A few of the many organisms in the Great Barrier Reef...
The Great Barrier reef has the most marine diversity in the world with 450 types of coral, 1500 types of fish, and 4000 types of molluscs. There are more different types of animals in the Great Barrier Reef than in any other place in the world. There are even more types of fish in some places of the reef than there is in the entire Caribbean Ocean. Coral also rely on many biotic and abiotic factors to keep them healthy and functional.
Information from Australia's Great Barrier Reef Marine Park Authority