One of the most fascinating and yet least known ecosystems in the world, the Coral Reefs, are home to an incredible diversity of organisms. Because of the need for warm water and a constant flow of ocean current, coral reefs are mostly present between the tropic of Cancer and the tropic of Capricorn. The third requirement for a coral reef is shallow water so that the symbiotic algae in the hard coral can survive. These unicellular algae need sunlight to produce nutrients through photosynthesis in the same way plants do.

Coral reefs are generally categorized into three groups: Fringing Reef, Barrier Reef and Atoll according to there general shape and inhabitants. Do to the interruption in the formation of the recent reefs by glaciation in the Atlantic-Caribbean tropical waters, a forth designation has be termed Bank/Barrier Reef for the reefs in the Caribbean area. The lagoons are mush sallower and the reefs are formed much closer to the shore then barrier reefs. Since this is the type of coral reef present in the Florida Keys, this page will mainly focus on the Bank/Barrier Reef.

The closest terrestrial ecosystem to coral reefs is the tropical rain forest for two reasons. The first is tremendous biodiversity. Similar to a tropical rain forest coral reefs have an exceptional amount of organisms. The second is that every little bit of space is used and nothing goes to waste. Every organism in a coral reef has it’s own niche, weather it be at the bottom of the coral, the top of the coral or simply somewhere in the coral.

The most important member(s) of coral reefs are coral polyps (animals that look like upside down jellyfish). Unfortanantly coral polyps could not build reefs alone, they need the help of zooxanthellae. As mentioned before these two organisms live together symbiotically.

Zooxanthellae produce about 85% of the nutrients used by their symbiotic coral polyps. Without the zooxanthellae some species of coral would die. On the other hand the coral provides a safe place for the algae to live with out risk of being eaten. This kind of symbiosis is called mutualism, where both species benefit from the relationship.

Zooxanthellae also help the coral polyps to make calcium carbonate from the salty water so that the coral can grow. Reefs grow seaward and upwards by adding layer upon layer of coral. This building of the reef by adding layers leaves many holes and crevices providing shelter for crustaceans and smaller fish. While coral reefs only take up 2% of the ocean floor about 25% of all ocean species call this ecosystem home.