Corals and the reefs they build are complex ecosystems Bleaching is a complex process, and this often means that it is poorly explained and commonly misunderstood in the mainstream media. To understand coral bleaching, it is important first to understand some basic coral biology.

To many people’s great surprise, corals are not just a plant or a rock, they are actually living organisms – animals closely related to jellyfish and sea anemones. They belong to the phylum Cnidaria, which groups together animals with a central mouth surrounded by stinging tentacles. The tentacles are used to grasp microscopic food from the water column and direct it to the coral animals – or polyp’s – central mouth.  This, however is not their main feeding behaviour.

Corals form a very special relationship called a symbiosis with a microscopic algae called zooxanthallae. The zooxanthallae – being an algae – photosynthesises, harnessing sunlight to turn into energy to feed and give energy to the polyp animal, which in turn provides it a safe home.

When a coral is faced with any kind of stress – whether this be an increase in temperature, change in salinity, ultraviolet intensity, exposure at low tide, flushing of freshwater, even sunscreens or chemicals – the algae becomes toxic to the coral, and the animal expels it into the water column. At this stage, the coral not only loses a huge 90% of it’s energy intake, but also its colour – hence the term bleaching.

Hard corals such as the majority of those found in the Lady Musgrave Lagoon, rely on these algae for its energy, and it is also what gives the coral its colour in most cases. When it expels its algae, the coral does not immediately die. In fact, the coral can regain its algae and bounce back from the stress to completely recover if the stress is not prolonged and conditions become suitable once again.

The biggest challenge is when corals are faced with stress after stress after stress and do not have the time to recover in between negative impacts. We have the power to reduce these stresses to ensure corals have the best chance of building resilience and making a successful recovery after being faced with threats!

Our crew is always ready to answer all of your questions to ensure your Great Barrier Reef Experience is educational, inspiring, memorable, and the best it can be!

Join us in learning about coral biology and reef health with our Marine Biologist for a Day Experience.

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