Coral Reef and Coral Bleaching

Coral Bleaching

Context:

Record temperatures around the world made Corals susceptible to bleaching.

About Corals:

  • They are marine invertebrates and are called the “rainforests of the seas”.
  • Made up of genetically identical organisms called polyps.
  • The tissues of these polyps contain microscopic algae known as zooxanthellae.
  • Thousands of such polyps live together to form a colony, which grow when polyps multiply to make copies of themselves.
  • Mutualistic relationship between corals and algae –
    • Corals – Supply compounds for photosynthesis to the zooxanthellae.
    • Zooxanthellae – Supply the coral with organic products of photosynthesis which are utilized by the coral polyps for synthesis of their calcium carbonate skeletons.
    • Zooxanthellae are responsible for the unique and beautiful colors of corals.
  • Favourable Conditions –
    • Warm tropical oceans with minimum temperature of 20° C (30° N and 25° S latitudes)
    • Oceanic water free of sedimentation
    • Transparent parts of ocean bodies
    • Relatively low salinity ocean bodies
  • Types – Fringing reefs, Barrier reefs, Atolls
  • Distribution in India –
    • Gulf of Kutch
    • Inter tidal areas on the West Coast of India
    • Lakshadweep Islands (Atolls)
    • Gulf of Mannar
    • Palk Bay
    • Andaman & Nicobar Islands

What is Coral Bleaching?

When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae (zooxanthellae) living in their tissues, causing them to turn completely white.


Consider the following statements:

  1. Most of the world’s coral reefs are in tropical waters.
  2. More than one-third of the world’s coral reefs are located in the territories of Australia, Indonesia and Philippines.
  3. Coral reefs host far more number of animal phyla than those hosted by tropical rainforests.

Which of the statements given above is/are correct?

[UPSC Civil Services Exam – 2018 Prelims]

  • 1 and 2 only
  • 3 only
  • 1 and 3 only
  • 1, 2 and 3

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