Community structure characteristics of phytoplankton along a cascade of reservoirs in Xiangxi River Basin, Three Gorges Reservior

Abstract

于2005年10月、2006年1、4、7月对三峡水库香溪河流域3座水库(古洞口一级水库、古洞口二级水库和香溪河库湾)组成的梯级水库的浮游植物种类组成、优势种、群落结构、密度和生物多样性指数进行了周年调查研究.共鉴定出浮游植物7门58属121种(含变种),以绿藻和硅藻种类最多,绿藻有26属49种,占40.50%;硅藻14属41种,占33.88%;其次是甲藻,3属11种,占9.09%;蓝藻5属7种,占5.79%;隐藻3属7种,占5.79%;其它藻类仅占4.96%.浮游植物在古洞口一级水库共有25属31种,古洞口二级水库29属40种,香溪河库湾46属81种.优势度分析显示:古洞口一级水库藻类优势类群为硅藻门、绿藻门,古洞口二级水库为硅藻门、隐藻门和甲藻门,香溪河库湾为绿藻门、硅藻门、甲藻门和隐藻门.3座水库浮游植物年均密度分别为1.110×10⁶、4.837×10⁵和1.734×10⁶ cells/L;其中,最高密度出现在香溪河库湾(4.87×10⁶ cells/L),最低密度出现在古洞口二级水库(5.76×10⁵ cells/L).运用主成分分析对梯级水库进行水质分析,表明沿着水库的梯度水质逐渐恶化.Shannon-Wiener多样性指数和Pielou均匀度指数在3座水库间无明显差异,而香溪河库湾Margalef丰富度指数显著大于古洞口一级、二级水库.前两个指数与浮游植物优势种的评价结果显示,香溪河流域梯级水库处于中污染状态.;Xiangxi River originates from the Shennongjia Forest region and is the largest tributary in Hubei Province of Three Gorges Reservoir. Three reservoirs(Gudongkou Reservoir 1, Gudongkou Reservoir 2 and Xiangxi Bay of Three Gorges Reservoir) in Xiangxi River Basin were selected to investigate phytoplankton ecology in such a reservoir cascade system. In this study, phytoplankton composition, dominant species, community structure, abundance and biodiversity index were investigated and analyzed from October 2005 to July 2006. A total of 121 species, belonging to 58 genera in 7 phyla were identified, among which Chlorophyta(49 species of 26 genera) is the most important compontent, accounting for 40.50% of the total; followed by Bacillariophyta (41 species of 14 genera) for 33.88%, and Pyrrophyta(11 species of 3 genera) for 9.09%, Cyanophyta(7 species of 5 genera) for 5.79%, Cryptophyta(7 species of 3 genera) for 5.79% and other species for 4.96%. 31 species of 25 genera, 40 species of 29 genera and 81 species of 46 genera were found in Gudongkou Reservoir 1, 2, and Xiangxi Bay, respectively. The dominant species in Gudongkou Reservoir 1 belonged to Bacillariophyta, Chlorophyta, while Bacillariophyta, Cryptophyta and Pyrrophyta dominated in Gudongkou Reservoir 2. Chlorophyta, Bacillariophyta, Pyrrophyta, Cryptophyta also played an important role in Xiangxi Bay. The annual abundance of phytoplankton community in the three reservoirs was 1.110×10⁶, 4.837×10⁵ and 1.734×10⁶ cells/L, respectively. It had highest density in Xiangxi Bay(4.87×10⁶ cells/L) and lowest density in Gudongkou Reservoir 2(5.76×10⁵ cells/L). Principal Component Analysis was applied to analyze the water quality of the three reservoirs. The result implies that the water quality was degrading along the cascade of reservoirs. There were no significant differences in diversity index(H) and evenness(J) among the three reservoirs, while the Margalef index of Xiangxi Bay was significantly larger than that of Gudongkou Reservoir 1 and Gudongkou Reservoir 2. The valuation results by the first two indices and dominant phytoplankton species showed that the cascade reservoirs in Xiangxi River Basin were of intermediate pollution state.