The Three Gorges Reservoir, located at 29 degrees 16'-31 degrees 25'N and 106 degrees 50'-110 degrees 50'E,is the largest water conservancy for irrigation works and generate electricity in China. It has a total area of 54061.5km(2) and a water area of 189km(2), when the normal pool level is 175m. In order to understand the diversifications and effects of sluice on water environment and aquatic ecosystem, the authors made a preliminary study on the phytoplankton features, including species richness, dominant species,cells and diversity index, in the Hubei river section of the Three Gorges Reservoir during the period before sluice (2002. 12-2003. 06) and after sluice(2003. 06-2004. 05). The results showed that the species richness, composition and cell densities of algae were changed considerably throughout the studied period. Before sluice, in total of 79 species of algae were observed, belong to 7 phyla and 66 genera. Diatoms,green algae and blue-green algae occupied 34.6% 38.5% and 10.3% of the total, respectively. Other four phyla were only representing 16.6%. After sluice, the species richness of algae were increased to 151 species, belong to 8 phyla and 103 genera. The percentage of diatoms,green algae and blue-green algae was 23.8%, 55.0% and 9.9% to the algae flora, respectively. The species richness of diatoms was decreased,but that of green algae was increased. The cell densities of algae were the following situation: Before sluice, the monthly mean values were reached to 272.6 x 10(4) ind./L in the main channel, and to 1042 x 10(4) ind./L in the bay region. After sluice, the values were raised to 384.8 x 10(4)ind./L and 2006.7 x 10(4)ind./L, respectively, increased by 41.2% and 92.6% than that before sluice. The concentrations of nitrogen and phosphorus were in the range of 2.39-2.54mg/L and 0.11-0.18mg/L in the main channel, and 1.42-1.84 mg/L and 0.18-0.30mg/L in the bay region, respectively. Those were much higher than the values in normal water bodies. The trophic status of the studied river section is at mesotrophy level in the main channel and at alpha-beta-mesotrophy level in the bay region. The results illuminated that the process of valley changing into reservoir would be surely to affect the ecological characteristics of algae in aquatic ecosystem. Therein I the effects were more notably on bay region. Some prevention and cure measures and advices were also given in the paper, for protecting the water quality of the Three Gorges Reservoir.
Kuang Qi-jun; Bi Yong-Hong; Zhou Guang-Jie; Cai Qin-Hua; Hu Zheng-Yu (Huzy@ihb.ac.cn).Study on the phytoplankton in the three gorges reservoir before and after sluice and the protection of water quality,Acta Hydrobiologica Sinica,2005,29(4):353-358
