As the last undammed tributary of the upper Yangtze River, Chishui River is an important protected aquatic habitat. There is a very close relationship between phytoplankton and the aquatic environment. Changes in phytoplank-ton composition and distribution are regularly used as indicators in environmental monitoring. Furthermore, phyto-plankton community structure can be affected by changes in the environment. In this paper, the relationship between the phytoplankton community structure and aquatic environmental factors in the Chishui River was analyzed. Phytoplank-ton data and aquatic environmental factors were obtained from research investigations in the Chishui River National Nature Reserve for Rare and Endemic Fishes in the Upper Reaches of the Yangtze River during 2007 to 2010. The in-vestigations were usually carried out each year in June, September and December. The investigations recorded 517 phytoplankton species belonging to eight phyla. Species of Bacillariophyta were the most prevalent, accounting for 67.97%, Chlorophyta and Cyanophyta species accounted for 17.83%and 10.61%, respectively, while Euglenophyta and Xanthophyta species totaled 1.98% and 1.34%, respectively. Phytoplankton species of Chrysophyta, Pyrrophyta and Cryptophyta accounted for 0.70%, 0.93% and 0.50%, respectively. Regarding phytoplankton density and biomass, average values for phytoplankton density and biomass ranged from 11.95×104 to 28.31×104 cell·L-1 and 0.36 to 0.94 mg·L-1, respectively, at the fish breeding stage. At the fish fattening stage, average value for density and biomass ranged from 10.32×104 to 33.73×104 cell·L-1 and 0.25 to 0.60 mg·L-1, respectively, while at the wintering stage the average values ranged from 11.53×104 to 26.38×104 cell·L-1 and 0.39 to 0.76 mg·L-1, respectively. For phytoplankton commu-nity biodiversity, the average Shannon-Wiener’s diversity index (H'), Margalef’s richness (d) and Pielou’s species evenness (J) were 4.42, 6.93 and 0.84, respectively. The community biodiversity results indicate that most sampling sites in the Chishui River were unpolluted, except for the Tucheng sampling site. The relationship between phytoplank-ton community structure and aquatic environmental factors was analyzed by canonical correlation analysis (CCA). The result of CCA indicated differences in the phytoplankton community structure at the three sampling stages. The aquatic environmental factors, including nitrate-nitrogen ( 3NO--N), nitrite-nitrogen ( 2NO--N) and total nitrogen (TN), had a major influence on the phytoplankton community structure at the fish breeding stage, magnesium ion (Mg2+) was the main influencing factor at the fish fattening stage, while pH, dissolved oxygen (DO), calcium ion (Ca2+) and water temperature (WT) were significant factors at the fish wintering stage.%于2007-2010年在长江上游珍稀、特有鱼类国家级自然保护区赤水河段进行浮游植物和水质监测调查研究,浮游植物调查结果显示,共鉴定出浮游植物8门517种(属),贡献率最大为硅藻门(Bacillariophyta),占藻类总数比例平均为67.97%。繁殖期浮游植物密度和生物量平均值范围分别为11.95×104~28.31×104 cell·L-1和0.36~0.94 mg·L-1；育肥期密度和生物量平均值范围分别为10.32×104~33.73×104 cell·L-1和0.25~0.60 mg·L-1；越冬期密度和生物量平均值范围分别为11.53×104~26.38×104 cell·L-1和0.39~0.76 mg·L-1。群落Shannon-Wiener多样性指数(H')、Margalef丰富度指数(d)、Pielou均匀度指数(J)平均值分别为4.42、6.93、0.84,土城采样断面水体为轻度污染,其他采样断面水体均无污染。物种-环境典型对应分析(CCA)分析显示,繁殖期群落结构主要影响因子为硝酸盐氮( NO3--N)、亚硝酸盐氮( NO2--N)、总氮(TN)等含氮营养盐类,育肥期为镁离子(Mg2+),越冬期为水温(WT)、pH、溶氧(DO)、钙离子(Ca2+)。本研究通过分析这一国家级自然保护区赤水河段的浮游植物群落结构特征,并探讨赤水河段浮游植物群落结构及其环境因子的关系,旨在为保护区赤水河段的水生态环境管理与水生生物资源保护措施的制定提供基础参考依据。
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