Phytoplankton In Yangtze And Three Gorges Reservoir: Dynamics And Relationship With Nutrients And Hydrological Conditions

The environmental problems caused by large-scale water conservancy on aquatic ecosystem have become the focus of the world. As the largest water conservancy in the world, Three Gorge Project (TGP) will have a far-reaching impact on the ecosystems in the Yangtze River, the estuary and the nearby coastal area, especially on the biodiversity due to the changes resulted from the geochemical cycle of bioactive elements. However, as a country with the most dams in the world, reseach in river phytoplankton ecology in China have been relatively rare and lag behind the trend in the area. This thesis focues on the dynamics of the phytoplankton in TGR and the Yangtze as well as in the Han River and seeks to find the relationship between the dynamics of phytoplankton and main environmental parameters such as hydrological condition, nutrients, temperature, etc.., Following studies have been conducted: 1) Composition and abundance of the phytoplankton and eutrophication in the Three Gorge Reservoir (TGR) after impoundment; 2) Relationships between algae, nutrients and hydrological conditions in the Yangtze and TGR ; 3) Annual variations of the algal composition and abundance in the down reach of Han River (Wuhan reach), the largest anabranch in the middle reach of the Yangtze; 4) Influence of water current on the composition and abundance of phytoplankton; 5) Influence of temperature on the composition and growth of algae. The results are summarized as below:1) Surveys were performed during July 2004 to August 2004 (rainy season) and April 2005 (dry season). Along 6 transects with 23 stations, 314 samples had been collected. Algal biomass has increased in the Xiangxi River after impoundment of TGR. In July-August 2004 (rainy season) Cryptophyta bloom occurred in the downstream of the Xiangxi River and the influx region of the Xiangxi and the...