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Friday, October 29, 2010

A question from ocean- What is coral bleaching?

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What is Coral Bleaching?

The whitening of coral colonies due to the loss of symbiotic zooxanthellae from the tissues of polyps is called as Coral Bleaching.

Zooxanthellae are unicellular algae that provide colour to corals. They provide food to corals and their deaths lead to breakdown of the symbiotic relationship between them. This breakdown of symbiotic relationship causes starvation and resultant deaths of coral polyps. This condition exposes the white calcium carbonate skeletons of the coral colony.





Image 1Coral (unbleached)


There are a number of stresses or environmental changes that may cause bleaching including disease, excess shade, increased levels of ultraviolet radiation, sedimentation, pollution, salinity changes, and increased temperatures.







Image 2 Coral (bleached)


Some Other causes of coral bleaching include -

·                     increased exposure to ultraviolet (UV) radiation;
·                     large amounts of storm water from heavy rains flooding the reef;
·                     the exposure of coral to certain chemicals or diseases;
·                     sediments such as sand or dirt covering the coral;
·                     Excess nutrients such as ammonia and nitrate from fertilizers and household products entering the reef ecosystem. (The nutrients might increase the number of zooxanthellae in the coral, but it is possible that the nutrient overload increases the susceptibility of coral to diseases.)


Steps of protection
- We should not pour gas, oil, dry cleaning fluid or other harmful chemicals into the sink, into canals or even onto the soil.
- We should recycle all batteries. When put into the trash, their toxic chemicals, such as mercury or cadmium, will leach into the soil and water; and water finally reaches to the sea.
-We should learn about coral reefs and educate others about their ecology.
- We should inform others by writing articles for the news paper, school news magazine or other publication.
-We should Support legislation that protects the reefs.
- We should Support laws that prohibit pollutants from reaching the reefs.
- We should reduce our carbon footprint by supporting carbon neutral programmes.
- We should not drop litter or dispose of unwanted items on beaches, or in the sea.
- Everyone must recognize and make specific decisions about the costs of waste disposal. Anyone may either accept the costs of waste treatment before it is discharged into waterways, or accept environmental impacts. Anyone can no longer simply assume that the sea is the cheapest and most effective place to dispose of sewage, urban, agricultural and industrial waste.