Study On The Phytoplankton And Water Quality Of Main Closed Water Bodies In Central Urban Area Of Hefei City

Abstract:Planktonic algae,as an important biological indicator of water quality monitoring and water environment protection,has different community composition,structure and distribution characteristics.This research mainly makes study on the phytoplankton community ecological of the mainly closed water bodies of Hefei central city?Dong Pu Reservoir,Dafangying Reservoir,Swan Lake,Emerald Lake and Ring River?.The water quality comprehensive evaluation and eutrophication evaluation of the main closed water bodies in the central city of Hefei were analyzed by using the temporal and spatial characteristics of phytoplankton community composition,combined with the analysis of physical and chemical factors of water quality.This survey provides a reasonable and effective management and water environment protection for closed water bodies in Hefei central city.From July in 2015 to August in 2017,we set 30 sampling points on the five main closed water bodies in the central urban area of Hefei,The species composition,density change,dominant algae,chlorophyll a content and chlorophyll content Fluorescence parameters such as TN?NH₃-N?TP?COD_cr?ORP?DO?Fm/Fv?WT and pH values were measured and analyzed.The results are as follows:?1?The analysis of the temporal and spatial characteristics of water quality factors shows that Dongpu Reservoir,Dafangying Reservoir and Swan Lake are generally polluted with the overall water quality reach"The national environmental quality standard of surface water"?GB3838-2002?II^III standard.But the Emerald Lake and Ring River water pollution is serious,especially for Ring River pollution extremely seriously,kthe main water quality indicators are more than?standard;According to the effect of N:P ratio on the phytoplankton,the five closed water bodies are phosphorus limited condition.?2?The algae microbes in closed water bodies were studied and analyzed.The results showed that the five water bodies in the central urban area of Hefei had higher biological diversity,among which the Ring River water and Dafangying Reservoir were the most abundant.There are also differences in the dominant species in different closed water bodies.The Bacillus proteus?Thalassiosira and Gonium are dominant species in Dongpu Reservoir.The Zoogloea occupies an absolute advantage in the Dafangying Reservoir.The dominant species in Swan Lake are Polynucleobacter acidiphobus sp.and Denitratisoma sp.The Zoogloea sp.in the Emerald Lake water body occupies an absolute advantage.The bacteria in the water bodies are the same and different,which reflects the high biological diversity of the algae microbes in the enclosed water bodies in the central urban area of Hefei.?3?During July in 2015 to August in 2017,it were identified of totally plankonic alage of 7 species,139 genera and 386 species?including varieties and variants?.Among them,the Chlorophyta is the most;the Bacillariophyceae and the Cyanophyta are second;the Chrysophyta?Pyrrophyta?Euglenophyta and Cryptophyta species are less,and the quantity of them is more stable.The dominant species mainly composed by Pediastrum?Scenedesmus?Closterium?Ankistrodesmus sp.?Selenastrum?Golenkinia?Crucigenia and Oocystis of Chlorophyta,Synedra?Nitzschia?Melosira?Cymbella?Navicula?Fragilaria?Stauroneis and Cyclotella of Bacillariophyta,Aphanizomenon?Pseudanabaena?M.aeruginosa?Oscillatoria?Anabaena and Merismopedia of Cyanophyta,Euglena?Trachelomonas and Phacus of Euglenophyta,Gymnodinium?Glenodinium and Ceratium of Pyrrophyta,Dinobryon and Synura of Chrysophyta,Cryptomonas and Chroomonas of Cryptophyta.Among them,Pediastrum of Chlorophyta and Synedra of Bacillariophyta were the main dominant species during the investigation period.The dominant species of algae in different time and different points of the composition are also different from the point of view.The number of species is more in summer and autumn,but less in winter and spring.The distribution characteristics of phytoplankton species number is Ring River>Emerald Lake>Swan Lake>Dongpu Reservoir>Dafangying Reservoir.?4?During the investigation,the survey of the proportion of planktonic algae density in different sampling times shows that the density of phytoplankton is mainly composed by Chlorophyta?Bacillariophyta and Cyanophyta,and Chlorophyta>Bacillariophyta>Cyanophyta;The overall trend of phytoplankton density in the main closed water bodies in the central urban area of Hefei is the autumn in 2015>the summer in 2015>the autumn in 2016>the summer in 2017>the spring in 2017>the spring in 2016>the winter in 2016.Totally it shows that autumn>summer>spring>winter and year of2015>year of 2017>year of 2016.So it can be concluded that the average density of phytoplankton in the main closed water bodies in the central urban area of Hefei shows a more obvious seasonal variation.The suvey of the average density of phytoplankton in the main closed water bodies in the central urban area of Hefei show that the average density of phytoplankton in five closed water bodies is 29.38×10⁶ cell/L.The magnitude of the change is the Ring River,the maximum is 17.7 times the minimum value.The average density of planktonic algae in the central urban area of Hefei is:Ring River>Emerald Lake>Dafang Ying Reservoir>Dongpu Reservoir>Swan Lake,the trend is basically consistent with the spatial distribution of phytoplankton species.?5?The average content of chlorophyll-a in the closed water body of Hefei central city is in the range of 15.834⁵8.658?g/L,the summer and autumn season is higher and the winter and spring season is lower,which is consistent with the change of species and density of phytoplankton.The temporal variation of chlorophyll-a content in green algae,diatoms and cyanobacteria was consistent with the total chlorophyll-a content.The content of chlorophyll-a in diatoms was decreased with the increase of seasons,and the change of chlorophyll-a content in diatoms decreased with the increase of seasons.In general,diatoms and cyanobacteria showed a trend of increasing by years.The growth potential of phytoplankton in closed water bodies varies with the seasons.In the winter and spring months,the Fv/Fm ratio is relatively small,that is,the potential maximum photosynthetic capacity of the phytoplankton is weak,and the Fv/Fm ratio is larger in the summer and autumn seasons.The maximum photosynthetic capacity of the planktonic algae is compared:Ring River>Emerald Lake>Swan Lake>Dongpu Reservoir>Dafangying Reservoir.?6?The change of water quality factor has some correlation with phytoplankton community structure.The results of analysis of correlation betweeen water quality factors and phytoplankton using SPSS20.0 software shows that the water quality factors had some effects on the phytoplankton community in the closed water bodies of the central urban area of Hefei are mainly the DO?WT?TN?NH₃-N and TSS,but the CODcr?TP and pH value have little effect on phytoplankton.Among them,DO and WT mainly affected the phytoplankton community by influencing the species and density of phytoplankton,but there was no significant correlation between CODcr and the phytoplankton community characteristic index,but promoted the density of phytoplankton in summer and autumn,TN and NH₃-N promoted the density of phytoplankton in winter and spring,and TP promoted the species and density of phytoplankton in summer and autumn.?7?By comparing four analytical models,the analysis shows that the main closed water bodies in downtown of Hefei have been in a state of nourishment.Pollution index evaluation shows that the Dongpu Reservoir,Dafangtiao Reservoir and Swan Lake are mildly eutrophic while Emerald Lake and the Ring River are moderately eutrophic and have the tendency to change to the state of heavy eutrophication.Diversity index evaluation method shows that the five water bodies are in a moderately eutrophic state as a whole with a gradual increase tendency.The analysis of the dominant species can determine that the five water bodies are eutrophic water bodies,and the relevant weighted comprehensive nutritional status index method shows that the five water bodies are in a moderately rich Nutritional status.The comprehensive analysis shows that the main closed water bodies in the central urban area of Hefei have been in an eutrophic state with a tendency of aggravating.