Florida's coral reefs came into existence 5,000 to 7,000 years ago when sea levels rose following the Wisconsin Ice Age. Reef growth is slow; estimates range from one to sixteen feet every 1,000 years.
Stony corals are the major reef architects. Polyps, the living portion of the coral, extract calcium from seawater and combine it with carbon dioxide to construct the elaborate limestone skeletons that form the reef backbone. Coral polyps are united into colonies. An individual colony grows one-half to seven inches a year, depending on the species. Corals start life as free-living larvae that later settle on the sea floor and develop into massive, sedentary limestone formations.
Though reef corals are classified as animals, there is, in fact, a complex of microscopic plants that lives within the animal tissues (a symbiotic relationship). The animals benefit from the energy that the plants provide through photosynthesis. The plants are protected within the coral tissues and gain nutrients from animal wastes. These tiny plants are called zooxanthellae and are responsible for much of the color seen in reef corals.