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Coral Reef Knowledge

The corals of Queensland's reefs provide divers and snorkellers with a display of colour, shape and movement that is replicated nowhere else in the world. Here are 7 facts to help you understand our underwater world better.

1. The Great Barrier Reef hosts one third of the world's coral species

More than 400 (or one-third) of the world's coral species can be found in the Great Barrier Reef World Heritage Area.

Amazingly what is seen is just a thin covering of living coral believed to be about 8000-years-old, which has built up on top of dead corals and algae over the past 500,000 years.

2. Hard coral grows up to 1.5cm per year

To the untrained eye, hard coral might look like a colourful piece of rock. The truth is this backbone of the reef is growing and constantly adapting to the demands of the environment around it. 

Hard corals are formed from a limestone-covered polyp organism dividing into two leaving behind its hard outer skeleton when a new one is formed. Growth is generally slow, especially in the first few years, with most hard corals growing at a rate of 1-1.5cm a year.

3. The reef is a place to call home

Not only is it beautiful to watch, the reef also provides a permanent home for a wide range of creatures.

Exotic coral structures shaped like staghorns, tabletops, fans and brains create a habitat for a myriad of fishes, enchinoderms, molluscs and microoganisms such as algae and plankton.

4. Everything exists in symbiosis

Like life in general, good relationships are the key to survival. And soft corals and anemones make an important contribution to this delicately-balanced ecosystem.

Most soft coral species have a symbiotic relationship with microscopic single-celled algae that live inside their tissues, transferring food to the host coral.This very important relationship depends on clear warm shallow waters with temperatures of above 18° C. Dramatic temperature variations can result in the coral expelling the algae, resulting in coral death or coral bleaching.

5. Full-moon is "sexy time" for corals

Coral spawning or reproduction is a nocturnal phenomenon that happens annually in late spring or early summer. Also known as "sex on the reef", egg-engorged corals simultaneously release masses of pretty pink eggs and sperm into the sea to become free-floating larvae.

While its timing is thought to be related to the water temperature and phases of the moon, it is impossible to predict exactly when it will occur. It usually occurs with the lunar month and dates vary, usually 3-4 days after the full moon. 

6. The reef's worst natural predator is a starfish

Apart from climate change and human impact, there's one predator known to keep corals up at night. Despite its harmless sounding name, The Crown of Thorns Starfish is the boogey man of the reef. 

While this species is notorious for stripping reefs of nearly all living coral, fortunately new corals are generally able to re-grow after an outbreak.

7. Seagrass beds are the pastures of the reef

Most commonly seen as the nutrition-rich wrapping of your sushi roll, the reef's 500 seaweed and algae species provide feeding grounds for a number of creatures. These ocean pastures are home to a quarter of all known seagrass species and also important habitats for dugongs and endangered sea turtles.

While we still don't know much about these habitats, their contribution to the preservation and biodiversity of the reef is without question.



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