Great Barrier Reef has recorded its largest Coral Bleach

Source:  IT

Context: The Great Barrier Reef has recorded its largest annual coral cover decline in nearly 40 years, driven by severe coral bleaching, cyclones, and crown-of-thorns starfish outbreaks.

About Great Barrier Reef has recorded its largest Coral Bleach:

• What is Coral Bleaching?

• • A stress response in corals when symbiotic algae (zooxanthellae) are expelled from coral tissues.
  • Loss of algae removes the coral’s main food source and colour, leaving it pale or white.
  • Bleaching does not always kill coral, but prolonged stress can lead to mortality.

• Causes of Coral Bleaching:

• • Increased Sea Temperatures – Often from climate change and El Niño events.
  • Pollution & Runoff – Nutrient-rich runoff from agriculture promotes harmful algal blooms and reduces water quality.
  • Overexposure to Sunlight – High solar irradiance during heat events.
  • Extreme Low Tides – Exposes shallow corals to air and heat stress.
  • Cold Stress Events – Rare but possible, such as Florida Keys (2010).

• Process of Coral Bleaching:

• • Healthy State – Coral and algae (zooxanthellae) coexist in a symbiotic relationship, with algae providing most of the coral’s energy and colour through photosynthesis.
  • Stress Trigger – Environmental changes like warmer sea temperatures, pollution, or extreme sunlight disturb this balance, causing physiological stress to the coral.
  • Algae Expulsion – In response to stress, coral ejects the algae from its tissues, losing its primary food source and vibrant colour.
  • Bleached Stage – The coral’s transparent tissue exposes its white skeleton, leaving it weak, energy-deprived, and prone to disease.
  • Outcome – If stress is short-lived, algae return and the coral recovers; if prolonged, the coral dies and reef ecosystems degrade.

• Implications:

• • Ecosystem Collapse – Coral reefs host ~25% of marine species.
  • Economic Loss – Impacts fishing, coastal protection, and tourism.
  • Biodiversity Decline – Loss of breeding grounds for marine life.
  • Climate Feedback Loop – Dead reefs store less carbon and lose their role as natural wave barriers.