Eutrophication in the great lakes of the Chinese pacific drainage basin: Changes, trends, and management

Abstract

China has 25 of the world’s great lakes (>500 km2). This number of great lakes is exceeded only by Canada and Russia. Tectonic uplift and fluvial actions are the primary mechanisms resulting in the formation of these lakes. Long-term climate changes have significant impacts on these lakes, especially in terms of: (1) lake size and depth and (2) chemical characteristics. In recent years, the increased temperature has also led to the onset of the blue-green alga Microsysti in the Pacific Drainage Basin (PDB). Over the most recent 40 years, human activities have had a visible effect on the large lakes situated in the humandominated PDB. Large lakes in this basin have become depositories of agricultural, industrial, and household wastes and have shown an increased level of eutrophication and toxic chemical accumulation. These great lakes have changed from oligotrophic in the 1960s, to eutrophic in the 1980s, and to hypereutrophic in the 1990s, with increased occurrence of blue-green Microsysti blooms. These blooms have become serious concerns for water supplies and the health of people and aquatic ecosystems. Continuing disposal of untreated domestic and industrial wastes has contributed to this change. Lake management practices, such as dams and weirs for flood control and extensive use of littoral area and wetland for farming, aquaculture, and home construction, have also contributed to the acceleration of this process. With its enormous population and increasing use of large lakes, China needs to integrate its lake management programs and to plan for sustainable use of its aquatic resources. The management plan should take into consideration the environmental costs of development and the ecological service that the lakes provide. The reduction or recycling of wastes by industries needs to be closely controlled. The involvement of average citizens in decisions in environmental planning and lake management is another key to the success of managing these important water bodies.