The Great Barrier reef, a series of coral reefs along Queensland's coast, is the largest structure created by organisms. Where geology and tides are favorable, coral reefs are created by innumerable minute organisms, animal and vegetable corals and the microorganisms they host. The islands are the richest maritime biotope for fish and other aquatic creatures. It all changes quickly with the tides, the season and shaping forces such as erosion.
Most of the Grat barrier Reef are island behind the corals. They to have a diverse wildlife, dependent on their relatively rapid life cycle, height, arrival of 'immigrants', suitability for egg laying etcetera.
However fascinating the reefs themselves may be, far more species depend on the environment they create outside, both on island soil and in deep sea. Each occurs in Australia and its Indian Ocean waters in abundant number and variety.