通过2003年3月至2005年8月对南水北调中线水源区水体浮游植物的调查,结果表明:该水域共有浮游植物8门63属96种及变种,其中以硅藻的种类最多,其次是绿藻和蓝藻。藻类的细胞密度表现出明显的季节变化,夏季最高冬季最低。从近3年的浮游生物检测结果可知,整个水源区年平均藻类细胞密度为109.33×10⁴ cells·L^-1,处于较低的水平,而且未检出水体重污染指示种,充分说明南水北调中线水源区富营养化程度较低。运用Margalef和Menkinick多样性指数对该水域的水质进行评价,数据显示2003~2005年该水源区的d值和α值,各采样点之间的差异并不显著,说明各采样点的水质营养状况虽有差异,但总体水平基本相当。水质评价结果:水体为寡污型,基本处于中营养状态。通过水生生物资源的调查,做好水源区的长期生态监测,可为建立中线水源区长期生态研究数据信息库及库区生态环境保护政策制定提供理论依据,对保证中线水质质量十分重要。

Background and Aims The water source area of the middle line project for transferring water from south to north is in the interface of Henan, Hubei and Shaanxi Provinces, the largest source of freshwater in Asia. Economic development of the area surrounding the Danjiangkou Reservoir will affect water quality. The objective of this study is to develop methods for monitoring biological resources, including annual changes of plankton in the reservoir, in order to provide a scientific base for sustainable exploitation, protection of biological resources, regulations for water resource protection, and establishment of a database for long-term ecological research on the middle line project.
Methods Water samples were collected using standard methods at three points of Qushou, Kuxin and Dashiqiao from March 2003 to August 2005, for biological, physical, and chemical analyses. Qualitative samples were collected using 25 phytoplankton networks, and taxa were identified by ordinary microscopes. Quantitative samples were collected using bottles and were fixed in Lugol's medium. Samples were condensed and counted in the laboratory under light microscopy with a phytoplankton counter frame. Algal diversity was calculated using Margalef and Menkinick diversity indices.
Key Results Samples contained 96 species and varieties, 63 genera, and 8 divisions of phytoplankton; diatoms were the most important component, followed by green algae and blue green algae (cyanobacteria). Cell densities exhibited seasonal changes, with maximum values in summer and minimum values in winter. Investigation of phytoplankton from three recent years showed an average annual density of algae of 109.33×10⁴ cells·L^-1 at low water level, and no pollution of indicator species was detected in the water sources. Application of diversity indices to assessment of water quality showed the d, α value, and differences among the different sample sites were small. There were only small differences in water quality nutrition status.
Conclusions Water quality indicated mesotrophy and middle nutrition status. This study provides a scientific base for long-term ecological research on biological resources and for policy development for ecological environmental protection. It will have an important effect on the water quality on the middle line project.