三峡水库蓄水后的浮游植物特征变化及影响因素

根据2003年10月和2004年4月的水生生物调查，对三峡库区二期蓄水后的浮游植物组成与分布变化进行研究，探讨水力学与营养盐条件变化对库区浮游植物结构与数量的影响。结果表明，库区浮游植物以硅藻类为优势种，2003年10月数量介于2.02×104~31.6×104个/L之间，与未蓄水前相比无明显变化，2004年4月浮游植物种类与数量发生较大变化，部分断面浮游植物数量显著增加，总体介于3.18×104~16 288×104个/L之间。通过对浮游植物与水力学条件、营养盐水平的关系分析，发现蓄水前后水动力学条件的变化与所形成的空间差异是造成浮游植物变化的关键因素，而偏高的营养盐水平则为浮游植物的生长创造了有利条件。为此，根据流速差异将库区水体划分为河流型水体、过渡型水体、湖泊型水体三种类型，对比分析表明过渡型水体和湖泊型水体的浮游植物数量在二期蓄水后增加较多，它们是三峡库区富营养化暴发的敏感区域。

CHARACTERISTICS OF PHYTOPLANKTON COMPOSITION WITH ANALYSIS OF ITS IMPACT FACTORS AFTER IMPOUNDING OF THE THREE GORGES RESERVOIR

According to the aquatic ecosystem investigations in October of 2003 and April of 2004, the composition and quantity of phytoplanktons after impounding of the Three Gorges Reservoir were studied. We discussed the influence of water dynamics condition, water nutrient level on the phytoplankton components and quantity. The results indicated that dominated species of phytoplankton in investigated area were diatoms, and the quantity of phytoplankton investigated on October of 2003 was not obviously different from that before impounding, and was between 2.02×104 individuals/L and 31.6×104 individuals/L. The quantity of phytoplankton increased obviously between 3.18×104 individuals/L and 16 288×104 individuals/L on April of 2004. According to the change of hydraulic condition, the reservoir is plotted to three types of waterbody; the upstream of Wushan County of Yangtze River belongs to river type, and section from Wushan County to the Three Gorges Reservior is transition type, and the estuaries and backwaters of tributary located in section from Wushan County to the dam are lake type. The phytoplankton growing in river type water region has not increased obviously after the impounding, and those in lake type and transition type water region have increased notably. Therefore, the transition type and lake type are the eutrophication sensitive regions in the Three Gorges Reservoir.