壹岐島
Tsushima Reef, located in the bay between Tsushima and Iki Island, is the northernmost coral reef in the world, surpassing the Iki Island reef discovered in 2001. It is dominated by cool-tolerant stony or Scleractinian "Favia" corals but the observed settling of tropical "Acropora" coral is expected to provide an ongoing indicator for continuing global warming.