长江源区浮游植物群落结构及分布特征

地处青藏高原腹地的长江源区是长江流域的水源涵养地和生态系统的天然屏障,同时也是自然生态系统最敏感、生态环境十分脆弱的地区,浮游植物作为水体生态系统中的初级生产者,其群落结构对反映水体质量具有重要的指示作用。为探究长江源区水环境特性和浮游植物群落特征,于2018年3月份与10月份对长江源区10个典型河段的水环境因子与浮游植物群落组成进行了系统调查。结果显示:10月份各调查河段流速、浊度、水温及电导率等水环境参数均比3月份高;同一月份中,楚玛尔河的浊度、盐度、电导率等水环境参数均显著高于其余河段;两个月份各调查河段的pH、溶解氧以及亚硝酸盐氮等指标差异不显著。采样调查共鉴定出浮游植物4门28属58种,其中以硅藻、绿藻和蓝藻物种数占优,分别占总数的79.3%、10.4%和8.6%。调查期间,长江源区浮游植物密度在6.06×10~4～39.90×10~4 cells·L~(-1)之间,平均生物量为0.59 mg·L~(-1)。浮游植物优势种有美丽颤藻(Oscillatoria formosa)、普通等片藻(Diatoma vulgare)、脆杆藻(Fragilaria sp.)、针杆藻(Synedra sp.)、舟形藻(Navicula sp.)、桥弯藻(Cymbella sp.)、小球藻(Chlorella sp.)等。两个月份Shannon-Wiener多样性指数(H’)均值分别为3.06和3.12,Margalef丰富度指数(D)均值为1.17和1.52,Pielou均匀度指数(J)均值为0.90和0.82。结合水体营养盐指标、浮游植物密度及多样性指数等指标对水质评价,长江源区水质总体呈无污染或轻度污染状态。

Phytoplankton Community Structure and Distribution Characteristics in the Source Region of the Yangtze River

The source region of the Yangtze River, located in the central Qinghai-Tibetan Plateau, has water conservation function, and is also a natural barrier of ecosystem for the Yangtze River Basin. Meanwhile, natural ecosystem is the most sensitive, and eco-environment is very fragile in this region. As a primary producer in the aquatic ecosystem, phytoplankton plays an important role in reflecting water environment quality. To explore water environment properties and phytoplankton community characteristics in the source region of the Yangtze River, systematic surveys of water environments and phytoplankton in 10 typical sections were carried out in March 2018 and October 2018. In October, water environmental parameters such as flow velocity, turbidity, water temperature, and conductivity of the sections were all higher than those in March. These water environmental parameters such as turbidity, salinity, conductivity of the Chumaer River were significantly higher than other river segments in the same month. There was no significant difference in pH, dissolved oxygen and nitrite nitrogen among the river segments in the two months. A total of 58 phytoplankton species belonging to 4 phyla and 28 genus were identified, among which Bacillariophyta (79.3% of the total species number), Chlorophyta (10.4%), Cyanophyta (8.6%) were dominant. The variations of phytoplankton density were 6.06×104-39.90×104 cells·L-1, the average of phytoplankton biomass was 0.59 mg·L-1 during the investigation. The dominant species were Oscillatoria formosa,Diatoma vulgare,Fragilaria sp., Synedra sp., Navicula sp., Cymbella sp., and Chlorella sp.. In March 2018 and October 2018, the Shannon-Wiener diversity means were 3.06 and 3.12, the Margalef diversity means were 1.17 and 1.52, and the Pielou diversity means were 0.90 and 0.82, respectively. Combined with nutrient indexes, phytoplankton density and diversity indexes, water quality in the source region of the Yangtze River was generally non-polluted or slightly polluted.