A Comparative Study On Seasonal Variation Characteristics Of Planktonic Diatoms In Typical Urban Lakes And Natural Lakes

This subject is aimed to use the principal component analysis to compare analyse the environment index of typical urban lakes-Dongchang Lake and natural lakes-Dongping Lake, and prove the environmental factors which palys a leading role in the water quality. Then use corrected Carlson Nutrition State Index Method to analyse the nutritional status of Dongchang Lake and Dongping Lake, combined with the diatoms combination's indication to the lake eutrophication. And redundancy analysis to analyse the relationship between diatoms species and water environment of two types lakes, and revealed the seasonal variation characteristics of planktonic diatoms of two types lakes, providing theoretical basis for the environment restoration and governance of urban lakes and natural lakes. Main conclusions are as follows:1. From the point of water quality condition, there is difference between the water quality of two type lakes. The water quality level of Dongping Lake during four quarters is higher. The lake water in Summer belongs to ?type, whose quality is the worst. The water quality of other three seasons is slightly better. Using corrected Carlson Nutrition State Index Method proved that the nutrition level of Dongping lake is middle- rich nutrition level. The water quality of Dongchang lake in August and October is the worst, belonging to ?type. and the water quality in December and January is the best, belonging to?type and?type respectively. Using corrected Carlson Nutrition State Index Method, the nutrition level of Dongchang Lake is middle nutrition level.2. There is spatial distribution difference between Planktonic diatom community of two types lakes.Spatial distribution of planktonic diatom community can be divided into five types,Planktonic Aulacoseira granulateis the dominant species in the I and ?type, In the type, the most obvious difference is ? Thalassipsira baltica contents, significantly higher than other four types contents of this kind. In the ? type, Aulacoseira alpigena contents is the highest in all sample points. Planktonic diatomAulacoseira granulate as the dominant species in the ? type. Achnathes minutissima is the dominant species in the four sample points of Dongchang lake. But there is difference spatial distribution in different sample points. Nitzschia palea ?Cyclotella meneghiniana?C.pseudostellig?Cyclostephanos invistatus?Aulacoseira granulata?Aulacoseira alpigena and other species is higher in the east bridge than other sites.Nitzschia palea?Cyclotella meneghiniana?Cyclostephanos invistatus?Aulacoseira granulata?Aulacoseira alpigenaand other species is lower in the west bridge than other sites, epiphytic benthic species is dominate in this sample, it have the lowest water level and best water quality; Fragilaria nanana increased obviously in south and noth bridge, so the water quality is a bit better than east brige.3. There is obvious difference between the significant environmental factors that influence the change of planktonic diatom combination of two types lakes. Chla?pH?TP are significant environmental factors that influence the change of planktonic diatom combination in Dongping lake. The eutrophic half planktonic floating Aulacoseira granulata is the dominant species of the planktonic diatoms in Dongping lake, making Dongping Lake close to the eutrophic state. The planktonic diatom of Dongping Lake presents good seasonal succession. Aulacoseira alpigena is the dominant species in spring. Aulacoseira granulata is the dominant species in summer, suggesting that the lake in summer still in eutrophic state. Aulacoseira alpigena is the dominant species in autumn Fragilaria capucina is the dominant species in winter. In Dongchang Lake environmental factors,transparency is the significant environmental factors that infuence the change of planktonic diatom combination of Dongchang Lake. Looking from the combination distribution, Achnathes minutissima and F.construens var venterappear throughout the year with a larger proportion. But the diatoms species also shows a better seasonal succession.When the total phosphorus concentration of Dongchang Lake is high inJuly ? August and September, the proportion of Achnathes minutissimaisdecreased significantly, When the total phosphorus concentration in March?May?November and December is lower, the proportion of this species makeing it becoming the most dominant species. Achnathes minutissima requires much about transparency level of the environment, so it is positively correlated with transparency level. Transparency inwinter and spring was obviously higher than that in summer and autumn, whilecoinciding with the seasonal distribution of Achnathes minutissima.In general, the city lake represented by Dongchang Lake and the natural lake represented Dongping Lake all have worse water quality and higher nutrition level in summer, and at this time, the proportion of eutrophic planktonic diatoms is bigger. In winter, the water quality of two lakes is better and the nutrition level of two lakes is lower, then there is a larger proportion of epiphytic benthic diatoms. The region that contaminated serious and rich nutrition area indicated by diatoms of two lakes is mainly due to human's activities. There is spatial distribution difference in Planktonic diatom community of the two lakes. The area concentrated by rich-nutritational species close to the region contaminated serious by human's activities. In Dongping Lake environmental factors, Chla?pH?TP are significant environmental factors that influence the change of planktonic diatom combination in Dongping lake, which in Dongchang Lake environmental factors,transparency is the significant environmental factors that infuence the change of planktonic diatom combination of Dongchang Lake, explaining the water quality of Dongchang Lake better than the water quality of Dongping Lake. The water quality of Dongchang Lake is better, on account of the unified management of water environment and the prevention of the source of pollution, which Dongping Lake lack protection and governance, so the lake was polluted more serions. Hope that more experts and scholars focus on the management of natural lakes.