沅水浮游植物群落结构特征

于2005年3、6、9、12月对沅水浮游植物群落结构进行了调查。结果表明:沅水浮游植物共计6门147种,以硅藻和绿藻为主,分别占43.53%和36.73%。浮游植物平均密度为2.21×105ind./L,蓝藻密度最大为1.33×105ind./L;浮游植物平均生物量为3.97 mg/L,蓝藻生物量最大为3.42 mg/L。浮游植物季节变化比较明显,密度秋季最大(4.64×105ind./L),夏季最小(1.6×104ind./L);生物量冬季最大(12.86 mg/L),夏季最小(0.2 mg/L)。水平分布密度和生物量均是牛鼻滩站最大,分别为6.03×105ind./L和29.6 mg/L。调查显示沅水浮游植物中巴豆叶脆杆藻、颗粒直链硅藻、钝脆杆藻、美丽星杆藻、细星杆藻、格孔单突盘星藻、泥污颤藻、铜绿微囊藻等为优势种。浮游植物Shannon-Wiener多样性指数较低,在1～2之间。指数变化由高到低分别为冬季、秋季、春季、夏季。

Community Structure of Phytoplankton in Yuanshui River

Phytoplankton community structure of Yuanshui River was investigated in March,June,September,December,2005.147 species from 6 phylum of phytoplankton were identified.The dominant algaes were Bacillariophyta and Chlorophyceae with a ratio of 43.53% and 36.73%,respectively.The average density of phytoplankton was 2.21×105 ind./L.The predominant algae was Bacillariophyta with 1.33×105 ind./L.The average biomass of algae was 3.97 mg/L,Chlorophyta was the largest with the biomass of 3.42 mg/L.There were significant differences of phytoplankton density and biomass in four different seasons.The maximum 4.64×105 ind./L was in autumn and the minimum 1.6×104 ind./L was in summer.About biomass,the maximum 12.86 mg/L was in winter and the minimum 0.2 mg/L was in summer.The density and biomass of phytoplankton in the station of Niubitan were both the largest in all nine stations,with 6.03×105 ind./L and 29.6 mg/L.It showed that Fragilaria crotonensis,Melosira granulata,Fragilaria capucina,Asteronella formosa,Asteronella gracillima,Pediastrum simplex var.clathratum、Oscillatoria limosa、Microcystis aeruginosa were dominant species.Shannon-Wiener diversity index of phytoplankton was low,between 1 and 2.In four seasons,the index in winter was the largest of all,second in autumn,third in spring and the least in summer.