Adaptations to life in the marine environment


Coral Reefs

Location of the Coral Reefs

Coral reefs can be found in 109 countries throughout the world (see figure 1 below) – primarily located within the Tropic of Capricorn and the Tropic of Cancer, between 20o North and 20o South of the equator – the Indo-Pacific, the Western Atlantic and the Red Sea. (Reef Relief, May 2009)

The Indo-Pacific region is the largest and richest assemblage of coral reefs and stretches from southeast Asia through Polynesia and Australia, heading eastwards across the Indian Ocean and Africa. (Reef Relief, May 2009)

The Western Atlantic region (featured in blue in the figure above) is located from Florida to Brazil and includes Bermuda, the Bahamas, the Caribbean, Belze and the Gulf of Mexico. The Red Sea, located between Africa and Saudi Arabia as indicated in red in the figure above, is the smallest region. (Reef Relief, May 2009)

Characteristics of the Coral Reef

Coral reefs were first formed about 500 millions years ago and are the largest natural structure in the world. The Great Barrier Reef alone measures more than 1,250 miles/2,013 km long and as much as 150 miles/242 km wide in some places and was formed about 500,000 ago with its present structure being around 8,000 years old. (Reef Ecology, May 2009)

They are the most diverse biological marine ecosystem on our planet. Thousands of seemingly alien life forms of a multitude of bright colours and ever changing patterns live within the coral reef. The coral reef support over 4,000 species of fishes throughout the tropics and is also the only place that has examples of nearly every group of organisms which represent a billion years of evolution. (Reef Ecology, May 2009)

Over thousands of years, thin plates of calcium carbonate are secreted by billions of soft bodied animals called coral polyps that consist of a tube and an oral disc or mouth surrounded by tentacles that help catch passing plankton. This secretion takes years to grow just one inch of coral that can grow up to a foot in length. By living on top of the limestone remains of former colonies, the polyps help create massive reefs, the formation of which can be seen from outer space. (Reef Relief, May 2009)

Coral generally gets it colour from the algae zooxanthellae. This algae photosynthesises carbon dioxide that gives off oxygen which is used by the coral polyps. (Reef Ecology, May 2009)

Corals live on the ocean bottom (see figure 2 & 3 above and left). There are two kinds – hard corals which have rigid exoskeletons, or corallites, that protect their soft delicate bodies such as staghorn, brain, star, elkhorn and pillar corals and soft corals or gorgonians that lack an exoskeleton and sway with the currents, such as sea whips, sea fans, and sea rods.

The delicate balance of the coral reef relies entirely on the interaction of these hard and soft corals with sea life such as anemones, sponges, rays, lobsters, snails, crabs, turtles and dolphins (see figure 4 below). (Reef Relief, May 2009)

More subject matter in this paper:-
Mangroves and Sea Grasses…
Estuaries & Saltmarshes…
Fauna of the Coral Reefs…
Fauna of the Mangroves…
Fauna of the Estuaries…

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