沱江浮游植物群落特征及水质评价

PHYTOPLANKTON COMMUNITY STRUCTURE AND WATER QUALITY ASSESSMENT IN TUOJIANG RIVER

为合理评价沱江水质现状,于2013年丰水期(8月)和枯水期(11月)对沱江浮游植物及主要水质指标进行采样调查。结果显示:(1)丰水期综合营养状态指数TLI(∑)较高,尤其是上游江段,变化范围为47.4—64.6,平均56.3;枯水期TLI(∑)变化范围为43.4—48.1,平均44.6。(2)检出浮游植物88种(属),主要为绿藻、硅藻和蓝藻。丰、枯水期浮游植物群落主要组分分别为绿藻+硅藻+蓝藻和硅藻+绿藻+隐藻。优势度分析显示,丰水期优势种主要为梅尼小环藻(Cyclotella meneghiniana)、微小平裂藻(Merismopedia tenuissima)、拉氏拟柱孢藻(Cylindrospermopsis raciborskii)等,枯水期主要为脆杆藻(Fragilaria sp.)、尖尾蓝隐藻(Chroomonas acuta)、线形舟形藻(Navicula graciloides)等。(3)丰水期浮游植物的多样性指数H?、丰富度指数d、均匀度指数J均值分别为3.66、6.21和0.69,枯水期分别为3.67、4.12和0.88。(4)聚类分析与单因素方差分析结果表明沿江水坝建设与空间分布格局对NH4+与浮游植物群落结构已有影响,表现出水坝上游湖泊型藻类数量增加、上游江段浮游植物密度高于下游江段的趋势。(5)分类回归树模型显示,营养水平与物种丰富度较高但均匀度偏低的水体中,浮游植物密度易出现高值。综合以上情况,沱江水质已处于中到富营养状态,尤其是丰水期与较上游的江段,富营养化程度更高。为预防水华的发生,出现丰富浮游植物种类的地段更应加强监控,尤其是丰水期上游的大坝坝上江段。

To assess water quality and phytoplankton biodiversity in the Tuojiang River, an upper-middle–stream river of Changjiang（Yangtze） River, Sichuan, we surveyed the phytoplankton community structure and water quality in August（wet season） and November（dry season） in 2013. Water and phytoplankton samples were collected at water surface with Schindler-Patalas trap and processed in traditional methods. Results show that, the trophic level index TLI（Σ） was higher in wet season（47.4—64.6 in average of 56.3） than in dry season（43.4—48.1, 44.6 in average）. Eighty-eight species of phytoplankton were recognized, including mainly green algae, diatoms, and cyanobacteria. Major members were green algae ＋ diatoms ＋ cyanobacteria in wet season and diatoms ＋ green algae ＋ cryptophyta in dry season. Dominant species in wet season included Cyclotella meneghiniana, Merismopedia tenuissima, and Cylindrospermopsis raciborskii, while those in dry season included Fragilaria sp., Chroomonas acuta, and Navicula graciloides. The mean values of the Shannon-Wiener diversity index H＇, Margalef abundance index d, and Pielou evenness index J on phytoplankton in wet period were 3.66, 6.21 and 0.69; and 3.67, 4.12 and 0.88 in the dry season, respectively. Cluster analysis and analysis of variance（ANOVA） show that, along-river dam construction and sampling location affected the results of NH4^＋concentration and phytoplankton community structure, showing more lake-type cyanobacteria and green algae in the upstream of dams and higher phytoplankton density in the upperstream than in the other parts. Classification and regression tree modeling showed that, phytoplankton density and richness was often high in the water where nutrition level was high but evenness was low. Therefore, the water quality in Tuojiang River was in the state of between mesotrophication and eutrophication, in particular the upper stream section in wet season. To prevent possible bloom outbreak, close watch shall be made on the sections with abundant phytoplankton species, especially the upstream of dams in upper Tuojiang River in wet season.