Preliminary research on the algal bloom of Peridiniopsis sp in Gaolan River of the Three Gorges Researvoir

The environmental problems caused by the Three Gorges Dam extremely is worth paying attention. A part of Gaolan River became reservoir area after storing water. On 22 February 2005, a distinctive "algal bloom" was observed in Gaolan River and continued to March. The specie of Forming-algal bloom" was a soil of Peridiniopsis sp. The density of Peridiniopsis sp and chl. a concentration reached 2.4 x 10(7) cells/L and 330.73 mg/m(3) respectively during blooming. The algal bloom lasted about one month. In this paper the processes of the algal bloom and the basic phytoplankton composition were studied, and the functions of the environmental factors in the processes of the algal bloom in area scale were analysed. The environmental factors included water temperature, ammonium (NH4) nitrate (NO3) total nitrogen (TNT) total phosphorus (TP), phosphate (PO4) dissolved oxygen (DO), CODnm, silicate (SiO2) and chlorophylla (chl. a) The studies revealed:High concentration of TN and TP ect in the surface layer were likely to be one of the factors supporting the "algal bloom" in Gaolan Rive and suitable natural conditions also contributed to tile process. When the nutritions in the upper layer were consumed away gradually by Peridiniopsis sp and finally were exhausted for the development of bloom, a port of Peridiniopsis sp Sank into the bottom layer