Coral reefs in Japan's Wakayama Prefecture on brink of death

Tuesday , April 17, 2018 - 9:22 AM

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(c) 2018, The Japan News/Yomiuri.

TORKYO - The vast majority of coral reefs examined off Wakayama Prefecture - the world’s northernmost coral reef zone - are bleached and facing extinction, a recent survey by the Environment Ministry has found.

Coral bleaching, which leads to coral extinction, was observed at all six points the ministry surveyed. At five of the points, 85 percent to 95 percent of coral was found to be dead.

Lower sea temperatures are believed to be behind the bleaching. The falling temperatures are caused by the “great meandering” of the Kuroshio current that occurred for the first time in 12 years last autumn, as well as a cold wave this winter.

Organized by the ministry’s Tanabe Ranger Office, the survey was conducted in February and March by local divers and others in and around Tanabe Bay in the southern part of the prefecture.

Coral bleaching is a phenomenon in which plankton that live symbiotically with coral leave when the coral begins to be stressed by higher or lower sea temperatures. The phenomenon was observed in over 90 percent of the coral surveyed at all six points. Bleaching likely accelerated over the winter, as the phenomenon was observed on fewer than 5 percent of the coral at two examination points in December. The ranger office plans to continue fixed-point observations and monitor developments.

The average sea temperature in Tanabe Bay was 14.3 C (58 F) in January and 13.6 C (56 F) in February, about 3 C lower than the previous year, according to Kyoto University’s Shirahama Oceanographic Observatory.

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