NEWS – The US National Oceanic and Atmospheric Administration (NOAA) recently declared the start of the fourth global mass coral bleaching event due to unusually high ocean temperatures

CORALS

• Corals are sessile animals that attach themselves to the ocean floor.
• They use tentacle-like structures to catch food and live in colonies of polyps.
  • Polyps are individual coral animals that form genetically identical groups.
• Types of Corals:
  • Corals are classified as hard corals and soft corals.
    • Hard corals have stony skeletons made of limestone produced by coral polyps.
    • Soft corals lack stony skeletons and have a more flexible structure.
  • Role of Hard Corals:
    • Hard corals are the primary builders of coral reefs.
    • Their stony skeletons form the basis of complex three-dimensional reef structures.
      • When polyps die, their skeletons remain and provide a foundation for new growth.
    • Coral Reefs:
      • Coral reefs are diverse ecosystems that have existed for around 450 million years.
      • They are often called “rainforests of the sea” due to their biodiversity.
        • Australia’s Great Barrier Reef is the largest coral reef system, spanning 2,028 kilometers.
      • Importance of Coral Reefs:
        • Coral reefs support a wide range of marine life and provide habitats for fish, plants, and other organisms.
        • They are crucial for coastal protection, tourism, and fisheries.

SIGNIFICANCE OF CORALS AND CORAL REEFS

• Biodiversity Hotspots:
  • Coral reefs are home to thousands of marine species, contributing to high biodiversity.
    • The Great Barrier Reef alone hosts over 400 coral species, 1,500 fish species, 4,000 mollusc species, and multiple sea turtle species.
  • Economic Value:
    • Coral reefs provide economic benefits estimated at around $375 billion annually.
    • They support industries such as fisheries, tourism, and pharmaceuticals.
      • Over 500 million people worldwide rely on coral reefs for food, income, and coastal protection.
    • Coastal Protection:
      • Coral reefs act as natural barriers that absorb up to 97% of wave energy during storms and floods.
      • This protection prevents loss of life, property damage, and soil erosion along coastlines.
    • Ecosystem Services:
      • Coral reefs contribute essential ecosystem services like carbon cycling and nutrient recycling.
      • They play a role in maintaining water quality and supporting fisheries productivity

CORAL BLEACHING

• Symbiotic Relationship:
  • Corals host algae called zooxanthellae in their tissues.
  • Zooxanthellae perform photosynthesis, providing corals with oxygen and nutrients while giving them vibrant colors.
• Sensitivity to Environmental Changes:
  • Corals are highly sensitive to changes in light and temperature.
  • Even slight environmental changes can stress corals.
• Coral Bleaching Process:
  • When corals are stressed, they expel zooxanthellae, leading to a loss of their colorful appearance.
  • This expulsion of algae results in corals turning completely white, hence the term “coral bleaching.”
• Impact on Coral Health:
  • Coral bleaching doesn’t immediately kill corals but increases their vulnerability to mortality and diseases.
  • Bleaching reduces coral reproduction rates and overall resilience.
• Global Mass Bleaching Events:
  • Global mass bleaching occurs when significant coral bleaching is observed across oceans.
  • The first recorded event was in 1998, affecting 20% of the world’s coral reefs due to heat stress.
  • Subsequent events occurred in 2010 (35% affected) and between 2014 and 2017 (56% affected), reflecting an increasing trend in coral bleaching incidents.
• Long-Term Consequences:
  • Continued coral bleaching events threaten the survival of coral reefs and the diverse ecosystems they support.
  • Severe and repeated bleaching can lead to widespread coral mortality and ecosystem degradation.

CURRENT GLOBAL BLEACHING EVENT:

• Confirmation and Scope:
  • NOAA has confirmed the fourth global bleaching event, affecting nearly 54 countries, territories, and local economies.
  • Affected regions range from Florida in the US to Fiji, with widespread bleaching reports.
• Severity at the Great Barrier Reef:
  • The Great Barrier Reef is experiencing its most severe bleaching event.
  • Approximately one-third of surveyed reefs show very high or extreme bleaching levels, and about three-quarters show some level of bleaching.
• Regional Confirmed Bleaching:
  • On April 15, bleaching was confirmed in the Western Indian Ocean, including areas like Tanzania, Kenya, Mauritius, Seychelles, and Indonesia’s western coast.
• Extent of Heat Stress:
  • Over 54% of the world’s coral area has experienced bleaching-level heat stress in the past year.
  • Heat stress levels are increasing by about 1% per week, indicating a growing impact on coral reefs.
• Key Driver:
  • Higher ocean temperatures are the primary driver of the bleaching event.
  • The situation has been worsened by the El Niño weather pattern, known for warmer oceans.
• Future Outlook:
  • While the current event is significant, there’s a potential for relief as El Niño weakens.
  • A cooler La Niña pattern may set in by year-end, potentially reducing the duration and severity of the bleaching event.

POTENTIAL IMPACTS OF THE ONGOING BLEACHING EVENT

• Severe Impact on Coral Reefs:
  • The current bleaching event is the most severe recorded, according to scientists.
  • Continued bleaching may lead to widespread coral mortality and ecosystem degradation.
• Depression and Concern Among Scientists:
  • Scientists like Ove Hoegh-Guldberg express concern and sadness over the severity of the event.
  • The situation is likened to a disaster movie, reflecting the gravity of the impact on coral reefs.
• Future Projections:
  • With rising global temperatures, such bleaching events are expected to occur more frequently and last longer.
  • Projections suggest that coral reefs could face significant loss even with a 1.5-degree Celsius increase in global temperatures.
• IPCC Report Findings:
  • The IPCC report highlights that coral reefs may face extensive damage with a 1.5 to 2-degree Celsius warming.
  • The Earth has already warmed by 1.1 degrees Celsius since 1850, indicating significant warming trends.
• Climate Action Requirements:
  • To limit global warming to 1.5 degrees Celsius, countries must achieve net zero greenhouse gas (GHG) emissions by 2050 as per the Paris Agreement.
  • However, current GHG emissions remain high, making it challenging to meet climate targets.
• Challenges and Outlook:
  • Achieving climate targets is crucial to mitigating the impact on coral reefs and marine ecosystems.
  • The ongoing bleaching event underscores the urgency of global climate action to protect coral reefs and biodiversity.