Research On Phytoplankton Variation In The Yangtze And Jialing Rivers Confluence In Chongqing

The Yangtze and Jialing Rivers confluence of Chongqing urban city is located in terminal of the Three Gorges reservoir. It receives heavy multi-source pollution of Chongqing urban city and water from uptream, serves as major water supplying source and makes great influence on water quality downstream. With up-down water level after the Three Gorges Reservoir is officially dispatched, the algae constructure and abundance will change with hydrology and climate. This article is on investgating and studying on water quality and phytoplankton growth of the two rivers confluence, analyzing algae chatracter and seasonal variation under parameters compositive effect, and making ecological evalucation of water quality. Then through experimenting on silt and velocity's influence on algae, the phytoplankton growth is analyzed and forecasted. From Aug., 2004 to Aug., 2005, The nitrogen content, phosphorus content,permanganate index and so on had been achieved eutrophication level. In general, 7 phyla, 59 genera and 120 species (including varieties) of phytoplankton community in the waters of the two rivers confluence were identified. The proportion of the community composition was: Bacillariophyta 56.7%, Chlorophyta 25.8%, Cyanophyta 6.7%, Euglenophyta 4.2%, Cryptophyta 2.5%, Chrysophyta 2.4% and Pyrrophyta 2.1%. Melosira sp., Cyclotella sp., Diatoma sp., Fragilaria sp., Synedra sp., Navicula sp., Cymbella sp. and Gomphonema sp. in the diatiom, Eudorina sp. and Scenedesmus sp. in the green-algae, Oscillatoria sp. and Phormidium sp. in blue-algae predominated. Diatom abundance propotion dominated the trend of total algae amount. In spring, phytoplankton abundance in The Jialing River achieved the peak value with Cyclotella sp. high amount, which exceeded the one in the Yangtz River of the corresponding period and all other water samples. The phytoplankton abundance of each sampling station ranged: 1.14×104~205.92×104cells/L, Chla ranged: 2.7~45.2μg/L, they both achieved maximum Mar. in Jialing River and minimum Sep. in Yangtze River. The phytoplankton amount varied consistently with time in each sampling station, maximum in spring, followed by early summer, and minimum in autumn.Effected by compositive factors,there was unconspicuous correlation between the existing algae amount with single factor of water temperature, nitrogen and phosphorus content,silt content and velocity of flow. Comparative analysis showed that the peak phytoplankton reproductions need enough nutrition(TN1.73～1.95mg/L,TP0.11～0.43...