Coral reef A fringing reef forms around an extinct volcanic island as the island and ocean floor subsides. As the subsidence continues, the fringing reef becomes a barrier reef and ultimately an atoll reef. Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in the tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide. Where the level of the underlying earth allows, the corals grow around the coast
Coringa-Herald National Nature Reserve Coringa-Herald National Nature Reserve Coringa-Herald National Nature Reserve is a former nature reserve in Australia’s Coral Sea Islands Territory that was incorporated into the new Coral Sea Commonwealth Marine Reserve in December 2012. The former nature reserve together with the Lihou Reef National Nature Reserve is part of the Coral Sea Reserves Ramsar Site. Its extent is also within the Coringa-Herald Reefs Important Bird Area. The reserve lies to the east of the Great Barrier Reef and covers an area of 8,860 km, most of which is open water. It contains three pairs of islets and cays, the Herald Cays,