Studies On The Variation Of Periphytic Algal Communties And Biomass In Jinyang Lake

The purpose of this study was to provide scientific basis for protecting the ecological environment of Jinyang Lake waters while developing the economy,and to further the development and adoption of practical,concrete and effective measures in order to control water quality deterioration by the primary research of the spatial and temporal changes of species composition, diversity,biomass and community structure of periphytic algae in Jinyang Lake,as well as the relationship of the environmental factors and the biomass & community structure during one year beyond Jinyang Lake shore.The author sampled in Jinyang Lake on the 9th of each month from March 2006 to February 2007,and measured environmental factors, periphytic algal species composition and biomass of each sampling spot. After the investigation and research in a year,227 species of periphytic algaes(including variants),under the membership of 3 divisions,27 families, 62 genera,were found.Among them,Bacillariophyta was the dominant division,a total of 164 species of 24 genera;then it was followed by Cyanophyta,49 species of 25 genera;Chlorophyta was the least one,a total of 14 species of 13 genera.The temporal and spatial variation of periphytic algae species composition was showed obviously.The number of species was dominant in summer,followed by winter,spring and autumn.At theⅢsampling spot the maximum number of species was found,followed byⅣ,Ⅰ,Ⅱ.At the same time,periphytic algae species composition of the Shannon-Weaver,Margalef and Simpson diversity index showed obvious temporal and spatial variation.The descending sequence of diversity index of sampling spots in spring wasⅣ＞Ⅰ＞Ⅱ＞Ⅲ;in summerⅢ&Ⅰ＞Ⅱ＞Ⅳ;in autumnⅠ＞Ⅲ＞Ⅳ&Ⅱ;in winterⅢ＞Ⅳ＞Ⅰ＞Ⅱ.According to evenness index changes,there was the highest eveness of community structure of periphytic algae at sampling spotⅠin Jinyang Lake in spring,summer and autumn.But in winter,the highest eveness was in sampling spotⅢwhile the lowest eveness was in sampling spotⅠ.In this paper,Cluster and Non-matric Multi-Dimentional Scaling(MDS) methods were also used respectively to do multivariate statistical analysis of the seasonal changes of community structure of periphytic algae.The community structure of periphytic algae in the different sampling spots were found to be greatly different.Principal Component Analysis(PCA) method was used to analyze five indexes of the environment(water temperature,air temperature,dissolved oxygen,pH,conductivity) in each sampling spot. Their effects to community distribution showed that,the water temperature was most closely related to taxis axis in every season.It meaned that the distribution of periphytic algae community was mainly affected by water temperature,and other environmental factors had weaker effects.Furthermore,the average biomass of periphytic algae was gradually reducing in different seasons.The annual average biomass reached its peak in summer,lower in autumn,and at the lowest level in winter.The reducing rate sequence of the sampling spots wasⅢ,Ⅰ,Ⅱ,Ⅳ.Moreover,the biomass change was mainly affected by water temperature,and it increased along with the increase of water temperature in a certain range.Finally,saprobic system method and dominant population method were used to evaluate the water quality of Jinyang Lake.The results showed that the water quality of Jinyang Lake was close to mesosaprobic type which is typical in a Nutritious-type alkaline lakes.According to Bacillariophyta biological index,the water quality of sampling spotⅢwas the best,but the water quality of sampling spotⅣwas the worst and had been polluted.The nutrition level of the lake decreased from spring to winter.In winter the water nutrition level was the minimum,but in spring the water had the highest nutrition level.In addition,this paper also analyzed the reasons for the eutrophication of water,and put forward preventive measures.