Study on Community Structure of Phytoplankton in Nangqian of Lantsang River in Summer and Autumn
澜沧江囊谦段夏秋季浮游植物群落结构初步研究

Phytoplankton community in Nangqian of Lantsang River was investigated in summer(June) and autumn(September) of 2011.Results showed that there 4 phyla including 57 species of phytoplankton in Nangqian of the Lantsang River in summer and autumn.Bacillariophyta were represented by the highest number of taxa(33),follwed by Chlorophyta(13),Cyanophyta(10) and Pyrrophyta(1).The kind of diatoms which like the low temperature predominated in Nangqian in Lantsang River during summer and autumn.The species number of chlorophyta and cyanophyta were higher in autumn than that in summer,while pyrrophyta was only appeared in summer.Bacillariophyta(75.0%) was dominated in phytoplankton,including Synedra acus,Diatoma vulgare,Navicula sp.,Cymbella sp.,Achnanthes sp.,Gomphonem sp.,Oscillatoria sp.and Phormidium sp..The abundance of phytoplankton ranged from 13.26 × 104 to 375.59 × 104 cells /L with the average of 99.36 × 104 cells /L,and the biomass of phytoplankton ranged from 0.0445 ～ 1.9972 mg /L with the average of 0.4915 mg /L.The abundance and biomass of diatoms were the highest in all species,occupying 61.2% and 71.3%.Shannon-Wiener index of diversity and the Pielou index of phytoplankton were much high,with the mean values of 2.24 and 0.48,respectively.These structure characteristics indicated that phytoplankton in this river was very stable and species were distributed evenly,which suggest that this river was in oligotrophic state and the aquatic environment was good.