Coral reefs are known as the "rainforests of the seas", and looking at all of the different colours, it isn't difficult to see why.
What is coral?
Corals are made up of many small organisms that work together as a single organism.
Their colours come from algae that lives inside the corals; the coral's tough outer shell provides the algae with protection, and in return it provides the coral with energy.
Some coral reefs have been growing for over 50 million years.
Why are they important?
They are one of the most diverse habitats in the world, with over 25% of all marine species living in or around them. Many fish species use them as nurseries where they young can feed and grow with shelter from their predators.
They help protect shorelines from large waves during storms.
Millions of people rely on the fish caught in or around coral reefs.
They provide people with income from tourism as people travel from all over the world to see coral reefs.
What threats do they face?
Coral bleaching: When the water's temperature rises, the algae is forced out of the coral, causing it to loose its colour and main source of food; this is known as coral bleaching. Corals are still alive when they bleach, but they are at risk of starving and eventually dying.
Ocean acidification: The ocean absorbs carbon dioxide from the air, which increases the acidity of the water. This makes it harder for corals to build their exoskeletons (their hard shells).
Tourism: Coral reefs can be damaged by scuba-divers who touch the corals while diving.
Pollution: They are very sensitive to their environment, and can be harmed by chemicals polluting the water.
What are the main solutions?
Coral reefs are under serious threat; the world has lost 20% of its coral, and it is likely that many reefs have already been irreversibly damaged, but there are some ways conservationists are protecting them:
Coral transplants: Scientists transplanted hundreds of nursery-grown coral fragments into the Great Barrier Reef, Australia.
Protected areas: Corals survive better in areas protected from fishing.
Genetics: Scientists may be able to restore reefs more heat-tolerant coral.
The best solution is drastically reducing greenhouse gas emissions and reducing global warming, because otherwise ocean temperatures and acidity will just continue to rise and rise, and there's a limit to how much help the strategies above can give the corals. Over the last 400 million years, corals have adapted to earth's changing temperatures; but until recently, the changes were always very slow, giving the coral enough time to evolve. Now, climate change is threatening their survival.
What can you do?
If you decide to visit one of the coral reefs, make sure you dive or snorkel responsibly; avoid touching the coral, as that damages them. If you're swimming near a coral reef, try to use reef-friendly sun-cream, because some of the chemicals in ordinary sun-cream can harm or even kill coral.
Dispose of waste responsibly, especially plastic. If you see plastic or other litter on a beach, think about picking it up and putting it in a recycling bin.
Try to mostly buy organic food, because pesticides and fertilizers on fields get washed into rivers, and eventually carried out to oceans and seas.
Use environmentally-friendly transport methods to reduce greenhouse gas emissions. Where possible walk, cycle, car share or use public transport.
Aquariums: Avoid buying coral for aquariums, and if you buy marine aquarium fish, make sure they are from a sustainable source.
Want to find out more?
Have a look at these websites:
This article by National Geographic about coral reefs and the threats they face.
This National Geographic article about coral.
Read information about coral reefs on National Geographic. It includes a video showing what coral bleaching looks like.
Can new science save coral reefs? Read this article on National Geographic.
How can you help?
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