesotrophic status takes a majority part in thecomprehensive nutrition index and the water stays in a moderate contamination status.