Definition: The marine coral reef biome comprises constructional wave-resistant entities which are primarily built by corals and are often cemented together. The growth of these structures is aided by zooxanthellae, algae that are symbiotic with the reef-building corals.
Definition: An oceanic island, often having a characteristic ring-like shape surrounding a lagoon. Atolls are formed when coral reef grows around a volcanic island that later subsides into the ocean.
