澜沧江源区浮游植物群落特征及其对水质的指示作用

为了探究澜沧江源区水生态现状与变化趋势,在干流囊谦段布置多昌、扎曲大桥及香达3个监测点,支流选择子曲的下拉秀、尕麻和野吉尼玛3个监测点,共计6个监测点位,于2016年7月(夏季)和10月(秋季)对澜沧江源区干流及其支流浮游植物进行了调查,以期为三江源区水生态保护与管理提供科学依据。结果表明:(1)记录浮游植物7门、47种,其中硅藻(21种)和绿藻(14种)为主要成分,分别占总种类数的45%和30%;时空差异明显,夏季较秋季种类丰富,支流较干流种类丰富;优势种以硅藻为主,其中针杆藻(Synedra sp.)为两季度绝对优势种;(2)澜沧江源区浮游植物密度为5.4×10~4～230×10~4个/L,平均密度为79×10~4个/L,硅藻贡献最大;时空差异明显,秋季高于夏季,支流高于干流;(3)浮游植物Shannon-Wiener多样性指数(H)夏季为2.32,秋季为2.72,Pielou均匀度指数(J)夏季为0.73,秋季为0.70。研究显示,澜沧江源区水质介于极贫营养至中营养之间,处于轻度污染至无污染状态,水生态状况整体优良。

Phytoplankton Structure and Water Quality Assessment in the Source Region of Lancang River

In order to understand the general situation of hydroecology in the source region of the Lancang River, an investigation of phytoplankton was carried out here in July (Summer) and October (Autumn) 2016. A total of 47 species of phytoplankton were identified, belonging to7 phylum. The main taxa were Bacillariophyta (21 species) and Chlorophyta (14 species), which accounted for 45% and 30% of the total number respectively. The dominant species were mostly diatoms, and Synedra sp. aculeate was the most abundant one. Species number in Summer was higher than in Autumn, and species number in branch river was higher than in main river. Cell density of phytoplankton was 5.4×10_⁴ cells/L~2.3×10_⁶ cells/L, and the mean density was 7.9×10_⁵ cells/L. Diatom contributed the most in cell density. Cell density in Summer was lower than in Autumn, and cell density in branch river was higher than in main river. Compared with the middle and lower reaches of the Lancang River, the diversity and density of algae in the upper reaches were low. Cell density, Shannon-Wiener biodiversity index and Pielou evenness index of phytoplankton indicated that the water quality in source region of the Lancang River were good, which was in extremely poor nutrition level or the poor nutrition level.