Japan's biggest coral reef is facing disaster from rising ocean temperature with the bulk of it having gone dead due to coral bleaching.

This was disclosed by the environment ministry of Japan, which said 70 percent of the corals in the Sekisei lagoon reef in Okinawa has been killed by bleaching and blamed the rising sea temperatures from global warming for the phenomenon.

Sekisei is famous as a popular diving spot spread in 400 sq. km (154 sq. mi).

Extremely Serious

Experts affirmed that coral bleaching has expanded to 90 percent of this Japanese coral reef. Media reports also reinforced it by noting that the plight of the reef at the southernmost reaches of Japan is "extremely serious."

The ministry updated that it conducted a survey of 35 locations in the lagoon in November 2015 and found 70.1 percent of the coral was dead. Now the color of dead corals has turned dark brown and are seen submerged under algae.

Coral bleaching follows when coral loses the algae that live within it from the effects of rising water temperatures and pollution. Coral gets its color from the algae which supplies it nutrients. When bleaching happens, coral loses the supply of food and turns white, and then bleaching hastens.

Effects Of Global Warming

The Japan Meteorological Agency said sea surface temperatures around Japan had been up by an average of 1.07 degrees Celsius in the past 100 years, which is double the global average warming rate.

It said that between June and August 2016, Okinawa island's southern part had experienced a temperature of 30.1 degrees Celsius, which was 1 to 2 degrees more than the highest average temperature recorded since 1982.

Process Of Coral Bleaching

According to some ministry officials, sea water temperatures have somewhat receded since autumn but there is no clarity when the reef is going to recover.

Coral bleaching is not confined to Japan alone though its corals are in serious jeopardy. Globally, coral bleaching is destroying precious coral reefs.

Scientists are blaming coral bleaching to the long-term trend of rising ocean temperatures with the damage exacerbated by the El Niño effect that started in 2015.

The Great Barrier Reef in Australia is also bearing the brunt of rising sea temperatures. Its faster bleaching has been highlighted in many studies.

One recent study that examined the patterns in warming and coral bleaching between 1985 and 2012 found that 97 percent of the sites it studied had warming trends with 60 percent showing severe conditions. The study was conducted by the National Oceanic and Atmospheric Research Administration.

It also noted that the frequency with which temperatures reached the threshold levels of bleaching had tripled during the period of study.

Bleaching as such does not spell the end of corals as they can still recover if the right conditions prevail. However, persisting warming patterns across the globe are worrying scientists that corals will not get the needed time to replenish.

Action Plan To Save Corals

According to sources, the Japanese environment ministry has already taken some action in restoring the region's coral reef ecosystem by instituting a panel in 2007 to work on the task.

The Sekisei lagoon had a severe bleaching in 1998, which was a severe El Niño year, and again in 2007.

The action points to replenish the coral reefs include the removal of crown-of-thorns starfish that feed on corals and curbing of water pollution from agricultural activities, according to Mari Yamazaki, an expert member of the Environment Ministry's Nature Conservation Bureau.