Context: According to the U.S. National Oceanic and Atmospheric Administration (NOAA), the world is recently on the verge of a fourth mass coral bleaching event, potentially leading to the death of vast stretches of tropical reefs, including portions of Australia's Great Barrier Reef.

Key Points

• Ocean Heat and Climate Alert:  Marine biologists are on high alert due to months of record-breaking ocean heat fueled by climate change and the El Nino climate pattern.
• Coral Bleaching Process: Coral bleaching occurs when corals expel colorful algae living in their tissues due to heat stress.
• Consequences of Coral Bleaching: Without algae, corals become pale, vulnerable to starvation, and disease, which can devastate the ocean ecosystem, fisheries, and tourism-based economies.
• Previous Global Bleaching Events: The last global mass coral bleaching event was from 2014 to 2017, resulting in significant coral loss, including nearly a third of the Great Barrier Reef.
• Monitoring Bleaching Through Data: Scientists utilize sea surface temperature data and satellite imagery to determine bleaching thresholds in reef pixels across ocean basins.

  Coral Reef

  • About: Coral reefs are some of the most diverse ecosystems in the world.
  • Structure: Coral reefs are massive structures made of limestone deposited by coral polyps.
  • Referred to as: Rainforests of the sea,”

  oCoral reefs support approximately 25 percent of all known marine species

  • Condition: he ideal depths for coral growth are 45 m to 55 m below sea surface.
  • Sunlight: Abundant sunlight available. 
  • Temperature: The temperature of the water should be around 20°C. 
  • Types of corel reef: Fringing Reefs, Barrier Reefs, Atolls
  • Coral reef in India: Andaman and Nicobar Islands, Gulf of Mannar, Gulf of Kutch, Palk Strait and the Lakshadweep islands
  • Coral Bleaching: When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae microscopic algae called zooxanthellae living in their tissues, causing them to turn completely white.