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Day 4 – Q 4. Describe where most of the world’s coral reefs are located. Give examples of islands or island groups that have coral reefs. What dangers does climate change pose for reefs? Discuss.

4. Describe where most of the world’s coral reefs are located. Give examples of islands or island groups that have coral reefs. What dangers does climate change pose for reefs? Discuss.

4.वर्णन करें कि दुनिया के अधिकांश कोरल रीफ कहाँ स्थित हैं। द्वीप या द्वीप समूह जहाँ  कोरल रीफ हैं का  उदाहरण दें । कोरल रीफ के लिए जलवायु परिवर्तन क्या खतरे उत्पन्न करता है? चर्चा करेंI


  • Introduction- What are coral reefs? – in a line or two. Its importance.
  • Location of most of the coral reels across world- world map is must here (rough sketch will do).
  • Examples of islands that have coral reefs.
  • Effect of climate change on coral reefs.
  • Conclusion- Way forward to protect coral reefs.


Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals. Coral reefs are built by colonies of tiny animals found in marine water that contain few nutrients. They are rightly regarded as rainforest of the ocean.

Location of most of the world’s coral reefs:

Coral reefs are found in all three of the Earth’s oceans that have portions in the tropics – the Atlantic, Pacific and Indian.

The global distribution of coral reefs is largely determined by the ecological requirements of the reef-building corals themselves.

  • Reef-building corals require warm water. The limits tolerated for long periods are from about 17-34 degrees C.  annual temperature regimes mainly restricted to tropical seas.
  • The coral animals require sunlight found in clear, shallow ocean waters. Depth of water should not be more than 180 feet.
  • The water should be saltish and free from sediments. Corals therefore survive best in moving ocean water well away from the silty coasts or muddy of mouths of streams.

Thus, the coral reefs are mainly concentrated towards the western margins of the tropical oceans.

Islands where coral reefs are found includes Andaman and Nicobar island, Seychelles, Maldives, Papua New Guinea etc.

Effect of climate change on coral reefs:

  • Warmer water temperatures brought on by climate change- If water temperatures stay higher than usual for many weeks, the zooxanthellae leave the corals. Without zooxanthellae, corals gets bleached. Bleached corals are weak and less able to combat disease.
  • Ocean acidification- The ocean absorbs approximately one-third of the atmosphere’s excess carbon dioxide, resulting in a more acidic ocean. In order for a coral reef to grow, it must produce limestone (or calcium carbonate) at a rate that is faster than the reef is being eroded. Ocean acidification slows the rate at which coral reefs generate calcium carbonate, thus slowing the growth of coral skeletons.
  • Increased sedimentation and melting of glaciers resulting into sea level rise- causes increases in sedimentation that can lead to the smothering of coral.
  • Changes in storm patterns- leads to stronger and more frequent storms that can cause the destruction of coral reefs.
  • Changes in precipitation- increased runoff of freshwater, sediment, and land-based pollutants contribute to algal blooms and cause murky water conditions that reduce light.
  • Altered ocean currents- leads to changes in connectivity and temperature regimes that contribute to lack of food for corals and hampers dispersal of coral larvae.


Coral reefs are important as they contain the most diverse ecosystems on the planet. They protect coastlines from the damaging effects of wave action and tropical storms and provide habitats and shelter for many marine organisms. Given climate change is the greatest global threat to coral reef ecosystems, efforts should be taken to tackle GHG emissions, strict implementation of INDCs, check on anthropogenic activities like oil spillage etc.

Best answer: Mayu

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