More than 70 percent of Japan's largest coral reef, located southeast of the archipelago, died in 2016 due to a rise in water temperatures, according to a study by Japan's Ministry of Environment.
The waters around the reef, located in front of Ishigaki island in Okinawa, recorded an average temperature two degrees higher than normal, leading to coral bleaching, says the report disseminated by public broadcaster NHK Wednesday.
The country's environment department examined the reef, that boasts over 70 coral species and is considered one of the oldest and largest in the northern hemisphere, between November and December last year, and the study concluded 70.1 percent of the corals had died of bleaching.
The latest figure shows a notable jump with respect to that registered between September and October, when it was established that 97 percent of the corals had undergone bleaching and 56 percent had died.
The ministry added sea temperatures in the region have dipped since autumn began, and that some corals have recovered, but warned more of them may die adding it remains unclear if the reef will recuperate.
El Niño, a weather phenomenon that causes sea surface temperatures to rise, has contributed to coral bleaching around the world this year, including some of the largest protected reefs in Australia, Thailand and Maldives.
Coral bleaching occurs when they are faced with constant and extreme changes of temperature, light and nutrients.
The process also puts at risk a large number of fish species that depend on the reefs for shelter and food.
If greenhouse gas emissions continue at the current level in the Indian and Pacific Oceans, fish stocks could decline between 10 to 30 percent by 2050, as compared to the 1970-2000 period, according to the International Union for Conservation of Nature.