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South Florida Aquatic Environments

Coral Reefs

Spur and Groove Reef Formation
courtesy Florida Keys National Marine Sanctuary
spur and groove

Coral reef communities within Florida waters are categorized as:

Bank Reef Community

  • Located seaward from patch reefs
  • High species diversity
  • Characterized by spur and groove formation
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
© Eugene Weber, California Academy of Sciences

Sea Fan

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.

Bank Reef Scene
courtesy U.S. Geological Survey

Bank Reef

Plate Coral
© Eugene Weber, California Academy of Sciences

Plate Coral

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.

Rock beauty
© Bob Klemow

Rock beauty

Common inhabitants of the outer bank reefs include:

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.

© Luiz Rocha


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.

Moray at a Cleaning Station
© Jeremy Stafford-Deitsch