Study On Phytoplankton Community Structure Characteristics In The Subalpine Lakes Of Ningwu, North China

In this paper, the phytoplankton community composition, biomass, biodiversity and water quality in Shanxi Ningwu subalpine lakes are investigated and studied from 2007 to 2009. What's more, they are discussed and compared with phytoplankton in other areas.Ningwu subalpine lakes are rare in China. The altitude is from 1771m to 1854m. They have a special geographical location and unique climate characteristics, and have many lakes, complex entertainment, all kinds of water area and very rich phytoplankton resources. There are 291 phytoplankton species or variants belonging to 8 Phyla,10 Classes,23 Orders,45 Families,108 Genus through qualitative and quantitative observation and identification. Bacillariophyta, Chlorophyta and Cyanophyta are dominant Phyla in all lakes, and other phyla are less. However, the species amounts are very different in each lake. The species amount of phytoplankton in mayinghai lake is the most, and the species amount in ganhai lake is the least. Through the statistical of the dominant families, dominant genera and dominant species, it is found that their advantages are very obvious. There are two common dominant families (Fragilariaceae and Naviculaceae) through two methods statistics. There are three dominant genera(Fragilaria, Navicula, Cymbella) and eight dominant species (Aphanocapsa elachista, Microcystis aeruginisa, Phormidium tenue, Cyclotella sp., Fragilaria ulna, Synedra acus, Ankistrodesmus angustus and Chlorella vulgaris).The phytoplankton average cell density of five lakes is 3.49×106 Cells/L in 2009. It is found that phytoplankton species are rich and even, and community structure is stable, and water quality is light-pollution and mid-eutrophic by the analysis of biomass and biodiversity index of phytoplankton in the region. Compared among each lake, the mean cell density of phytoplankton in pipahai lake is the most and Xiaohai lake is the least. Water quality of Gonghai lake is the best and Nuanquangou lake is the most serious.Unlike other several lakes, Nuanquangou lake is an open tourist lake. It is found that the phytoplankton mean cell density in Nuanquangou lake is 2.24×106 Cells/L, and its water quality is light-pollution through the analysis of phytoplankton biomass and biodiversity index. Compared between sampling sites, the phytoplankton average cell density in yacht site is more than Zhihuizhan site, and yacht sites pollution degree is more series. Compared between sampling time, the phytoplankton average cell density in 2009 is more than 2008, and pollution degree in 2009 is more series. Compared between different depths, the phytoplankton average cell density in 0.5m is more than the surface layer.Through comparing with other regions, phytoplankton community structure in Ningwu subalpine lakes is more stable, species much richer and evener, and the dominant species more. The most of phytoplankton community composition in all regions are Bacillariophyta, Chlorophyta and Cyanophyta. The most dominant species in subalpine lakes are diatoms, but the dominant species in plain areas are Cyanophyta and Chlorophyta. The major impact of altitude on phytoplankton is because of the difference of temperature. In addition, the surrounding environment and the physical and chemical indicators are also very important factors.