三峡水库长江干流及其支流枯水期浮游植物多样性与水质

Phytoplankton diversity and water quality in the main stream and tributaries of Three Gorges Reservoir region of Yangtze River during dry season

2010年4月对长江干流和26条支流未淹没区与回水区的浮游植物进行调查.结果表明,硅藻、绿藻和蓝藻共占浮游植物种类的93.33%～93.88%.干流优势种类有1门1种、未淹没区有3门6种、回水区有5门6种,出现率分别为15.38%、9.23%和25.00%.回水区现存量平均值最高、未淹没区其次、干流最低.现存量组成在干流、未淹没区和回水区之间有差异,绿藻所占比例干流最高,硅藻所占比例未淹没区最高,隐藻、蓝藻和甲藻所占比例均在回水区最高.Shannon-Wiener多样性指数(H')和Pielou均匀性指数(J),未淹没区最高、干流次之、回水区最低.17条支流回水区H'和8条支流回水区J均低于未淹没区.水质评价显示,轻或无污染断面(采样点)的比例,干流为76.92%,未淹没区为84.62%,回水区为47.06%.19条(73.08%)支流回水区出现中污染或重污染,7条(26.92%)支流未淹没区出现中污染或重污染.三峡工程蓄水对回水区浮游植物与水质影响比长江干流更大.

A survey on phytoplankton was carried out along the main stream of the Yangtze River and inundated and backwater are- as of 26 tributaries in April, 2010. Species of diatoms, green algae and cyanobacteria accounted for 93.33% -93.88% of the total phytoplankton. Dominant species in the main stream, inundated area, and backwater area were I species in 1 phylum, six species in 3 phyla and 6 species in 5 phyla, respectively. The occurrence rates of dominant species in the main stream, inundated area, and backwater area were 15.38% , 9.23% and 25.00% , respectively. The average value of phytoplankton standing stock was the highest in backwater area, followed by inundated area and the lowest in the main stream. Compositions of phytoplankton standing stock were different among the main stream, inundated area and backwater area. The proportions of green algae and diatom were the highest in the main stream and inundated area, while the proportions of cryptophyta, cyanophyta and pyrrophyta were all the highest in backwater area. Shannon-Wiener diversity indexes and Pielou evenness indexes were the highest in inundated area, fol- lowed by the main stream, and the lowest in backwater area. Shannon-Wiener diversity indexes of backwater area of 17 tributaries and Pielou evenness of backwater area of 8 tributaries were both lower than those inundated area. Water quality assessment indicated that the proportions of slightly polluted or not polluted monitoring sections in the main stream, inundated area and backwater area were 76.92% , 84.62% and 47.06% , respectively. Moderate polluted or seriously polluted were found in backwater area of 19 tributaries （73.08%） and inundated area of 7 tributaries （26.92%）. The influence of the Three Gorges Dam Project on pbytoplankton and water quality in backwater area is greater than that in the main stream of Yangtze River.