Reef-building corals may perish by end of 21st century


Reef-building corals may perish by the end of the century if carbon dioxide emissions continue to acidify seawater, a Japanese research team announced Monday.

The team, led by Shihori Inoue of the University of Tokyo, clarified adverse effects of the carbon-caused oceanic acidification on coral-reef formation after years of field surveys in volcanically acidified waters around Iwotorishima, an island in Okinawa, and a coral culture experiment in a laboratory at the University of the Ryukyus in Okinawa.

As oceanic acidification progresses, hard corals, which form coral reefs, decrease while soft corals, which do not form rocklike skeletons, increase, the team said in a report.

The oceanic acidity increases as carbon dioxide emitted through various industrial activities dissolves in seawater. Acidified seawater melts coral skeletons made of calcium carbonate.

Soft corals withstand acid better than hard corals because they have only tiny bone fragments covered with fleshy tissue. But they cannot create reefs that provide habitats for a variety of creatures or act as natural breakwaters.