An Introduction to Coral

This is the first installment in a three-part blog series about Coral written by Jess; one of our previous Marine Biologists.

Coral reefs are my favourite places on the planet. I love everything about them: the vibrant colours, the intricate structures, and the endless amounts of creatures you meet. I was so completely bewildered with amazement the first time I saw this wondrous world, it was then that I knew I wanted to spend my life protecting these unearthly beings. But, how can I expect everyone else to love them as much as I do when most people don’t know what corals are, and how interesting they can be? So, here’s a brief insight into the creatures that bring me so much happiness.

Coral might look like a multicoloured rock, but it’s an animal. Actually, it’s thousands of tiny animals creating one huge colony of animals. Coral polyps are soft-bodied organisms, each only a few millimetres wide, and in the same family as anemones and jellyfish.  Coral reefs commence when a tiny 2-day-old polyp finds the perfect place to settle and spend its entire life, here it attaches to the rock on the sea floor and divides (or buds, if you want to be scientific) into thousands of clones.


Coral polyps hiding in the hard corallite vs coral polyp outside the corallite.

At the base is a hard limestone skeleton called a corallite, which forms the structure of coral reefs. It’s like a little protective cup that corals can shelter in. The corallites connect to one another, creating the colony that acts as a single organism. As colonies grow over hundreds and thousands of years, they join with other colonies and become coral reefs. Some of the reefs on planet earth today have been growing for over 50 million years.

Corals are very demanding in their environmental requirements. Water that is too salty or too hot will kill them. Nor can they grow at depths beyond the reach of sunlight because of their dependence upon single-celled algae that grow within their bodies. Residing within the coral’s tissues, the algae, called zooxanthellae (pronounced zoo-zan-thell-ee), are well protected and make use of the coral’s waste products for photosynthesis. The corals benefit, in turn, as the algae produce oxygen, remove the waste, and supply nutrients that corals need to grow, thrive, and build up the reef. This partnership is called symbiosis, an interaction between two organisms that’s advantageous for both partners (like the clownfish and anemone – see Cassie’s blog).  More than just a clever collaboration between some of the tiniest ocean animals and plants for 25 million years, this mutual exchange is the reason why coral reefs are the largest structures of biological origin on Earth.


So that’s a very brief introduction into the rocks that are actually thousands of tiny animal clones that house even tinier photosynthetic algae in beautiful partnerships that have been around for millions of years. Always remember how sensitive these creatures are, never snorkel wearing suncream because the chemicals kill the corals (wear a rash vest instead), always say no to plastic bags because these end up in the ocean and smother all the wildlife, and finally, be a climate change warrior and eat less meat. Fight global warming by doing as little as “Meatless Mondays” and help stop the mass coral bleaching that could completely wipe out these vital ecosystems.

By Jess Kalisiak

Posted in Experience, internship, Marine Biologist, Marine Conservation, Volunteer Programmes and tagged , , , , , , , , , , , , .

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