Great Barrier Reef

Why in news?

• Members of the United Nations World Heritage Committee are being lobbied to pressure Australia to commit to more ambitious climate action as part of its plan to slow the decline of the Great Barrier Reef.
• Since 2015, global heating has fuelled three mass bleaching events that weakened and killed corals across the entire span of the reef.

Great Barrier Reef

• 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 Bleaching:

• 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.

Prelims Question:

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