Ecological monitoring and investigation of Peridiniopsis sp. of the main tributaries in the Three Gorges Reservoir
三峡水库支流拟多甲藻（Peridiniopsis sp.）

A consecutive investigation on the physicochemical property and phytoplankton was conducted in the main channel of the Yangtze River and Tong Zhuang River branch waterback area from 2009 to 2010. The monitoring results showed that the nitrogen and phosphorus contents in both the Yangtze River and Tong Zhuang River were higher in 2010 than in 2009,but no significant differences between the two rivers in the same year. The cell density of Peridiniopsis sp. in the waterback area of the Tong Zhuang River increased rapidly, respectively from the 13thand ninth up to the first in 2009 and 2010, and the algal water bloom occurred in February and March in 2010.The algal water bloom firstly occurred in the tail end of the waterback area, and gradually developed toward the middle and lower reaches and finally formed into a large-scale bloom, and withdrew after a period of time. The algal density was higher in the upper reach of the Tong Zhuang River with decreasing trend from the upper to lower reaches.In the same period, the occurrence frequency of the algal was less and the algal density was low in the mainstream of the Yangtze River, with the cell density in the branch waterback area lower than 30.91%. Our results indicated that the conditions in the branch waterback area are more suitable for the algal growth. Yet whether the algae water bloom occurs or not is up to hydrological factors.