Community Structure Characteristics of Phytoplankton in Longtan Reservoir of Hongshuihe River

Species composition,density and biomass,spatial distribution and biodiversity of phytoplankton in Longtan Reservoir were investigated during the period from Jul.9thto 23th(rainy season) and Nov.11thto 25th(dry season) 2009.Based on the results,we evaluated the situation of water quality of Longtan reservoir and investigated the impacts of hydropower development on the phytoplankton.The total of 59 species belonging to 35 genera for phytoplankton was recorded in the rainy and dry seasons.Of which,28 species in Bacillariophyta,17 species in Chlorophyta,8 species in Cyanophyta,2 species respectively in Pyrrophyta,Chrysophyta and Rhodophyta.The dominant species of phytoplankton were composed of 13 species to 4 genera,such as Melosira granulata,Fragilaria capucina,Synedra amphicephal,Pediastrum biradiatum,etc.The density and biomass of phytoplankton were 33.4 × 104ind./L and 2.580 mg/L,respectively.The Shannon-Wiener indexes and Pielou indexes were 2.58 and 0.94,respectively.According to the evaluation standards of algal biology indexes,the water quality of Logntan Reservoir belongs to mesotrophic-oligotrophic type.