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Coral reef communities within Florida waters are categorized as:

Hardbottom community. Photo courtesy NOAA
Hardbottom community. Photo courtesy NOAA
Gorgonian coral. Photo courtesy Florida Keys National Marine Sanctuary
Gorgonian coral. Photo courtesy Florida Keys National Marine Sanctuary

Hardbottom Community

Hardbottom reef communities are found close to shore over limestone rock covered by a thin sandy layer. Hardbottom communities have low species diversity, dominated by gorgonians, algae, sponges, and a few stony coral species. Hardbottom habitats provide important cover and feeding areas for many fish and invertebrates.

Hardbottom communities are often divided into two types:

Brain coral. Photo © Eugene Weber, California Academy of Sciences
Brain coral. Photo © Eugene Weber, California Academy of Sciences

Stony corals have adaptations, including a mucous layer used to removed sediments from their polyps, enabling them to survive in these communities.

These coral species include:

Mustard hill coral. Photo courtesy NOAA
Mustard hill coral. Photo courtesy NOAA

A variety of other animal species, including anemones, mollusks, crabs, seastars, sea cucumbers, spiny lobsters, and fish, are associated with hardbottom communities. Fish that forage in these areas include grunts (Haemulon spp.), snappers (Lutjanus spp.), groupers (Epinephelus spp.), and great barracudas (Spyraena barracuda). Tangs (Acanthurus coeruleus) and surgeonfish (Acanthurus bahianus) form large feeding schools over hard bottoms.

Gorgonians provide an increase in surface area for attachment of invertebrates including tunicates, anemones, mollusks, and worms.

Patch Reef Community

Blue tangs schooling over a patch reef. Photo courtesy U.S. Geological Survey
Blue tangs schooling over a patch reef. Photo courtesy U.S. Geological Survey
Arrow crab. Photo © Eugene Weber, California Academy of Sciences
Arrow crab. Photo © Eugene Weber, California Academy of Sciences


Patch reefs are located in shallow waters of 10-20 feet (3-6 m) in depth, within the Florida Reef Tract. The outer edge of each patch reef is surrounded by a halo of sand that extends out to adjacent seagrass beds. The width of this ring of sand is determined by the distance that herbivorous fish feel is within safe foraging range from the reef. Each patch reef differs in size, development, and species residing on them.

Star coral (Montastraea annularis) polyps. Photo © Mark Younger
Star coral (Montastraea annularis) polyps. Photo © Mark Younger

The patch reef originates with a coral larva settling out of the plankton onto a hard surface for attachment. It develops into a moderate-sized coral colony over time. Eventually the coral dies, perhaps from storm or predator damage, leaving behind the calcium carbonate skeleton upon which more coral larvae can settle. This continues for hundreds of years with the reef expanding upwards, towards the water’s surface. As the reef reaches the surface, it will begin growing outward rather than upward.

Large colonies of star and brain corals (Montastraea annularis, Siderastrea siderea, and Diploriaspp.) form the base of many patch reefs, with smaller coral species settling on any exposed dead coral. Boring sponges, worms, and mollusks excavate through the coral skeleton, forming crevices that provide refuge for fish and invertebrates. Over time, the underlying foundation of the reef weakens resulting in the collapse of the structure.

Reef fish commonly found along the top of patch reefs include:

Atlantic damselfish (Chromis limbatus). Photo © David Snyder
Atlantic damselfish (Chromis limbatus). Photo © David Snyder
Redband parrotfish (Sparisome aurofrenatum). Photo © Bob Klemow
Redband parrotfish (Sparisome aurofrenatum). Photo © Bob Klemow


Among the coral heads and branching corals are:

Tomtate (Haemulon aurolineatum). Photo courtesy NOAA
Tomtate (Haemulon aurolineatum). Photo courtesy NOAA
Caesar grunt (Haemulon aurolineatum). Photo © David Snyder
Caesar grunt (Haemulon aurolineatum). Photo © David Snyder


Trumpetfish (Aulostomus maculatus) and filefish can be observed standing vertically among gorgonian branches. Larger predatory fish including grouper (Epinephelus spp.), snapper (Lutjanus spp.), bar jack (Caranx ruber), and great barracuda (Sphyraena barracuda) search for prey in the water above the reef formation.

Fringed filefish. Photo © David Snyder
Fringed filefish. Photo © David Snyder
Twospot cardinalfish (Apogon pseudomaculatus). Photo © David Snyder
Twospot cardinalfish (Apogon pseudomaculatus). Photo © David Snyder


Bank Reef Community

Bank reef scene. Photo courtesy U.S. Geological Survey
Bank reef scene. Photo courtesy U.S. Geological Survey

Bank reefs form an elongate, broken arc from Miami south along the Florida Keys to the Dry Tortugas. Located further toward the sea than the patch reefs of nearshore environments, bank reefs are significantly larger than patch reefs and are common dive and snorkel destinations.

Sea fan. Photo © Eugene Weber, California Academy of Sciences
Sea fan. Photo © Eugene Weber, California Academy of Sciences
Fire coral (Hydrozoan). Photo courtesy NOAA
Fire coral (Hydrozoan). Photo courtesy NOAA


On the inshore side of the bank reef is the reef flat. This area consists of broken coral skeletons and coralline algae. Seaward from the reef flat is the spur and groove formation consisting of low ridges of corals (spurs) separated by sandy bottom channels (grooves). Within shallow areas, the bottom substrate is colonized by fire corals and zoanthids. With increase of water depth to five or six feet (1.5-1.8 m), elkhorn (Acropora palmata), star (Montastraea annularis), and brain corals (Diploria spp.) dominate the surface of the reef. Sea fans, seawhips, and sea plumes are also common in this area. The sand grooves running between the spurs consist primarily of shells and fragments of coral and algae that make up the coarse white limestone sand. These grooves are habitat for many invertebrates which remain hidden in the sand during the day, sneaking out under the cover of night to search for food.

Further out from the spur and groove zone is the forereef zone. This area, dominated by star coral (Montastraea annularis), is inhabited by a variety of benthic organisms. The reef then slopes deeper into the sea where light becomes a limiting factor. At these depths, corals adapt to lower light levels by growing in flat, plate-like formations. At depth further increases, the reef drops off rapidly into the depths. Sunlight gradually disappears, resulting in a community of sponges and non-reef building corals.

Common inhabitants of the outer bank reefs include:

Queen parrotfish (Scarus vetula). Photo courtesy NOAA
Queen parrotfish (Scarus vetula). Photo courtesy NOAA
Goatfish (Scarus vetula). Photo courtesy NOAA
Goatfish (Scarus vetula). Photo courtesy NOAA


Fish frequent the reef during different times of the day. Many fish leave the protection of the reef at night to venture out to the nearby seagrass beds in search of food while other species, such as the parrotfish, settle down for the night within the reef structure. Parrotfish build a mucus cocoon that surrounds them at night while they sleep. If the cocoon is disturbed, the fish immediately awakens and dashes off, escaping any potential predators.

Moray at a cleaning station. Photo © Jeremy Stafford-Deitsch
Moray at a cleaning station. Photo © Jeremy Stafford-Deitsch
Cleaner shrimp. Photo © Mark Younger
Cleaner shrimp. Photo © Mark Younger


Cleaning stations are maintained by a number of small organisms including wrasses, gobies, and small shrimp. Larger fish visit this station to have their teeth cleaned and external parasites removed. These fish signal through body movements and postures, letting the cleaners know that they are ready to have their mouths and gill chambers cleaned. This relationship benefits the visiting fish as well as the cleaners.


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