Abstract:

During the first experimental storing water to 175 m (elevation) in the Three Gorges from January to March in 2009，the investigation on the  activities of diatom in the outlet of the Jialing River in spring had been studied，then the effects on diatoms had been analysed through diatom changes in the spring of 2007 and 2009.The results showed that，compared with 2007，the water level in the outlet of the Jialing River increased 254~784 m in 2009，the velocity decreased 001~005 m/s，PO3-4 decreased to 0018~0049 mg/L，and NO-3 became lower (106~155 mg/L).There were 78 species of diatom and 6 dominant species of diatom，and the density of algal was 900×104~11140×104 cells/L in 2007；while there were 91 species of diatom and 10 dominant species of diatom in 2009，and the density of algal was 097×104~7064×104 cells/L.The composition of diatoms mainly included 〖WTBX〗Navicula,Fragilaria,Gomphonema,Synedra,Melosira〖WTBZ〗 and 〖WTBX〗Cymbella〖WTBZ〗，and the composition had little change in 2007 and 2009.〖WTBX〗Cyclotella asterocostata〖WTBZ〗 is water bloom species.Through the analysis，we found that the water level in the outlet of the Jialing River and the species of diatoms increased，and the velocity，nutrient and the density of diatoms decreased，the composition of diatoms had little change，and 〖WTBX〗Cyclotella asterocostata〖WTBZ〗 was more outstanding during storing water to 175 m in the Three Gorges.〖