Coral

At first sight, coral may be believed to be just a rock on the seabed, but in actual fact it is something more fascinating. It is actually created by living animals called polyps that produce a chalky, limestone skeleton as they expand. Coral can be seen to expand when the polyps multiply and divide in a technique known as budding.



Polyps take their nourishment from planktonic4 prey, including simple single-celled algae5 called zooxanthellae6(pronounced zoo-zan-thelly). Coral that lives off zooxanthellae expands faster than that which doesn't. Coral comes in various colours, shapes and sizes. Some agglomerations create features such as bommies7 and drop-off cliffs8. Coral displays many vibrant colours as a result of live coral and its algae that can reach an age of hundreds of years. To see these wonderful colours it is best to view the coral at night using a halogen lamp shone from above. Every year, around the full moon in November, the sea spreading up the reef from Lady Elliot Island in the south gradually turns pink. This is due to 135 species of hard coral releasing their eggs and sperm for fertilisation. It takes about two weeks for coral to reproduce before the water appears clean again.