Boulder brain coral (Colpophyllia natans) is one of over 40 stony coral species that have been identified on southeast Florida reefs.
Photo: Dave Gilliam, PhD.
Bent Sea Rods (Plexaura flexuosa), like the one pictured here, are one of many soft coral species (also called gorgonians) found on southeast Florida reefs.
Photo: Eric Engler
Coral reefs are an amazing expression of nature. These living reef structures provide shelter, food and breeding grounds for numerous marine plants and animals. Coral reefs are the basis for a dynamic ecosystem with tremendous biodiversity. For example, most of Florida's sport fish species and many other marine animals spend significant parts of their lives around coral reefs.
Florida's coral reefs began forming 5,000 to 7,000 years ago when sea levels rose following the last Ice Age. Reef growth is extremely slow; an individual colony may grow only ½ inch to 7 inches (1 cm to 18 cm) a year, depending on the species. Corals take on many shapes. In southeast Florida, octocorals (commonly known as seafans, sea whips, etc.) and stony corals are common. In stony corals, each animal (called a polyp) extracts calcium from seawater and combines it with carbon dioxide to construct the elaborate limestone skeletons that form the reef backbone.
Although corals may look like rocks or plants, they are actually animals, closely related to another marine creature — the jellyfish! Polyps have an important symbiotic relationship with microscopic, single-celled plants called zooxanthellae that live within the animal tissues. The animals benefit from the energy that the plants provide through photosynthesis. The zooxanthellae are protected by the external coral skeleton and gain nutrients from the polyp's wastes.
Shallow coral reef development can only happen in areas that provide a solid structure for attachment, clear water low in excess nutrients like phosphorous and nitrogen, warm water temperatures, and moderate wave action to disperse wastes and bring oxygen and plankton to the reef. Florida's offshore waters have these characteristics and support shallow water reefs.
The reefs in southeast Florida are the northernmost in the Florida reef tract, which extends from the Dry Tortugas and Florida Keys in the south to Martin County in the north. Generally, the reefs in southeast Florida occur in three parallel lines extending north from Miami-Dade County, changing to more isolated patch reefs in Martin County. Different reef organisms characterize the type of habitats found along southeast Florida's reefs, typically transitioning from a cover of algae and small octocorals nearshore to numerous octocorals and varied stony coral populations at the outer reefs. The various reef architectural and compositional components create an environment that is ecologically diverse and productive: one that supports all of the other aquatic plants and animals that make southeast Florida reefs their home.