三峡库区藻类种群结构与密度变化及其与氮磷浓度的相关性分析

2003年1月~2004年12月对三峡湖北库区江段5个采样点及其一级支流——香溪河流域6个采样点的浮游藻类进行了为期2周年的调查，共采集和鉴定浮游藻类定性和定量水样1 000余个，获得有效数据2 000多个。数据显示，蓄水前（2003年1月~2003年6月）、蓄水1周年（2003年6月~2004年5月）和蓄水1.5年（2004年6月~2004年12月）3个时间段之间，被调查水域的浮游藻类群落结构、细胞密度和水质状况均存在一定的差异。总体而言，藻类的群落结构干流江段以硅藻为主，绿藻次之；支流水域以绿藻占据首位，硅藻次之。被调查水域藻类的细胞密度随蓄水时间的延长呈增长趋势，并显示一定的季节性差异；藻类细胞密度与TP的相关性比与TN的相关性更为密切。目前干流江段和支流水域的水质状况分别为中营养型和中－富营养型，较建坝蓄水前的水质有所下降。在分析导致藻类种群结构和细胞密度变化原因的基础上，建议加强对库区水质的检测和保护，以杜绝和防止库区的水域环境进一步恶化。

CHANGES IN ALGAL COMMUNITY STRUCTURE AND ALGAL DENSITY IN RELATION TO TN AND TP IN THE THREE GORGES RESERVOIR

Algal community structure and algal density in the Three Gorges Reservoir were investigated from January 2003 to December 2004.Eleven sampling sites were selected,five of which were in the mainstream and six in the anabranch.Samples were taken once a month.More than 1 000 samples of algae were identified.The results were discussed in three periods,i.e.before water storage(2003.01-06),one year duration after water storage(2003.06-2004.05),and one and a half year duration after water storage(2004.06-12).It was shown that the algal species composition and cell densities in the reservoir varied markedly among the three periods.At present,the algal community in mainstream was dominated by Bacillariophyta,and then Chlorophyceae.In the tributary,species of Chlorophyta were most frequently observed,and then species of Bacillariophyta.The mainstream and the tributary after water storage could be referred to the mesotrophic and to meso-and eutro-phic types,with water quality deteriorating than before water storage.The cell densities of algae in the three periods showed an increasing trend especially in the tributary.It proved that the water quality of the reservoir has been caused by the significant reduction in current speed and the increase of nutrients concentration.In order to protect the water quality of the Three Gorges Reservoir,it is important to prohibit the discharge of wastewater with high phosphorus and nitrogen concentration.