Status Of Phytoplankton In Jinyang Lake And Its Eutrophication Evaluation

Jinyang Lake locats in Taiyuan city, Shanxi province, North China. There is three kilometers from the urban district. The south of Jinyang Lake is Ancient City of Jinyang which has a long history and Jinci Temple renowned in China and world, while on the east and west are Jinci Road and Taiyuan No.1 Thermal Power Plant. Its total area is nearly 5.26 square kilometers and the water area is 4.8 square kilometers. Jinyang Lake is the largest artificial lake in the north China. The average water depth is 4 meters and the deepest place is 8 meters. In summer, the average maximum water temperature reaches 33℃ and the temperature is 5-15℃ in winter. The water does not ice up perennially (party of the water ices up occasionally). It has several functions such as electricity generation, pisciculture, traveling and so on. The purpose of this paper is evaluating the Jinyang Lake water quality and the development tendency from biological view, through researching seasonal variation of phytoplankton community structure in Jinyang Lake combined with physical and chemical factors, in order to propose the scientific foundation for protecting the water ecological environment with economy development, furthermore, taking the practical, feasible and effective measures to control the water quality.From September, 2004 to August, 2005, collecting specimens of phytoplankton once a month in Jinyang Lake, at the same time watertemperature, air temperature, transparency (SD), dissolved oxygen (DO), pH, conductivity in every sampling site are measured separately. Through identifying specimens, phytoplankton is discovered 167 species (including varieties) in total and they belong to 5 divisions, 25 families and 57 genera. Among them, Chlorophyta is the most, 61 species, which belong to 29 genera, next is Bacillariophyta, including 40 species, belonging to 17 genera, the third are Cyanophyta and Euglenophyta, 33 species and 31 species separately, which belong to 15 genera and 5 genera, Charophyta includes the least, only 1 genera, 2 species.Phytoplankton composition has obvious seasonal characteristic. In autumn, species are the most, spring less and winter the least. Furthermore, in every season, Chlorophyta includes the most species, Cyanophyta and Bacillariophyta less. Different sampling site has different phytoplankton distribution. In No.l sampling site, species are the most, No.2 sampling site has least, No.3 sampling site> No.4 sampling site> No.5 sampling site have nearly the same number and No.5 sampling site has much more. In every sampling site, Chlorophyta is the most, next are Cyanophyta and Bacillariophyta, Charophyta is few. Different sampling site even the same sampling site in different season, its dominant species is also different. In No.2 sampling site, Cyanophyta is the dominant community, In Nol sampling site, No.3 sampling site, No.4 sampling site, No.5 sampling site, their dominant community are Cyanophyta, Chlorophyta and Bacillariophyta.Oscillatoria amphibian Ag. is the dominant species in each sampling site in spring. Anabaena azotica Ley is the dominant species in each sampling site in summer. Dominant species are the most in autumn, less in spring, least in winter. Cell density of Cyanophyta is the most, Chlorophyta and Bacillariophyta are next and others are correspondingly less. Cell density of No.l sampling site is highest, next are No.3 sampling site and No.4 sampling site, cell density of No.2 sampling site is lowest. Generally speaking, cell density of phytoplankton in water surface is more than which in 0.5 meter under water surface. Using four eutrophication biological evaluation methods —Saprobic system, Bacillariophyta Index, Trophic Index and Phytoplankton community analysis, we classify the trophic status of Jinyang Lake, which is now a light- eutrophication water body and the water quality is closed to ￡ — mesosaplobic. At last, protective and managing strategy are suggested for water quality of Jinyang Lake.