Photography provided by Brilliant Studios
Corals live in a house made of calcium carbonate (limestone) which they make by removing calcium and carbonic acid from the water. Limestone is a white stone. Corals, like their relatives, jellyfish, have clear, transparent bodies. So why do we see so many beautifully colored corals on a coral reef? It’s because of the zooxanthellae that live inside the coral polyp’s body.
Zooxanthellae are microalgae that have a symbiotic relationship with the coral. The algae gets a safe place to live and make food for itself and the coral polyp via photosynthesis. The coral polyp gets a great deal of its food from the zooxanthellae. But the zooxanthellae are a bit fussy about where they live. If the water temperature gets too warm or the water quality deteriorates, the zooxanthellae get stressed and start producing chemicals that the coral polyps don’t like. So the polyps eject the zooxanthellae, leaving just their transparent body against their white limestone home. This is coral bleaching. It is just the loss of the zooxanthellae.
This is a bad situation for the coral polyps. Although they can feed themselves by grabbing plankton that is drifting by in the water with their tentacles, they can’t feed themselves enough to survive for long. So if the water temperature stays too warm for too long or the water quality remains bad for too long, the coral polyp will die. But if the water quality or temperature returns to normal fairly quickly, the zooxanthellae will return and coral will survive.
This is why rising ocean temperatures are such a threat to coral reefs. It can result in large scale bleaching events. This has already happened on a global scale several times over the last three decades – in 1998, 2010 and again in 2015.
Coral Bleaching in Turks and Caicos
Luckily during the most recent bleaching event, the TCI reefs had some bleaching, but not as severe as a lot of other areas.