Hot Topics : Coral Reefs and Coral Reef Watch (GS-1 & GS-3 Mains)

Coral Reefs and Coral Reef Watch


Question : Why is Coral Reef Watch considered crucial for coral reef conservation efforts?

Coral Reef Watch (CRW)

  • Established by National Oceanic and Atmospheric Administration (NOAA) in 2000.
  • Provides global analysis of sea surface temperature to identify coral reefs at risk of bleaching.
  • Free online tool with remote monitoring and actionable intelligence for coral reef resilience.

Importance of Coral Reefs

  • Most diverse ecosystems on Earth.
  • Provide economic and societal benefits worth $9.8 trillion annually.
  • Threatened by climate change, unsustainable fishing, and pollution.

Coral Reefs and Symbiotic Relationship

  • Reefs are built by coral polyps with calcium carbonate.
  • Zooxanthellae algae live inside corals, providing them with up to 90% of their energy through photosynthesis.
  • Corals provide habitat for various marine life.

Favorable Conditions for Coral Reefs

  • Temperature: 23°C to 25°C (not below 20°C or above 35°C)
  • Salinity: 27% to 40%
  • Depth: Shallow water, less than 50 meters (ideally)

Coral Bleaching

  • Corals expel zooxanthellae due to rising water temperatures, losing color and nutrients.
  • Severe bleaching leads to disease and death.
  • Measured in Degree Heating Weeks (DHW).

Coral Reef Watch Updates

  • Version 3.5 Thermal History product suite (1985-2023) released in January 2024.
  • Bleaching Alert Levels 1-5 introduced in December 2023:
    • Level 3: Risk of multi-species mortality.
    • Level 4: Risk of severe, multi-species mortality.
    • Level 5: Risk of near complete coral mortality (>80%).


  • Coral Reef Watch is crucial for coral reef conservation efforts.
  • Provides accurate information to scientists, policymakers, and communities for mitigating threats.


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