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Coral reefs

Hello!

We would love to introduce you to the topic of coral reefs and especially coral reef bleaching, as it is a greatly ignored but certainly significant topic. Have fun!

5 coral reef facts

1. The Great Barrier Reef is the largest living structure on the planet and is 2300 km long!
2. Less than 0.1% of the world's ocean surface is covered in coral reefs.
3. At least 25% of all marine animals live there.
4. Coral reefs are often known as the rainforests of the ocean.
5. In 1 square kilometre of coral reef, up to 35 tons of fish can be 'produced'.

The 5 biggest coral reefs in the world

1. Great Barrier Reef (near Australia)
2. Red Sea Coral Reef (near Egypt, Israel and Djibouti)
3. New Caledonia Reef (Pacific Ocean near New Caledonia)
4. The Mesoamerican Barrier Reef (near Mexico, Belize, Guatemala and Honduras)
5. Florida Reef (Atlantic Ocean/Gulf of Mexico near Florida)

What is coral?

Coral is actually made up of small animals called polyps, who are related to jellyfish and sea anemones. Multiple polyps join together to ensure that at least some of them survive. The coral works together with algae called Zooxanthellae. The algae photosynthesise and give some of its oxygen and sugar to the coral and the coral gives the algae carbon dioxide back in return. This is called a symbiotic relationship. The coral receives up to 90% of its food from the algae. The algae also give the coral its colour. 

Coral reef bleaching

Coral reef bleaching is a term that all of us have probably heard multiple times in the last year. In 2016 and 2017 there were two mass bleaching events back to back. And afterwards, the coral was white. But why?
Coral reef bleaching is a problem that all coral reefs face. When faced with conditions that are different from normal (for instance, warmer water temperatures), the coral expels the algae. This may sound like a silly thing to do, but it is self-defence. The coral hopes that the algae will drift to an area with better conditions. If it does not, it would die. The coral's only hope is that the conditions will go back to normal and the algae will return. In the meantime, the coral returns to its original colour, white. It does not die but will slowly starve until the algae returns. If the algae do not return fast enough, then the coral dies of starvation.
10% of all coral reefs have already died due to human-caused bleaching and another 60% are severely threatened. The main causes of bleaching are changes in the water conditions, mainly caused by climate change

Your Green World Blog Team💚


Sources:

Images:
Coral reef: This image, owned by Greg Goebel (on flickr.com), is licensed under CC BY-SA 2.0.
Bleached coral reef: This image, owned by ARC Centre of Excellence for Coral Reef Studies (on flickr.com), is licensed under CC BY-ND 2.0.

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