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Coral bleaching along Great Barrier Reef

2020 APR 8

Preliminary   > Geography   >   Oceanography   >   Coral bleaching


  • The Great Barrier Reef, the world’s largest coral reef ecosystem located in Australia, recently experienced its third major bleaching event in five years.


  • The Great Barrier Reef is located in the Coral Sea, off the coast of Queensland, Australia.
  • It is composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kms distance. It can be seen from outer space and is the world's biggest single structure made by living organisms
  • It contains the world’s largest collection of coral reefs, with 400 types of coral, 1,500 species of fish and 4,000 types of mollusks.


  • Coral reefs originate from a symbiotic relationship between the coral polyps and algae that live in the polyps. Coral bleaching occurs when the coral polyps expel these algae.
  • They occur due to factors such as variations in water temperature, acidity & salinity, extreme low tides, sea level rise, excessive sedimentation, zoonotic diseases, cyanide fishing and pollution.
  • When coral bleach occurs, it is not dead. Corals can survive a bleaching event. But as they come under more stress, they are subject to mortality.


Q. Which of the following events can trigger coral bleaching:

1.High water temperature

2. Dredging of sea floor

3. Low tides

4. Sea level rise

5. Dust storms

Choose the correct statements from the codes given below:   

a. 1, 2 and 4 only

b. 2,3,4 and 5 only

c. 1 and 3 only

d. All of the above

Answer to Prelims question