Wednesday 18 July 2012


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Coral reefs form living sea beds that support rich ecosystems.  They are of immense value to wildlife and people, but come under pressure from many threats - mostly initiated by man.

They grow in the warm seas of the world and consist mainly of the skeletal remains of coral polyps; tiny creatures that amass in countless numbers to form a very slow growing colony.

Coral reefs are extremely rich habitats.  It has been estimated that the worlds reefs may support as many as half a million types of animal in all, including a third of fish fish species.

Reefs are also very important to people.  They can yield up to 20 tonnes of fish per square metre per year.  They protect coasts from storms and erosion.  They can also provide considerable revenue from recreation (the Great Barrier reef in Australia earns many millions per year).

Coral reefs need clear, warm, shallow waters with a  narrow temperature range, little sedimentation and good water circulation.  Disruption of these conditions can damage the reef ecosystem. 
Given time reefs can often recover from damage, even from the severe effects of a hurricane.  But human interference, from mining to pollution, can sometimes be too intense and damaging for the slow growing reefs and their rich wildlife to survive. 

There have been many reports of coral reef bleaching, where reefs lose their glorious colours and turn a ghostly white.  In September 1987 divers at a reef off Puerto Rico found themselves in a yellow-brown cloud rather than the usual crystal clear water.  

They were experiencing the breakdown of the relationship between coral polyps and the algae that live inside them.  The algae are believed to promote the polyps growth and help them produce the limestone skeletons that build the reef.  The divers were swimming through a cloud of algae released into the water as this vital relationship broke down, leading to bleaching.

Researchers believe raised sea temperatures are the principal cause of the breakdown.  Although temperatures can rise and fall naturally, the frequency and severity of bleachings are thought to be due to the effect of global warming.

Unless global warming is bought under control coral reefs could continue to suffer.  The more frequent and severe the bleachings are, the more difficult it will be for the worlds coral reefs to survive them.

For related articles click onto:
Acid rain and its effect on wildlife
Can starfish grow back their arms?
Caring for the coral reefs
Causes of acid rain

Coral reefs and the greenhouse effect
Conserving fossil fuels
Energy saving light bulbs
Fossil Fuels
Fossil fuels: Alternative sources of energy

How many seas are there in the world?
Keystone species
Sea animals: Sea Anemones
Seahorse facts
Star Starfish
The seahorse
What is the greenhouse effect?
What is a sea anemone?
What is a starfish?
What is a sea sponge?
What is a loofah?
What is a sea cucumber?
What is a cuttlefish?
What is fracking?
What is global warming?
What is the greenhouse effect?
What is the Gulf Stream?

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