Phytoplankton Composition And Variation In The Exit Section Of Jialing River

The exit section of Jialing River flews through Chongqing City, it receives heavy multi-source pollution of Chongqing urban city and water from upriver stream, serves as water supplying source and makes great influence on water quality downstream. This article is on investigating and studying on phytoplankton growth and dominant species of alga in the exit section of Jialing River; analyzing the factors that effects the composing, distributing and quantity of phytoplankton in this water area; and finding out alga character and seasonal variation under parameters effect, and making ecological evaluation of water quality.7 phyla, 60 genera and 120 species of phytoplankton community were identified in the exit section of Jialing River from Feb, 2005 to July, 2006. The proportion of the community composition was: Bacillariophyta 49.5%, Chlorophyta 29.0%, Cyanophyta 11.2%, Euglenophyta 3.7%, Cryptophyta 2.8%, Pyrrophyta and Chrysophyta 2.1% each. Melosira sp., Cyclotella sp., Diatoma sp., Fragilaria sp., Navicula sp., Cymbella sp. and Gomphonema sp. in the diatiom, Chloralla sp. and Scenedesmus sp. in the green-algae, Nostol sp. and Phormidium sp. in blue-algae predominated. Diatom abundance proportion dominated the trend of total algae amount. In spring, phytoplankton abundance in dock four section achieved the peak value with Cyclotella sp. high amount, which exceeded the other ones in the Jialing 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. The phytoplankton amount varied consistently with time in each sampling station, maximum in spring, followed by early summer, and minimum in autumn and winter.The abundant nitrogen and phosphorus content in exit section of Jialing River provided essential physical condition for phytoplankton growth. After analyzing relation between phytoplankton and main factors of eutrophication we concluded: alga amount had no remarkable relation with phosphorus content, but it had relation with water temperature, nitrogen content and velocity in most period of a year. For the phytoplankton growth was effected by compositive factors, no single factor could reflect the especial growth of Cyclotella sp. Phytoplankton in different waters of velocity: in slower water, nitrogen and phosphorus content were higher, alga amount was larger than that in faster water; and because relatively fast velocity in the river, Diatom predominated in all waters, other kinds of alga were fewer; Diatom proportion was greater in faster water, green-algae and blue-algae reversed.Overall evaluation of the phytoplankton showed that, the exit section of Jialing River water body has been in the rich nutritional level. Due to influence of hydrology and climate, the existing algae amount didn't correspondingly make obvious response, and it's in relative lower level except for Spring. Nutrition degree in Spring is highest, followed by Summer, and other periods is lower. Nutrition degree of dock four is higher than the other waters.Study on influence of phytoplankton and silt as well as velocity was not enough in this research, and those works could be developed in the future. And it's recommended to search out the reference species that occurring frequently and have remarkable correlation with total alga amount, and we can attempt to construct algae-amount dynamic model by reference species in order to forecast nutrition state of the exit section of Jialing River and the Threegorge reservoir.