The Spatio-temporal Variation Of Phytoplankton Community And Size-fractionated Chlorophyll-a In Baiyangdian Lake

As the largest inland freshwater lake in the North China, Baiyangdian lake plays an irreplaceable role in the ecological health and environmental safety. In the recent twenty years Baiyangdian lake has been contaminated seriously, its restoration is becoming a top priority. Succession of phytoplankton community is basic to improve the eutrophication of Baiyangdian lake. In the paper, Eight typical sites was selected in April, July, September and November in 2010, in order to investigate the structure of phytoplankton community and the state of environment and analyse the relationship of size-fractionated Chlorophyll-a contents and environmental factors, which can provide the theoretical basis for improving eutrophication of Baiyangdian lake. The results were followed as:1 The physical and chemical factors of Baiyangdian lake had temporal and spatial heterogeneity. Using five indicators to calculate the TLI, except Caiputai in spring and winter and Guangdian, Wangjiazhai in spring, the other sites were all in the eutrophic state. Pollution of Baiyandian lake was characterized by COD_Mn,BOD₅,TN and TP by principal component analysis.2 The phytoplankton community in Baiyangdian Lake was composed of 8 Phylums and 183 species（genus）. Chlorophyta represented 37.70% of total species, which had 69 species. Bacillariophyta represented 20.80% of total species, which had 38 species. Cyanophyta represented 18.00% of total species, which had 33 species. Euglenophyta represented 12.60% of total species, which had 23 species. Pyrrophyta represented 4.40% of total species, which had 8 species. Chrysophyta represented 2.70% of total species, which had 5 species. Xanthophyta represented 2.20% of total species, which had 4 species. Chrysophyta represented1.60% of total species, which had 3 species. Phytoplankton species in Baiyangdian lake were dominanted by Chlorophyta and Cyanophyta.3 Size-fractionated Chlorophyll-a of phytoplanktons and water quality variables were investigated in Baiyangdian lake. Results showed that Chlorophyll-a concentration of net-phytoplankton and nano-phytoplankton were main contributors to the anual mean of Chlorophyll-a in Baiyangdian lake, accounting for 83.76% together,which indicated Baiyangdian lake had been a more nutrientive water body. Seasonal variations of percentage of all size-fractionated Chlorophyll-a were closely related to seasonal succession of phytoplankton community structure. Percentage of net-phytoplankton Chlorophyll-a peaked in winter, nano-phytoplankton Chlorophyll-a peaked in spring and winter while that of ultra-, pico-phytoplankton peaked in summer. Bivariate correlation analysis showed that percentage of net-phytoplankton Chlorophyll-a was positively correlated with TN/TP, temperature and CODMn, While that of ultra-, pico-phytoplankton was positively correlated with temperature significantly, which showed that larger sized phytoplankton had closely relationship with the contaminative degree of Baiyangdian lake. Net-phytoplankton and nano-phytoplankton were the main contributors of phytoplankton in Baiyangdian lake. Correspondingly, the non-classic biomanipulation on the basis of feeding habits of aquatic animals such as filtering fish was proposed to control eutrophication of Baiyangdian lake.