Scientists warn of widespread coral bleaching in south Japan

TAKASHI SUGIMOTO Asahi Shimbun 13 Sep 16;

Coral bleaching is observed off Ishigakijima island in Okinawa Prefecture in August. (From the “coral map” website)

Coral bleaching has spread around islands in Okinawa and Kagoshima prefectures, threatening to inflict the worst damage to the tourist-attracting coral reefs in southern Japan since 1998, researchers said.

Prolonged coral bleaching, a phenomenon in which overly warm seawater and other factors cause corals to turn white, could end up wiping out large parts of the coral reefs, the researchers warn.

“Many corals could be lost,” said Hiroya Yamano, director of the Center for Environmental Biology and Ecosystem Studies at the National Institute for Environmental Studies.

Yamano and other researchers are calling on people around Japan to observe corals and send information about them to the “coral map” website ( The site is operated by an environmental nonprofit group and organizations of divers to determine the extent of the damage and develop countermeasures.

Yamano said he has received more than 20 reports since July on coral bleaching around at least five islands, including Yakushima in Kagoshima Prefecture and Taketomijima and Ishigakijima in Okinawa Prefecture.

Coral bleaching has been reported in a wider area in Japan this year than in 2007 and 2013, when bleaching was observed near only a limited number of islands.

The widest damage to Japanese coral reefs occurred in 1998, when the El Nino phenomenon caused seawater temperatures to rise.

According to the U.S. National Oceanic and Atmospheric Administration, water temperatures around the main island of Okinawa this summer are at the highest level since 2001, exceeding the warning level for coral bleaching.

If the corals die out, marine creatures would be negatively affected and tourism could decline in the surrounding areas.

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