Eutophication of large freshwater Ecosystems in Korea

다국어 초록 (Multilingual Abstract)

Freshwater ecosystems in Borea consists mostly of reservoirs and regulated rivers. About 18,000 reservoirs have been constructed and they contribute to the most of water supply. The number of natural lakes is less than several hundreds and they are small. Reservoirs in the mountainous district are usually mesotrophic, whereas downstream reservoirs are eutrophic, and estuarine reservoirs are hypertrophic. Eutrophication is also troublesome in streams and rivers in Korea. Downstream regions of slow- flowing rivers show high density of phytoplankton. Phosphorus is thought to be the limiting factor of algal growth in deep montane reservoirs, while hydraulic residence time and light penetration are thought to be limiting factors in eutrophic downstream reservoirs because nutrients concentration are so high in the downstream region. According to the national budget of phosphorus, fertilizer and livestock manure are m꼰or sources of phosphorus, contributing 133,400 tonP/yr and73,700 tonP/yr, respectively, while human excretion discharges 30,000 tonp/yr.