Rapid Recovery of Macrobenthic Communities Following Operation of Tidal Power Plant in the Lake Sihwa, Korea

초록

Lake Sihwa tidal power plant has a long history. Lake Sihwa was created on the western coast of Korea in 1994 by construction of an embankment to secure agricultural and irrigation water for the region and develop industrial/agricultural lands near the metropolitan area. Along with the new 56.5km2 freshwater lake, which is now one of the largest tidal lakes in Korea, a total of 173km2 of reclaimed land was also created. However, dike construction led to immediate desalination, eutrophication and seasonal development of bottom water hypoxia and anoxia inside the lake due to stoppage of the tidal current, various pollutants from the adjacent industrial complexes, and freshwater discharge from nearby tributary streams. Therefore, Lake Sihwa has been the subject of repeated discussions to solve this problem and was managed by regular or irregular flushing of the lake with seawater by means of sluice control from 1997 to 2011. In December of 2002, the Korean government made the decision to construct a tidal power plant (TPP) to improve water quality and generate the electricity. After seven years of construction, the tidal power plant was completed in July 2011, tested in August 2011, and has been in full operation since January 2012. The Sihwa TPP was designed for single effect flood generation that can be operated in one direction, from the sea to the lake, allowing up to 60 billion tons of seawater to be circulated annually. There was a 12-fold increase in water exchange in response to TPP operation. Here, a report of the monitoring program during the last six years before and after TPP construction and operation is presented. We also considered changes in ecosystems in the inside and outside of the lake. Overall, no hypoxic conditions were found during summer, even in the upper reach of the basin after TPP operation; however, there was a gradual but very rapid recovery in terms of species richness, abundance and biomass in Sihwa Lake. As a result, the overall macro