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Types of Coral Reefs

 Fringing reefs are coral reefs that grow in shallow waters and border the coast closely or are separated from it by a narrow stretch of water. Fringing reefs consist of several zones that are characterized by their depth, the structure of the reef, and its plant and animal communities. 

Fringing reefs around Okinawa

Fringing reefs around Okinawa

Credit:NASA

 

These regions include the reef crest (the part of the reef the waves break over), the fore reef (the region of medium energy), and the spur and groove or buttress zone (the region of coral growth which includes rows of corals with sandy canyons or passages between each row).

 

Fringing reefs around Barbados
Fringing reefs around Barbados have declined over many decades although there are still submerged reefs off the west and southern coasts [STS051-72-95, 1993]

Apron reef – short reef resembling a fringing reef, but more sloped; extending out and downward from a point or peninsular shore

  Barrier reefs are reefs that are separated from land by a lagoon. These reefs grow parallel to the coast and are large and continuous. Barrier reefs also include regions of coral formation that include the zones found in fringing reefs along with patch reefs (small reefs), back reefs (the shoreward side of the reef), as well as bank reefs (reefs that occur on deep bottom irregularities).

 Barrier reefs also include reef flats (the are of the reef not exposed), the reef crest, which runs parallel to the coast and is protected from waves, and a coral terrace (a slope of sand with isolated coral peaks). These features are followed by another coral terrace and a vertical drop into deeper waters.

Australia’s The Great Barrier Reef arches over 2000 kilometers along the northeast coast of Australia.

Australia’s The Great Barrier Reef arches over 2000 kilometers along the northeast coast of Australia.

Credit:NASA

 

Patch reef – an isolated, often circular reef, usually within a lagoon or embayment

  • Located in shallow water 10-20' (3-6 m)
  • Outer edge ringed by sand
  • Dominated by large star and brain coral colonies

Ribbon reef – long, narrow, somewhat winding reef, usually associated with an atoll lagoon

The North West Cape is bordered by Australia's longest fringing reef, the Ningaloo Reef

The North West Cape is bordered by Australia's longest fringing reef, the Ningaloo Reef

Credit:NASA

 

Table reef – isolated reef, approaching an atoll type, but without a lagoon

 

Table reef

Credit: New England Aquarium

 

Bank Reef – Bank reefs are larger than patch reefs and are linear or semi-circular in outline

Bank Reef Scene 

Bank Reef Scene 

credit: NOAA

  • Located seaward from patch reefs
  • High species diversity
  • Characterized by spur and groove formation

 

 

 

Atolls in The Maldives Credit: NASA

 

Atolls in The Maldives Credit: NASA 

 

 Atolls are annular reefs that develop at or near the surface of the sea when islands that are surrounded by reefs subside.

 Atolls separate a central lagoon and are circular or sub-circular. There are two types of atolls: deep sea atolls that rise from deep sea and those found on the continental shelf.

View of Midway Atoll from Space Shuttle

View of Midway Atoll from Space Shuttle

 

  

Reef Relief founders Craig and DeeVon Quirolo retired from the grassroots organization last July, only to begin an effort to provide an online resource on coral reefs. Their new website provides all the award-winning educational tools, grassroots strategies, project reports and images of coral reefs assembled during their work over the past 23 years in the Florida Keys and throughout the Caribbean protecting coral reefs. You can find it at www.reefrelieffounders.com

 

 

 

credit: NOAA, NASA, Reef Check, UNEP, Reef Relief, Australian Government