Causes and countermeasures for coral reef bleaching

サンゴ礁、魚、海environment issues

Global warming The coral reef is often mentioned in the influence of the ocean.

This time, I would like to write about the cause and countermeasures for the coral reef bleaching phenomenon.

Causes and countermeasures for coral reef bleaching


Corals are often considered plants, but are classified as animals.

Small plants that live in coral tissues perform photosynthesis, giving color and nutrition to corals.

However, if the seawater temperature rises by 2°C due to global warming, the corals will lose this partner. And they lose their nutrition, become white, starve, and die.

Only 2℃? I think some people think so, but it is easy to understand if you replace them with people. As you can see, the temperature of the human body rises from 36 degrees Celsius to 38 degrees Celsius, which is 2 degrees Celsius.

Corals likewise increase seawater temperatures by 1°C and, if lasting for a month, can cause bleaching. If this continues for more than two months, the corals can die.

The bleached coral reefs are really beautiful, but dead.

For this reason, many corals are white on the warm Australian Great Barrier Reef.

Carbon dioxide is a cause of global warming and increases the acidity of the sea. The sea becomes weakly acidic, and corals are hampered by skeletal growth and become fragile.

Therefore, the acidification of the sea due to the increase in carbon dioxide, which causes global warming, also leads to the extinction of coral reefs.

Scientists attribute it to the rapid warming of the planet from greenhouse gases emitted by humans. According to the United Nations Intergovernmental Panel on Climate Change (IPCC), coral bleaching is the “widest and most significant impact” of global warming.

If a coral dies, many living creatures in it will also be extinct.

Coral bleaching can be catastrophic, which can wipe out the entire ecosystem.

World’s serious bleaching phenomenon


At the Great Barrier Reef, 1,000 km of coral reefs bleached between 2016 and 2017. In addition, by 2020, the southern end of the reef will be reached within about 1,500 miles (2,300 km) of the northern Torres Strait.

This is the third coral reef bleaching phenomenon in the last five years.

(Terry Hughes, Director of James Cook University ARC Center of Coral Reef Research Center)

It is 93% of all coral bleaching phenomena.

A dead coral reef was found in Samoa, USA. Half of the shallow coral reefs around the world are dead.

The rest will not last for 20 years.

CNN : Bleached coral reef

“The effects of climate change up to 2100 could wipe out most of the world’s coral reefs.”

A research team at the University of Hawaii at Manoa at the Marine Science Congress in February 2020. Announcement.

About 70-90% of the world’s coral reefs are projected to disappear within 20 years due to global warming, acidification and marine pollution of seawater.

Impact of coral reef bleaching


Coral reefs play a very important role and we enjoy many benefits.

Coral reefs inhabit 25% of the world’s marine life. It’s like the Amazon rainforest.

Several coral reefs provide homes for species not found anywhere else on earth.

It is often said that looking at the appearance of coral reefs reveals the environment of the sea.

Coral reefs also help protect cliffs and beaches from potential coastal erosion.

Corals can also be used for some types of drugs. Beautiful coral reefs help locals earn income from tourists.

Is there a future for coral reefs in this critical situation?

But there is hope.

Corals are elastic.

Australia has decided to spend 37.5 billion yen to protect the Great Barrier Reef.

In some countries, coral nurseries have been created to re-grow damaged coral reefs. But recovery of coral reefs can take decades.

Sunscreen ingredients harmful to coral reefs have been banned


According to non-profit academics, the UV-blocking components oxybenzone and octinoxate cause significant damage to the Hawaiian marine environment.

Studies have found that these chemicals cause bleaching phenomena by flowing into seawater through drainage from swimmer swimming and wastewater treatment plants and by immersing them in young corals.

According to a paper published in an academic journal in 2015, the amount of sunscreen that flows into coral reefs around the world reaches about 14,000 tons per year.

This bill will come into force in Hawaii on January 1, 2021.



We need to know what we need to protect.And knowing that, you should know what your children and their descendants should be doing on Earth.

I want to prevent future children from saying, “Why didn’t you do anything, even though you knew what the earth would be like with research data?”

Quotation: Netflix “Our Planet ~ Coastal Seas”


BBC “Coral Bleaching: What is it, how does it happen and how bad is it?” 9 April 2020

CNN “Great Barrier Reef suffers third mass bleaching event in five years” 7 April 2020 “Sunscreen ingredients harmful to coral reefs, passed a ban law, Hawaii,” May 2018