President Lee Myung-bak marked the start of operation at the world's largest tidal power plant in South Korea on Monday, calling it a "symbol" of his trademark "low-carbon, green growth" policy of seeking clean energy sources. The power plant at the artificial sea-water Lake Shihwa on the west coast near Seoul began partial operation early this month after nearly seven years of construction. Six of the 10 generators have been running since Aug. 3, and the others will go into operation in stages after test-running.