Evaluation Of Water Quality And The Type Of Nourishment In The East-half Of Lake Chaohu By Means Of Plankton

The paper was based on the unified relation between biology and the environment,and used the plankton to evaluate water environment.Sampling water was get from the east-half of Lake Chaohu and the basic characteristic of plankton including the community structure,predominant species' composition,quantity of the plankton and their seasonal change were studied every month from June,2005 to February,2007.The content of primary productive forces chlorophylla,the trophic state index(TSIm),ratio of alga,alga saprobic index,Shannon-Wiener biodiversity index and Evenness Index of phytoplankton,Margalef biodiversity index of zooplankton and Rotifera,index of B/T,E/O,ferlity of zooplankton and saprobic system index to evaluate the water quality and the type of nourishment of the east-half of Lake Chaohu.The experiment data was provided for the government of nourishment of the east-half of Lake Chaohu,and a method and mentality was provided for the study of ecology of community structure of plankton.Two-hundred and eight species of phytoplankton were found,belonging to ninety-five categories,of which senventy-three species were Chlorophyta(35.27%), fifty species were Cyanophyta(28.02%).The predominant phytoplankton communities were Cyanophyta and Chlorophyta.The predominant specises were mainly Pediastrum integrum,Ankistrodesmus,Ankistrodesmus falcatus and Microcystis aeruginisa,Anabaena flos-aquae,Nostoc planctonicum,Anabaena spiroides,Melosira granulata var angustissima and Navicula pupula var.aspitata, Cymella tumida,Peridinium bipes,Microcystis aeruginisa and Pediastrum integrum. Microcystis aeruginisa and Pediastrum integrum were appeared every season.They were common species.The quanity of phytoplankton and the content of chlorophylla were very high in summer and autumn and were very low in spring and winter.The average quantity of phytoplankton was 5.28×10⁶ ind·L^-1during the study time.The highest quantity of phytoplankton was 1.92×10⁷ind·L^-1in July,2005,and the lowest quantity of phytoplankton was 3.9×10⁵ind·L^-1in Feburary,2006.Abount zoonplankton,two-hundred species were found,of which eighty-one species were Protozoa(40.50%),sixty species were Rotifera(30.00%),thirty-three species were Cladocera(17.00%)and twenty-six species were Copepoda(13.00%). The predominant specises were mainly Hexamita inflate,Cochiopodium minutum, Difflugia corona,Walich Lecane niothis,Trichocerca bicristata,Keratella quadrata, Diphanosoma brachyurum,Bosmina fatulis,Burckhardt,Bosmina longirostris and Limnoithoma sinesis.The predominant zooplankton communities were Protozoa and Rotifera.In conclusion,the change of quantity of zooplankton was great compared to their species,the average quantity of zooplankton was 4.10×10³ ind·L^-1during the study time,the highest quantity of zooplankton was 9.77×10³ ind·L^-1in June,2005,the lowest quantity of phytoplankton was 916.00 ind·L^-1in Januery,2007.For the growth temperature of the zooplankton were different,their seasonal variation were different. In summer and autumn the quanity of Protozoa and Rotifera were higher,however in spring and winter their quanity and species were very low.Cladocera and Copepoda were appeared every season,in spring and winter they were mainly young individual, in spring and autumn they were mainly adult individual especially in spring the quantity of Cladocera and Copepoda were higher.The results of using the content of primary productive force chlorophylla,the trophic state index(TSIm),ratio of alga species of phytoplankton,the index of B/T, E/O and ferlity of zooplankton to evaluate the type of nourishment of the east-half of Lake Chaohu were consistent.The water of the east-half of Lake Chaohu was in the state of eutrophication,the degree of the eutrophication was light in spring and winter and was heavy in summer and autumn.The results of using the alga saprobic index,Shannon-Wiener biodiversity index, Evenness Index of phytoplankton,Margalef biodiversity index of zooplankton and Rotifera and saprobic system index to evaluate the water quality of the east-half of Lake Chaohu were consistent too.The east-half of Lake Chaohu Lake was polluted and was in the state of mesosaprobic zone.The degree of pollution was varied with the season.The degree of the pollution was light in spring and winter and was heavy in summer and autumn.