Research On Phytoplankton Community Of Eutrophic Lake In Different Cascading Trophication

From the viewpoint of ecology, the unity of biology and the environment is the result of interaction with each other, water envrionment determines the characteristics of biology populations and community structure, on the contrary, the biology entity, population or community can objectively reflect the changes of the waterbody quality.therefore, It is important to study the species composition, the dominant species, the biomass and the relative frequency of the primary producers—phytoplankton, It is also important to the development and use of lake resources rationaly and the prevention of eutrophication.The ecological study of phytoplankton was conducted on four typical sampling stations in Guanqiao lake during August and October two thousand seven, April two thousand eight and Ziyang lake during April two thousand eight. All the samplings were carried on qualitative and quantitative analysis in laboratory. Meanwhile, some physical and chemical indices, for example, WT, SD, TP, TN, NH3-N, COD, and so on, were measured on local or in laboratory. Phytoplankton communities and biodiversity were examined by multivariate analysis. The correlation between phytoplankton and environment was determined by correlation analysis. The paper provided referenced evidence for the control of lake eutrophication and the reasonable production of the fishery.Total of 5 phyla 63 species and 6 phyla 81 were identified in Guanqiao lake and Ziyang lake, respectively. The changes of the number and species of phytoplankton were very significant with the time, the species of algae were in the spring (April) and summer (August), it was relative low in the Autumn (October) in Guanqiao lake, and the phytoplankton species in Ziyang lake were more than Guanqiao lake, Chlorophyta and Cyanophyta were the dominant species in April.The phytoplankton community structure of Guanqiao Lake relative simple, the the relative frequency of typical kind of eutrophication in Guanqiao Lake was higher than Ziyang lake in April. It showed that Guanqiao Lake was more healthy than Ziyang lake, However, we can see that the health was relative from the two communities similarity.correlation analysis showed that the phytoplankton of two lakes was positive relevant to TN, TP and WT and negative relevant to SD, The chlorophyll a changed in the range of 45.01-110.12μg·L^-1 in Guanqiao Lake and 16.05-84.41μg·L^-1 in Ziyang lake, It showed that the two lakes were eutrophic lakes, The chlorophyll a of Guanqiao lake was more than Ziyang lake, it showed that the eutrophication of Guanqiao lake was more serious than Ziyang lake in April.