Abstract:

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.

Key words: Water source area of the middle line project of transferring water from south to north, Phytoplankton, Biological monitoring, Species community, Water quality assessment