Japans largest coral reef is under severe stress, according to a recent survey conducted by the countrys Environment Ministry. More than 90 percent of the corals in Sekiseishoko reef, located in the Ryukyu Islands near Okinawa, were discovered to be at least partially bleached when surveyed in November and December. About 70 percent of the reefs living corals were found to have died .

Rising ocean temperatures have been pinpointed as the main culprit for the reefs decline: Water temperatures in the region were 1 to 2 degrees Celsius higher than normal last summer.

Experts say the current bleaching event is the worst the reef has experienced in recorded history.