Fourth Global Mass Coral Bleaching Event

GS-3 Mains : Environment 

Short Notes or Revision Notes 

Question : Examine the implications of the fourth global mass coral bleaching event caused by rising ocean temperatures .

In the News:

  • National Oceanic and Atmospheric Administration (NOAA) confirms the fourth global mass coral bleaching event due to rising ocean temperatures.

History of Mass Bleaching:

  • 1st Event (1998): 20% of global reef areas affected.
  • 2nd Event (2010): 35% of reefs affected.
  • 3rd Event (2014-2017): 56% of reefs affected.
  • 4th Event (Current): Nearly 54 countries witnessing bleaching (Florida, US, Saudi Arabia, Fiji).

Causes of Rising Temperatures & Bleaching:

  • Rising greenhouse gas (GHG) emissions (CO2, methane) trap heat in the atmosphere.
  • Oceans absorb nearly 90% of this extra heat.
  • El Niño weather pattern further increases ocean temperatures.
  • Consequences: Threat to marine life, food security, jobs, and coastal protection.

What are Corals and Coral Reefs?

  • Corals: Sessile animals living in colonies on the ocean floor.
  • Types: Hard coral (reef builders) and soft coral.
  • Optimal Conditions: Temperature (20°C-35°C), Salinity (27%-40%), Shallow water (<50m).
  • Examples: Great Barrier Reef (Australia), Gulf of Kutch, Gulf of Mannar (India).

Coral Bleaching:

  • Symbiotic Relationship: Corals house zooxanthellae (algae) for food and color.
  • Stress Response: Corals expel zooxanthellae and turn white when stressed by temperature changes.
  • Bleaching doesn’t guarantee death but reduces coral reproduction and increases disease vulnerability.
  • Global Mass Bleaching: Significant bleaching across Atlantic, Indian, and Pacific Oceans.

Importance of Coral Reefs:

  • Exist for nearly 450 million years.
  • Support a vast array of marine life.
  • Provide economic benefits worth $375 billion annually.
  • Over 500 million people rely on reefs for food, income, and coastal protection.
  • Absorb wave and storm energy, preventing loss of life and property damage.

Way Forward:

  • Paris Agreement Goal: Limit global warming to 1.5°C.
  • Achieve net-zero GHG emissions by 2050.
  • Invest in climate change mitigation and adaptation strategies (SDGs 8 & 12).
  • Research heat-resistant coral varieties.


Leave a Reply

Your email address will not be published. Required fields are marked *