Context

The Gulf of Mannar coral reefs in Tamil Nadu are showing signs of significant revival, thanks to over two decades of scientific restoration initiatives led by research institutions and government agencies.

About Coral Reefs

• Definition: Coral reefs are underwater ecosystems formed by calcium carbonate structures secreted by coral polyps.
• Often termed the “rainforests of the sea”, they:
  • Support around 25% of marine biodiversity.
  • Protect coastlines from storm surges and erosion.
  • Offer livelihoods through fisheries and eco-tourism.
• Gulf of Mannar Reefs:
  • Spread over 21 islands.
  • Rich in coral species like Acropora, Montipora, Porites, among others.

Causes of Coral Degradation

Anthropogenic (Human-Induced) Factors:

• Coral mining (prevalent in the 1960s–1990s).
• Overfishing, use of destructive fishing gear, and marine pollution.
• Coastal development leading to sedimentation and habitat destruction.

Climate Change Impacts:

• Rising sea surface temperatures leading to mass bleaching events (notably in 2010 and 2016).
• Ocean acidification, reducing coral resilience and growth capacity.

Coral Restoration Efforts in the Gulf of Mannar

Implemented by:

• Suganthi Devadason Marine Research Institute (SDMRI)
• Tamil Nadu Forest Department (since 2002)

Restoration Techniques:

1. Artificial Substrates:
   • Concrete frames, clay pots, cement slabs for coral attachment.
2. Artificial Reef Modules (ARMs):
   • Triangular ARMs (TARs) and Perforated Trapezoidal ARMs (PTARs) to enhance coral settlement.
3. Coral Transplantation:
   • 20 coral species transplanted.
   • Fast-growing species like Acropora showed the highest survival.

Scale of Restoration:

• 51,183 coral fragments transplanted.
• 5,550 artificial substrates deployed.
• ~40,000 sq. metres of degraded reef restored.

Positive Outcomes

• Survival Rate:
  55–79% average survival; some species showed up to 89% survival.
• Coral Recruitment:
  In TARs, coral recruits increased from 1.23 (2004) to 24.77 (2020).
• Fish Density:
  Increased from 14.5 (2006) to 310 (2020) per 250 m²—indicating improved reef health.

Challenges in Coral Reef Conservation

1. Repeated Bleaching Events:
   • Rising ocean temperatures trigger stress and expulsion of symbiotic algae, leading to coral mortality.
2. High Cost and Labour-Intensive Methods:
   • Restoration involves trained divers, resources, and long-term commitment.
3. Genetic Imbalance from Over-Reliance on Fast-Growing Corals:
   • Dominance of Acropora risks low genetic diversity and ecosystem vulnerability.
4. Persistent Anthropogenic Pressures:
   • Plastic pollution, unregulated tourism, and coastal projects hamper natural recovery.

Way Forward

1. Scale Up Restoration Nationwide:
   • Replicate the Gulf of Mannar model in other reefs like Lakshadweep, Andaman, and Gujarat’s Lakpat reefs.
2. Community Involvement:
   • Train and engage local fishing communities as reef guardians.
3. Use of Technology:
   • Employ AI, drones, and satellite-based tools for reef mapping, monitoring, and early warning of bleaching.
4. Promote Heat-Resistant Corals:
   • Explore assisted evolution and genetic enhancement to build coral resilience.
5. Strengthen Global Collaboration:
   • Leverage international frameworks like SDG-14 (Life Below Water) and the Paris Agreement for funding and knowledge sharing.

Conclusion

The revival of coral reefs in the Gulf of Mannar is a testament to the power of science, policy, and community collaboration. It serves as a model for climate adaptation, marine biodiversity conservation, and sustainable livelihoods. To protect India's vast reef ecosystems, long-term commitment, innovation, and inclusive governance are essential.

Source: The Hindu