Ans. Coral reefs are marine structures formed by colonies of tiny living animals called polyps, which remain permanently attached to the ocean floor. These polyps use tentacle-like arms to catch food and live in large groups known as colonies. There are two types of corals—hard corals, which build the reef’s skeleton over time, and soft corals. The hard corals are the primary architects of coral reef systems that serve as vibrant hubs of marine biodiversity, often referred to as the "rainforests of the sea."

Ecological Significance of Coral Reefs

Rich Biodiversity Hotspots:
Coral reefs support an incredible variety of marine life. For example, the Great Barrier Reef alone is home to:
- Over 400 coral species
- Around 1,500 species of fish
- Nearly 4,000 mollusc species
- Six of the world’s seven sea turtle species
  This makes them critical for maintaining marine biodiversity.
Support for Human Livelihoods:
Coral reefs provide ecosystem services worth an estimated $375 billion annually. Over 500 million people globally depend on reefs for:
- Food security
- Tourism income
- Livelihoods through fishing
Natural Coastal Barriers:
Coral reefs can absorb up to 97% of wave energy, offering natural protection against:
- Storm surges
- High waves
- Coastal erosion
  This helps prevent loss of life, damage to infrastructure, and displacement of communities.
Ecological Balance and Productivity:
Coral reefs are crucial for nutrient recycling, maintaining food webs, and supporting a diverse range of interdependent marine organisms.

Impact of Coral Bleaching on Marine Ecosystems

Coral bleaching occurs when corals are stressed due to factors like increased sea surface temperatures, pollution, or ocean acidification. Under stress, corals expel zooxanthellae—the symbiotic algae that provide them with food through photosynthesis. This causes the coral to turn white, a phenomenon known as bleaching.

Loss of Coral Health and Productivity:
Bleaching weakens corals, reducing their ability to reproduce and increasing their susceptibility to disease and death.
Threat to Marine Biodiversity:
- Nearly 25% of all marine species depend on coral reefs at some stage of their life cycle—for breeding, feeding, or shelter.
- The decline of coral reefs threatens fish populations and disrupts marine food chains.
Impact on Coastal Communities:
- Reduced reef protection increases vulnerability to storm surges and flooding.
- Loss of fish habitats leads to reduced fishery yields, affecting the food security and income of coastal populations.
Long-Term Ecosystem Collapse:
Repeated and severe bleaching events can cause irreversible reef degradation, leading to the collapse of entire marine ecosystems and associated services.

Conclusion

As per the International Coral Reef Initiative, around 84% of the world’s coral reef regions have been affected by mass bleaching events, largely due to abnormally high ocean temperatures driven by climate change. If global warming exceeds 1.5°C, the survival of coral reefs becomes highly uncertain.

To protect coral reefs, it is essential to:

Limit global warming in line with the Paris Agreement (net-zero emissions by 2050).
Promote sustainable marine practices, and
Enhance global and local reef conservation efforts through scientific monitoring and community participation.

Way Forward

Strengthening marine protected areas (MPAs)
Promoting coral restoration programs
Reducing carbon emissions and ocean pollution
Enhancing international cooperation for reef conservation

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