About the event
Brain coral, Wikipedia, Public Domain
Corals: weird, wonderful, beautiful. Can we save them?
Firstly, what is the problem, why are corals dying? It’s the issue on everyone’s mind (no not CoViD-19, corals can’t get that, the other one…) – Climate change.
As humans continue to create greenhouse gases, the world, and particularly, the oceans, are bearing the brunt of the negative impacts. The top few metres of the oceans store as much heat as all of the earth’s atmosphere. It is usually their role to absorb and distribute heat around the earth. While we’re heating up the atmosphere, the oceans are absorbing a lot of this heat, meaning that the oceans are heating up much quicker than the air.
For some animals this warming water isn’t a problem, they can swim to an area where it’s a little cooler. But for corals, animals (yes, animals, not plants!) that are rooted where they are, they can’t just up and move somewhere more suitable.
When you think of coral, you probably think of the beautiful bright coloured corals that make up a reef. These are just one kind of coral, you can also get corals that live in very deep dark waters. The corals that you’ll see growing in reefs aren’t just one animal, they are colonies of lots of animals called polyps.
The polyps grow and build up a skeleton of calcium carbonate, giving them a structure and allowing them to get really big and develop into whole reefs.
Shallow water corals often have polyps that have stinging tentacles that allow them to catch plankton and even small fish to eat! But the most common way they obtain food is very special.
Most corals get their energy and food using little in-house factories, called zooxanthellae. Zooxanthellae are a kind of algae that live in harmony with the corals, inside their tissues, and use photosynthesis (just like plants) to make energy and food for the corals.
The zooxanthellae come in all kinds of beautiful colours, and are why corals look so bright and beautiful. Without the zooxanthellae corals wouldn’t have enough food, and would lose their bright colours, turning white.
Healthy shallow reef by Toby Hudson - Own work, CC BY-SA 3.0
This is what we call coral bleaching. Zooxanthellaeare very sensitive to ocean temperatures, if they get too hot, they will leave the corals to find colder waters. Without the zooxanthellae, and therefore the bright colours, the corals look like eerie ghost versions of themselves, and if the temperatures don’t return to normal, the food factories will never return to the corals, leaving them to starve.