三峡水库汛期运行对长江干支流浮游植物的影响

Impact of the Operation of Three Gorges Reservoir During Wet Season on Phytoplankton in Main Stem of Yangtze River and Its Tributaries

为了探究三峡水库175m蓄水后工程运行对库区浮游植物影响,于汛期对长江干流及其25条支流浮游植物进行了调查,长江干流上游至下游共设朱沱、丰收坝、寸滩等13个采样点,綦江、嘉陵江、五布河等25条长江支流共设94个采样点。结果表明：（1）干流145m淹没河段,硅藻种类比例明显降低,蓝藻、绿藻、甲藻、隐藻种类比例明显升高,但主要种类组成仍为硅藻-绿藻-蓝藻型;现存量升高不明显,硅藻比例明显降低、蓝藻比例明显升高;出现蓝藻优势种类且占比最高,硅藻优势种类占比下降,但仍为最高优势度种类,且最高其优势度基本不变;浮游植物Shannon-Wiener多样性指数（H′）、Pielou均匀性指数（J）下降不明显;（2）145m未淹没支流,175m淹没河段重新恢复为自然河流状态,其浮游植物群落也恢复到自然河流状态;（3）145m淹没支流河口,浮游植物种类组成特点明显改变;现存量明显升高,其组成发生较大变化;硅藻优势种类占比、最高优势度明显下降,绿藻、蓝藻、隐藻、甲藻等优势种类相应升高;H′和J明显降低;（4）从上游至下游,干流和25条支流河口硅藻种类比例由最高到最低变化,蓝藻、绿藻种类比例由较低到最高变化。

In order to study the influence of 175 mimpoundment project operation on phytoplankton,the phytoplankton was investigated during wet season in main stem of Yangtze River and its 25 tributaries in the Three Gorges Reservoir.In this research,thirteen sampling sites was set in the main stem of Yangtze river and ninety-four in the tributaries.Both qualitative and quantitative samples of phytoplankton were collected and the work of species identification was done with microscope,and Shannon-Wiener diversity indices,Pielou evenness indices and the species dominance were calculated.Results show that：（1）Compared to the unsubmerged reaches when the water level was 145 m,in backwater area（145 m）of Yangtze River,bacillariophyta species proportion obviously decreased,and cyanophyta,chlorophyta,pyrrophyta and cryptophyta species proportion obviously increased,but species composition dominated by bacillariophya,chlorophyta and cyanophyta was not changed.And standingcrop increased not obviously.However,bacillariophyta species proportion obviously decreased and cyanophyta species proportion obviously increased.In dominant species,the proportion of cyanophyta was the highest,bacillariophyta proportion declined,and the dominance of bacillariophyta remained the same as the inflooded reaches.The H′（Shannon-Wiener diversity index）and Jof（Pielou evenness index）of phytoplankton declined not obviously.（2）The flooded reaches when the water level of the Three George Reservoir was 175 m and unsubmerged（145 m）tributaries were restored to natural river state again,and correspondingly phytoplankton community were restored to natural river state.（3）Phytoplankton species composition changed obviously in the estuary of flooded（145 m）tributaries.Compared to the unsubmerged reaches when the water level was175 m,the standingcrop increased obviously and composition was changed greatly.In dominant species,bacillariophyta proportion and the highest dominance declined obviously,chlorophyta,cyanophyta,pyrrophyta and cryptophyta proportions increased correspondingly.The H′and Jof phytoplankton declined obviously.（4）From upstream to downstream,in main stem of Yangtze River and estuary of 25 tributaries,bacillariophyta species proportion were changing from the highest to lowest,and cyanophyta and chlorophyta species proportion were changing from the lower to the highest.