香溪河库湾浮游藻类种类演替及水华发生趋势分析

STUDY ON THE SUCCESSION OF ALGAE AND THE TREND OF WATER-BLOOMS OCCURRED IN XIANGXI BAY

三峡水库一期工程蓄水前半年(2003年1月—2003年6月)和蓄水后(2003年7月—2004年12月)期间,香溪河库湾浮游藻类的种类演替和数量变化的调查结果。与蓄水前的数据相比,蓄水仅半年绿藻的种类数就明显增加,约相当于蓄水前的3倍;硅藻的种类数略有减少;其余各门藻类的种类数亦有轻度变化。整个调查期间,藻类细胞密度和生物量的最高峰值均出现在S6采样点,细胞密度达6.93×107cells/L(2004年6月),生物量达87.24mg/L(2004年3月),其余采样点基本显示由北向南依次递减的趋势。本文参考早期资料并比较不同类型水域中藻类的种类演替和垂直分布情况,对三峡湖北库区水域水华的发生趋势进行了分析,初步认为三峡干流江段形成藻类水华的几率较小;流动的支流水域,在阳光充足、水温逐渐升高的春季容易发生藻类水华;在较封闭的静水区则随时都有发生藻类水华的可能性。

This paper represents the results of an investigation on algal succession and the occurring trend of water-blooms in Xiangxi Bay from January 2003 to December 2004. The results were discussed in four periods. The first period was from January 2003 to June 2003, the second was from July 2003 to December 2003, the third was from January 2004 to June 2004, and the fourth was from July 2004 to December 2004, each period was 6 months. A total of 115 species of algae belonging to 7 phyla and 85 genera was observed when the Three Gorges Reservoir had been sluiced for half a year. The species number of each phylum were as follows ： Bacillariophyta 22, Chlorophyta 67, Cyanophyta 12, Pyrrophyta 4, Euglenophyta 5, Cryptophyta 2, Xanthophyta 3. The results showed that the species richness of green algae increased notably in the second period. It was almost 3 times of that before sluice, and then went down slowly in the third and the fourth period. The species richness of diatoms represented a trend of decrease. Other phyla varied slightly. The peak value of cell density and biomass of algae were both noted at the S6 station with the highest cell numbers of 6.93 × 10^7cells/L （June）and the most biomass of 87.24mg/L （March）. The minimal values were almost noted at the S1 station except in March. According to the investigated results, the authors give a forecast analysis on the trend of water-blooms occurring in the Xiangxi Bay. We predict that the occurring odds of water-blooms is small in the main channel, and the water-blooms are easy to occur in distributaries and some lentic areas, especially in spring when the water temperature rises gradually and sunlight becomes abundant.