Coral reefs bleaching: impact of global warming on corals

12 June 2023 | Protect the environment

The bleaching episodes of coral reefs follow and repeat each other more and more throughout the world. Every ocean is touched. It’s only, neither more nor less, the impact of global warming that corals fully undergo. Besides, what is it exactly when we’re talking about corals bleaching? 

The impact of global warming on corals: bleaching phenomenon.

 When a coral is about to die, we say that he bleaches. We’re talking about bleaching coral. But when a coral bleaches, it doesn’t have to be condemned yet. Here’s why. 

Corals are living animals in symbiose with seaweed called zooxanthellae, as explained in our article definition of coral reefs. In fact, these animals also called polyps, are feeding thanks to nutrients given by the zooxanthellae and change of color based on this one. Based on the type, they can take a yellow, brown, red, or close to white color. 

 However, the variation of oceanic conditions (acidity, temperature) has an impact on corals. Indeed, a recurrent increase, a water more acid and zooxanthellae will act like “agressor” on polyps. They will damage on polyps which, to defend themselves, will expulse this tiny seaweed, yet essentially. 

 Thus, the expelled zooxanthellae, it can’t allow anymore to carry out the photosynthesis, neither to bring some nutrients or its color to the coral: the zooxanthellae doesn’t bring anymore pigments that color it and become immaculate white. 

This is why we’re saying it bleaches. 

The coral, living too much time without zooxanthellae, is going to die of starvation or of disease. Then, once dead, it starts to be recovered of invasive seaweeds. 

Nevertheless, if oceanic conditions return to the “normal”, zooxanthellae can come back to colonize polyps! 

Bleaching causes

Coral reefs are deteriorating. Indeed, according to a report of the Global Coral Reef Monitoring Network went out the 5th of October 2021, between 2009 and 2018, 14% of corals of the planet disappeared. This is equal to a “quantity more important than all the coral living in Australia”. 

Inside the most important threats we find: 

  •     Sea level rise (slowed by zooxanthellae photosynthesis);
  •     The mass tourism (trampling, solar cream, etc.);
  •     Industrial fishing, overfishing;
  •     Increasing of temperatures and ocean acidification (mostly due to the increasing of the carbon concentration in the atmosphere);
  •     Different types of pollution (spills of toxic products, plastic). 

 The common denominator being mostly: carbon dioxide. 

We present the causes in detail in our article treating causes of coral reef bleaching.


 Bleaching causes are many. They are from anthropogenic origin or not! 

  •     Spill of wastewater;
  •     Plastic;
  •     Rising sea level;
  •     Storms, hurricanes;
  •     Etc. 

 We’re saying a coral “bleaches” when it expels the seaweed with which it lives in symbiose. This last expelled, it’s no longer in capacity to give it oxygen, a part of the food and its original color: it bleaches and weakens. 

 Nevertheless, the seaweed can come back to colonize the coral if oceanic conditions are becoming mild again. Here’s why it’s important to reduce aggressions that coral reefs undergo. 

How Greenoco can help to protect corals? 

 Greenoco helps his clients to reduce his digital carbon footprint and tend to a better digital sobriety. By reusing carbon audits of websites, and by identifying the optimizations allowing to reduce them from 10 to 70% depending on the sites, we’re reducing together causes of sea acidification, and the jeopardizing of corals.

We’re not advocating internet suppression, and of all that it brings (you might not know the impact of carbon emissions on corals otherwise…). But we’re developing solutions allowing to measure the impact, and enabling companies and organizations to develop digital tools that are eco-responsible. 

 To realize a test of carbon emissions of your website, test our online solution. And for a complete carbon audit of your website, contact us for a free quote. 

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