How are coral reefs made or developed?
Coral reefs are composed mainly of calcium carbonate, which is produced by corals (phylum Cnidaria, class Anthozoa, order Madreporaria = Scleratinia) with small additions from calcareous algae and other calcium carbonate secreting organisms. Coral is found throughout the world, but reef forming coral (hermatypic coral) are found only in tropical waters. Hermatypic coral grow by continually secreting calcium carbonate to its skeleton. It is the continual deposition of calcium carbonate that builds a coral reef. Corals are living animals that feed by using tentacles containing stinging cells (nematocysts) that catch planktonic prey. Hermatypic coral have algal symbionts that live within their tissues called zooanthellae. Zooanthellae is extremely important in the deposition of calcium carbonate. The organic compounds produced by the zooanthellae are used as food for the coral. Without sunlight, the zooanthellae cannot photosynthesize and the coral does not grow. If lack of light persists
