长江上游曲麻莱至玉树段春秋季浮游植物群落结构及多样性评价

于2012年春季（4月）和秋季（10月）对长江上游曲麻莱至玉树段的浮游植物进行初步研究。结果显示：浮游植物共3门62种（属），以硅藻门最多，42种（属），占678%，其次是绿藻门11种（属），占177%，蓝藻门9种（属），占145%。浮游植物优势种为普通等片藻（Diatoma vulgare）、长等片藻（Diatoma elongatum）、尖针杆藻（Synedra acus）、曲壳藻（Achnanthes sp）、舟形藻（Navicula sp）、桥弯藻（Cymbella sp）、脆杆藻（Fragilaria sp）、直链藻（Melosira sp）、异极藻（Gomphonem sp）、菱形藻（Hantzchia sp）、小环藻（Cyclotella sp）、小颤藻（Oscillatoria tenuis）、席藻（Phormidium sp）和小球藻（Chlorella sp）14种，其中硅藻门12种（属），占优势种类的786%。浮游植物种类组成的季节变化不明显，春季（4月）和秋季（10月）均以硅藻为优势种群。浮游植物平均数量3487×104 cells/L，平均生物量0138 8 mg/L，硅藻数量和生物量分别占8786%和9668%,为优势种群。浮游植物现存量表现为春季高于秋季，支流高于干流。Shannon Wiener指数平均值251，Pielou指数平均值070，Marggalef指数平均值089，Shannon Wiener指数、Pielou指数和Marggalef指数是秋季高于春季。结合浮游植物各项评价指标，得出长江上游曲麻莱至玉树段浮游植物群落结构比较稳定，种类分布较为均匀，水体属贫营养型，水域生态环境良好

COMMUNITY STRUCTURE AND DIVERSITY ASSESSMENT OF PHYTOPLANKTON |FROM QUMALAI TO YUSHU SECTION IN THE |UPSTREAM REACH OF THE YANGTZE RIVER IN SPRING |AND AUTUMN

The Yangtze River originates from Geladandong snow mountain located at the north of Tanggula mountains It is 1 217 km long in Qinghai province. In order to know more about community structure of phytoplankton from Qumalai to Yushu section in the upstream reach of the Yangtze River and to provide important basic data and scientific basis for water ecological environment evaluation and reasonable development and utilization of water resources from Qumalai to Yushu section in the upstream reach of the Yangtze River. The phytoplankton community from Qumalai to Yushu section in the upstream reach of the Yangtze River was investigated in spring(April) and autumn(October),2012 The community structure and environmental conditions were analyzed according to species composition,quantity,biomass and Shannon Wiener diversity and the Pielou diversity and Marggalef diversity.The results showed that most of the phytoplankton was river type It was adapt to the piateau climate and watery environment.There were 3 phyla including 62 species of phytoplankton from Qumalai to Yushu section in the upstream reach of the Yangtze River in spring and autumn.Bacillariophyta were represented by the highest number of taxa(42，678%), follwed by Chlorophyta(11，177%)，Cyanophyta(9，145%) .14 dominant species were Diatoma vulgare，Diatoma elongatum，Synedra acus，Achnanthes sp.，Navicula sp.，Cymbella sp.，Fragilaria sp.，Melosira sp.，Gomphonem sp.，Hantzchia sp.，Cyclotella sp.，Oscillatoria tenuis，Phormidium sp.and Chlorella sp.,among which 12 species were Bacillariophyta. As the seasons changed,the variation of phytoplankton was not obvious. Bacillariophyta were dominant population in spring(April) and autumn(October).The phytoplankton density from Qumalai to Yushu section in the upstream reach of the Yangtze River in spring(April) and autumn(October) ranged from 1263×104cells/L to 4541×104cells/L, with the averge of 3487×104 cells/L，and the phytoplankton biomass ranged from 0050 8 mg/L to 0298 9 mg/L, with the averge of 0138 8 mg/L.The mean density and the mean biomass of Bacillariophyta was 87.86% and 96.68%，respectively. The phytoplankton standing crops showed higher in spring (April) than in autum (October)， and higher in tributaies streams than in main streams.The mean Shannon Wiener diversity was 2.51，the mean Pielou diversity was 070，and the mean Marggalef diversity was 089. The Shannon Wiener diversity, the Pielou diversity and Marggalef diversity was higher in autumn(October) than spring(April).Compared with the research of the middle and lower reaches of the Yangtze river, proportion of Bacillariophyta from Qumalai to Yushu section in the upstream reach of the Yangtze River was higher than the middle and lower reaches of the Yangtze River At the same time,that result showed that the quality of water at Qumalai to Yushu section in the upstream reach of the Yangtze River was better than the middle and lower reaches of the Yangtze River.Combined with the indicators of phytoplankton, these structure characteristics indicated that phytoplankton from Qumalai to Yushu section in the upstream reach of the Yangtze river was more stable,species distribution was more evenly，trophic state of this river was oligotraphentic,and the aquatic environment was good