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
Réunion's coral reef Réunion's coral reef Réunion is an island located near the eastern coast of Madagascar in the Indian Ocean. Its coral reef covers a concentrated part of the western littoral. The coral reef is located between St Leu and St Gilles. It is more than long and ranges in width from in its northern part at St. Gilles to in the south. Since the island is close to the continental shelf, the sea becomes deep not far from the coast. The presence of nearby deeper ocean currents supports a rich biodiversity fauna and flora in the reef environment. Coral reefs are