Types of Caribbean reefs
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Types of Caribbean reefs

map of Caribbean region showing distribution of corals and mangroves
As in the rest of the world, coral reefs are found in the Caribbean Sea mostly between the lines of 22oN - 22oS latitudes, where annual water-surface temperatures are not less than 20oC (68oF).

There are several types of reefs in the Caribbean, as described in the sections below.





Corals are shown in red and
mangrove regions in olive green



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Fringing reef

 

photograph of fringing reef off the coast of Grand Cayman Island
photograph of fringing reef off the coast of Grand Cayman Island
Fringing reefs are the commonest type of reef in the Caribbean.  They project directly from the shore and commonly surround islands. They do best in areas where freshwater input is minimal and water clarity good.

Shown in these photographs are fringing reefs around the Cayman Islands.

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seahorse dive leader in BIOLOGY OF CARIBBEAN CORAL REEFS website photograph of elkhorn coral on fringing reef taken from a video

Some of the elkhorn corals on this fringing reef are in poor shape. Parts have been broken off, perhaps from hurricane damage, but notice the edges that appear to have been nibbled off by coral-eating fishes - likely parrotfishes - Grand Cayman Island 2007

NOTE Acropora palmata

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Barrier reef

 

photograph of barrier reef off the coast of Belize" width="660" height="300" class="alignLeft" /><br />         Although common in other parts of the world, such as Australia, there is only one barrier reef in the Carribean Sea. The Belize Barrier Reef is 250 km in length with a continental shelf extending out 10-32 km from the shore.</p>       <<        <tr>
Barrier reefs are linear formations separated from the land by a lagoon.  Most such reefs, like the ones in Belize and Australia, are not continuous; rather, are aggregations of many reefs of varying size and shape, separated by shallow lagoons.  The Belize Barrier Reef is 250 km in length with a continental shelf extending out 10-32 km from the shore.

Belizian barrier reef separated from
the shore by an extensive lagoon.
The reef is the thin wooded strip
along the top of the photo. The
cartoon shows a cross-section

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Atoll

 

photograph of Bora-Bora atoll in the south Pacific

Atolls take the general form of a ring that encircle a lagoon.  Most atolls are of the deep-sea type and in the Indo-Pacific region usually grow from the summits of submerged volcanoes.  Although hundreds of coral-reef atolls are present in the Indo-Pacific region, only a half dozen occur in the Caribbean: one each off Yucatan and Columbia, and the remainder off the coast of Belize.  These Caribbean types are mostly of the shelf form, so named because they occur in shallow waters of continental shelves.

 

Bora Bora, French Polynesia, a deep-sea
atoll reef at the stage of development
shown in the middle view in the panel below

 
drawing showing first stage in formation of an atoll
The deep-sea type of atoll often begins as a fringing reef around an emergent volcanic cone 
drawing showing mid-stage in formation of an atollIn the perfect circular form upward growth of coral matches subsidence of the volcanic cone drawing showing final stage in development of a coral atollThis combined with sea-level rise (18,000yr ago) eventually forms a coral ring with enclosed lagoon
 

photograph of Glover's Reef, Belize from above
In comparison, shelf-type atolls of the Caribbean had a different origin.  One idea is that they originated from fragments of tectonic plates that accumulated in shallow continental-shelf areas.  Coral growth on the edges of adjacent fragments created small islands of coral, sometimes contiguous, sometimes separated, with shallow sediment-filled lagoons in their centres.  This may explain the “unfinished” non-circular shapes of Caribbean atolls such as, for example,  the broken rhomboidal shape of Glover’s Reef.  Photograph courtesy Seahorse Dive Shop, Placencia, Belize.

 

 

Glover's Reef, Belize. The lagoon in this atoll is thought
to have been formed about 8500ybp along with rising
sea levels, and has been stable from about 5500ybp

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Patch reef

 


Patch reefs grow in lagoons behind barrier reefs or within atolls.  They sometimes originate on sand from a single boulder or rock outcropping.  On any reef the many sessile and sedentary invertebrates, such as corals, sponges, and sea anemones provide 3-dimensional habitats in which fishes and motile invertebrates find food and protection. Without the framework of invertebrates, the fishes would soon leave. Another name for such reefs is "bommies".

NOTE these 3 words are used commonly in BCCR. Their definitions are: sessile = attached, unable to move, like a sponge; sedentary = capable of movement, but usually stays put, like an anemone; motile = able to move about freely, like a crab, sea star, or fish

 

 

 

 

Patch reef in Little Cayman Island

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Stromatolite reef

 

photograh of a stromatolite reef in Exuma Cays, BahamasTropical marine stromatolite growths are more commonly known from writings of palaeobiologists and from a few spotty world occurrences, but since the advent of SCUBA they are popping up in accessible shallow areas of the Caribbean. These unusual growths represent a combination of sand and cyanobacteria (e.g., Schizothrix, one genus of blue-green algae). The organism initially grows in mat form on the sediment surface. Fine particles stick to their polysaccharide sheaths and are bound up in a consolidated sheet. The organisms abandon the old sheaths, grow upwards to the light, produce new sheaths and, slowly, layer by layer, the structure forms. Algae, invertebrates, and fishes later colonise the 3-dimensional structure. Littler & Littler 2001 Coral Reefs 19: 258; photograph courtesy the authors.


Stromatolites are one of the earliest photosynthesising
life forms, earliest fossils dating to 3.7 bya. The one
shown here is in the Exuma Cays, Bahamas

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