But this is not the case, as the thin sediment supports a wide variety of crabs, worms, brittle stars and other organisms, and the bedrock is home to a variety of soft corals, sponges and algae. Many fish, lobster and turtles commonly feed and find shelter in hardbottom areas, especially in the numerous solution holes that can be found there. The reefs themselves are made up of colonies comprising thousands of tiny coral animals, called polyps, that live in a very delicate and balanced environment. Corals are invertebrates belonging to the phylum Cnidaria, along with their close relatives, the jellyfish, anemones and hydroids. There are more than 90 different species of coral in the waters of the Florida Keys, generally categorized as being either hard or soft.
Hard corals form the massive structures of the reef.
Commonly seen types include the brain, elkhorn, staghorn, star and pillar corals. As coral polyps develop, they produce calcium carbonate. The excretion of this mineral by thousands of polyps, over hundreds of years, results in the large, hard reef structures that we see today. The colonies of soft corals, called gorgonians, contain more protein than minerals, and thus they can be seen swaying in the currents. Common soft corals in the Florida Keys include sea fans, whips, plumes and rods.