Recently an “unprecedented” mass bleaching event has been recorded at Ningaloo Reef off Australia’s west coast.

Key Concerns Raised

• Extensive Coral Damage: Bleaching has impacted many coral species across deep and shallow reef areas.
• Temperature Surges: Ocean waters in Western Australia have been up to 3°C warmer than average over recent months.

• Potential Long-Term Effects: While bleaching does not mean immediate coral death, prolonged stress can cause mass mortality.
• Global Coral Bleaching Events: Documented by National Oceanic and Atmospheric Administration (NOAA)  in 1998, 2010, 2014-2017, and 2023-2024 as the fourth global mass bleaching event.
  • Scientists warn this may be the worst bleaching event since 2011.

About Corals

• Coral Polyps: Corals consist of genetically identical polyps that form large reef structures.
• Zooxanthellae Algae: These unicellular algae live within coral tissues, providing nutrients through photosynthesis.
• Types of Corals:
• • Hard Corals (Stony Corals): Build reefs by extracting calcium carbonate from seawater.
  • Soft Corals: Do not form reefs but attach to existing coral structures.

Ecological Importance

• Support 25% of marine biodiversity, including fish, crustaceans, and mollusks.
• Act as natural coastal barriers, protecting shorelines from erosion and storm surges.
• Contribute to fishing and tourism industries, benefiting global economies.

About Coral Bleaching

• When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae (zooxanthellae) living in their tissues, causing them to turn completely white. 
  • This is called coral bleaching.
• Reversibility: If temperatures stabilize quickly, corals can recover by regaining zooxanthellae.

Reasons for Coral Bleaching

Climate-Related Factors

• Rising Sea Temperatures: Global warming has caused SSTs to rise by 1°C in the last century.
• Marine Heatwaves: Rapid temperature increases trigger bleaching (e.g., 2020 event in the Gulf of Mannar, India).
• El Niño Events: Cause localized warming, worsening bleaching conditions.

Other Contributing Factors

• Sedimentation: Coastal development and bottom trawling deposit sediments that block sunlight, hindering coral photosynthesis.
• Ocean Acidification: As carbon dioxide levels rise, oceans take in more of it, leading to increased acidity in the water.
  • This heightened acidity hampers corals’ ability to form the calcareous skeletons they rely on for survival
• Biological Invasions: Invasive species like crown-of-thorns starfish and algae outcompete bleached corals.
• Chemical Pollution: Exposure to oil, herbicides, and heavy metals can kill zooxanthellae.
• Pathogen Attacks: Some coral diseases strip coral tissues, leaving behind a bare skeleton.

Impact of Coral Bleaching

• Loss of Marine Biodiversity: Coral-dependent species face habitat destruction.
• Decline in Fisheries: Affected reefs reduce fish stocks, harming livelihoods.
• Increased Coastal Erosion: Dead reefs can no longer protect shorelines.
• Economic Losses: Coral tourism and fisheries face major revenue declines.

Global Efforts to Conserve Coral Reefs

• International Coral Reef Initiative (ICRI): A global partnership to protect reefs, with India as a member.
• World Coral Conservatory Project: Establishing coral banks in European aquariums to aid reef restoration.
• Biorock Technology: Uses electric currents to stimulate coral growth (e.g., Gulf of Kachchh, India).
• Super Corals: Breeding heat-resistant coral strains to withstand rising temperatures.

Indian Government Initiatives for Coral Conservation

• Coral Transplantation Projects:
• • Gulf of Mannar Biosphere Reserve: Uses artificial reef structures to restore damaged reefs.
  • Lakshadweep and Andaman & Nicobar Islands: Coral gardening projects underway.
• National Coastal Mission: Aims to protect marine ecosystems, including coral reefs.
• Regulations on Coastal Development: Stricter policies to prevent habitat destruction.
• Marine Protected Areas (MPAs): Several MPAs safeguard coral ecosystems from overfishing and pollution.

Conclusion

Urgent action is needed to address climate change and human-induced stressors to protect coral reefs. Strengthening global and national conservation efforts can help sustain marine biodiversity and coastal economies.

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