The Coral Reefs of the Florida Keys

The Coral Reefs in the Florida Keys

The Florida reef tract is the most extensive living coral reef system in North American waters and the third largest system in the world. The largest barrier reef is Australia's Great Barrier Reef and the second largest is the Belizian barrier reef. All of these reefs are created by a community of organisms which produce calcium carbonate (CaCO3). Together these coral animals use their calcium carbonate to build an underwater city over the course of thousands of years.

Calcium carbonate is produced by many marine plants and animals, including some species of algae and many marine invertebrates. These organisms use the calcium carbonate as a skeleton, either internally similar to a human skeleton or externally such as a snail shell. In any case, these skeletons of calcium carbonate mesh to form a rigid, wave resistant structure called a reef. When the primary reef-building organisms are corals of the phylogenetic order Scleractinia and certain algal species, the reef is called a coral reef.

Colonies of tiny anemone-like polyps are the living coral tissue. Within the tissue of most reef-building corals live small organisms that are capable of photosynthesizing or changing light energy into food. These organisms are called zooxanthellae, pronounced zo-zan-thel-ee. Although corals are carnivorous and feed on zooplankton, they receive much of their energy and oxygen as byproducts of zooxanthellae photosynthesis. The zooxanthellae also promote the rate of calcium carbonate production by the coral colony, thus, promoting growth. The relationship between coral colonies and zooxanthellae is called symbiosis. This is a mutual relationship between species in which one or both benefit. Symbiotic relationships are common among organisms living on coral reefs.

Coral reefs can be found in waters surrounding land masses that fit within a narrow range of physical parameters. Generally, reef-building corals are restricted to the tropics, the area between the Tropic of Cancer (23.5 degrees north latitude) and the Tropic of Capricorn (23.5 degrees south latitude). Tropical waters are generally warm, clear, low in nutrients, and have a stable temperature and salinity.  Ocean currents can alter the physical characteristics of an area reducing or expanding the area where reefs may develop. The Florida Keys is one example in which the warm waters of the Gulf Stream expand the range of corals north of the tropics. Info from NOAA website