Coral reefs, formed by thousands of tiny coral animals known as polyps, are large limestone structures found in tropical climates across over 100 nations.

Despite covering less than 0.5% of the earth’s surface, coral reefs support approximately 25% of all marine species.
Acting as natural breakwaters, coral reefs absorb 97% of wave energy, thereby reducing coastal erosion and flooding. However, rising ocean temperatures due to climate change have led to increasing events of coral bleaching.

According to the National Oceanic and Atmospheric Administration (NOAA), corals bleach when stressed by changes in temperature, light, or nutrients, leading them to expel the algae living in their tissues, turning them white.


Causes of Coral Bleaching:

Various factors contribute to coral bleaching, including:

  • Change in ocean temperature: Elevated sea temperatures are the primary cause of coral bleaching.
  • Runoff and pollution: Contaminants from agricultural runoff and industrial pollution can stress coral ecosystems.
  • Storms: Severe weather can physically damage coral structures and affect their ability to recover.
  • Overexposure to sunlight: High solar irradiance can increase water temperatures and stress corals.
  • Extremely low tides: Exposure to air during exceptionally low tides can cause bleaching in shallow-water corals.

Examples from the Great Barrier Reef:

  • The Great Barrier Reef, covering an area of 344,400 sq km, represents about 10% of the world’s coral reef ecosystems.
  • The 2019 Outlook Report by the Australian government identified climate change as the greatest threat to the Reef, along with other threats such as coastal development, land-based runoff, and illegal fishing.

Examples in the Indian Context:

  • In India, coral reefs are found in regions such as the Gulf of Mannar, Lakshadweep, Andaman and Nicobar Islands, and the Gulf of Kutch.
  • The coral reefs in the Gulf of Mannar and Lakshadweep have experienced bleaching due to rising sea temperatures and pollution from coastal activities.
  • Initiatives like the Coral Reef Recovery Programme by the Ministry of Environment, Forest and Climate Change aim to monitor and restore these vital ecosystems.


Corals form a symbiotic relationship with microscopic algae called zooxanthellae, which are crucial for their survival.

Coral reefs, a product of millions of years of evolution, play a critical role in maintaining planetary resilience and biodiversity.
Preserving coral reefs is essential for sustaining marine biodiversity, supporting scientific discoveries, and ensuring the well-being of human societies.

Legacy Editor Changed status to publish June 13, 2024