Coral Reefs in India: Distribution, Types and Conservation

Coral Reefs in India: Distribution, Types and Conservation

Coral reefs are sometimes called the “rainforests of the sea.” They cover less than 1% of the ocean floor but support about 25% of all marine species. India has four major coral reef zones — each unique in type, ecology, and conservation challenge.

For UPSC, coral reefs appear in both Prelims (factual questions on distribution, bleaching) and Mains (GS Paper 3 on environment, conservation). This guide covers it all.

What Are Coral Reefs?

Corals are marine invertebrates belonging to the class Anthozoa (phylum Cnidaria). Each coral animal is called a polyp — a tiny, soft-bodied organism that secretes a hard calcium carbonate (limestone) skeleton. Over thousands of years, these skeletons accumulate to form coral reefs.

Coral-Algae Symbiosis

The key to coral survival is the relationship between corals and photosynthetic algae called zooxanthellae:

• Zooxanthellae live inside coral tissues
• They provide 90% of the coral’s energy through photosynthesis
• They give corals their characteristic colours
• This symbiosis only works in warm, shallow, clear, nutrient-poor water — which is why coral reefs exist in a narrow tropical band

Optimal conditions for coral growth:

• Temperature: 20–32°C (ideal: 25–29°C)
• Salinity: 32–40 ppt
• Depth: Mostly <50 m (sunlight requirement)
• pH: 8.0–8.3
• Clear, low-turbidity water

Types of Coral Reefs

Charles Darwin classified coral reefs into three types based on their relationship to land and sea level change. This classification remains standard.

1. Fringing Reefs

• Grow directly from the shoreline or very close to it
• No significant lagoon between reef and shore
• Most common type of reef globally
• Form in shallow water as coral grows outward from the coast
• India examples: Gulf of Mannar, Gulf of Kutch, parts of Andaman coast

2. Barrier Reefs

• Separated from the mainland or island by a lagoon
• Parallel to the coastline but offshore
• Much larger and older than fringing reefs (lagoon indicates subsidence)
• India: No classic barrier reef, but some reef structures near Andaman Islands have barrier-reef characteristics
• World famous: Great Barrier Reef (Australia) — world’s largest (~2,300 km)

3. Atolls

• Ring-shaped reefs (or horseshoe-shaped) enclosing a lagoon
• Form when a volcanic island subsides and the fringing reef continues to grow upward
• Found in deep water, far from continents
• India example: Lakshadweep Islands — classic atolls
• Also: Minicoy, Agatti, Kavaratti

Darwin’s theory of reef evolution: fringing reef → barrier reef → atoll (as volcanic island gradually subsides).

Western Ghats Biodiversity

Coral Reef Distribution in India

India’s coral reefs are distributed across four major zones:

1. Gulf of Mannar

• Location: Between Tamil Nadu coast and Sri Lanka; part of the Palk Strait region
• Type: Fringing reefs
• Area: ~117 km² of reef area across 21 islands
• Protection: Gulf of Mannar Marine National Park (1980) — India’s first marine national park; also a Biosphere Reserve
• Importance:

– High biodiversity: dugongs, sea turtles, dolphins, seahorses – About 3,600 species of plants and animals – 117 species of corals – Important seagrass beds

• Threats: Mechanized bottom trawling, coral mining for lime production (historically), sedimentation from Tamiraparani and Vaigai rivers, climate change

2. Gulf of Kutch

• Location: Between Gujarat coast and Kathiawar Peninsula
• Type: Fringing reefs (the northernmost reefs in India)
• Area: ~350 km² (though much is degraded)
• Protection: Gulf of Kutch Marine National Park and Sanctuary (largest in India by area for marine protected areas)
• Importance:

– Northernmost reefs in India and among the northernmost in the world – Adapted to extreme temperature variations (12°C in winter to 35°C in summer) – Home to puffer fish, sea snakes, rays, sharks – Green sea turtle nesting sites

• Threats: Industrial pollution (Jamnagar has a massive oil refinery complex, and the region has one of India’s most industrialized coastlines), tanker spills, coastal construction, temperature extremes

The Gulf of Kutch reefs are unusual for surviving in such extreme temperature and salinity conditions — they may hold insights into reef adaptation to climate change.

3. Andaman and Nicobar Islands

• Location: Bay of Bengal archipelago (~572 islands)
• Type: Fringing reefs along island shores, some patch reefs and near-atoll structures
• Area: ~1,000+ km² (estimated) — largest reef area in India
• Importance:

– Most diverse coral reef ecosystem in India – ~600 species of corals – Home to Dugong (sea cow), green and hawksbill sea turtles, whale sharks – Leatherback sea turtles nest in Great Nicobar – Outstanding fringing reefs around North Andaman, Neil Island, Havelock (Swaraj Dweep) – Coral gardens accessible to divers at Elephant Beach, Havelock

• Threats: 2004 Indian Ocean Tsunami caused massive damage to reefs around Andaman — some areas uplifted by 2 m, exposing reefs; others submerged. Crown-of-thorns starfish (Acanthaster planci) outbreaks, anchor damage from tourism, bleaching events

4. Lakshadweep Islands

• Location: Arabian Sea, 200–440 km west of Kerala
• Type: Atolls — classic examples of Darwin’s atoll theory
• Area: ~4,200 km² (lagoon + reef area); about 200 km² of actual reef
• Importance:

– Only atoll reefs in India – Over 100 coral species, 600+ fish species – Pristine reefs with high coral cover – Whale sharks and manta rays are regularly sighted – Migratory birds use the islands

• Threats: Mass bleaching (2016 bleaching killed significant portions of Lakshadweep reefs), sea level rise (low-lying atolls extremely vulnerable — average elevation <2 m), freshwater lens disruption, tourism pressure

National Parks of India

Coral Bleaching: Causes and Consequences

Coral bleaching is the most significant threat to coral reefs worldwide. It’s directly linked to climate change.

What Happens During Bleaching

When corals are stressed — usually by elevated sea temperatures (even 1°C above normal for 4+ weeks) — they expel the zooxanthellae algae from their tissues. Without the algae:

• Corals turn white (“bleached”)
• Corals are weakened but not immediately dead
• If temperatures return to normal within weeks, zooxanthellae can return and coral recovers
• If thermal stress persists, corals die

Causes of Coral Bleaching

Mass Bleaching Events in India

• 1998: First major mass bleaching event in India coinciding with the El Niño-Southern Oscillation; severe bleaching in Gulf of Mannar, Lakshadweep, Andaman
• 2010: Second major bleaching event; Gulf of Mannar reefs suffered significant mortality
• 2016: Worst bleaching event globally (coinciding with the 3rd Global Coral Bleaching Event, 2015–2017); Lakshadweep lost 60–70% coral cover; Andaman reefs severely affected
• 2020: Another bleaching event
• 2024: Fourth Global Coral Bleaching Event confirmed; Indian reefs were in high alert

Ocean Acidification

Beyond bleaching, ocean acidification poses an existential threat to coral reefs:

• The ocean absorbs about 30% of CO₂ emitted by human activities
• CO₂ + H₂O → H₂CO₃ (carbonic acid) → lowers ocean pH
• Ocean pH has dropped from ~8.2 to ~8.1 since pre-industrial times (seemingly small but represents a 30% increase in acidity due to logarithmic scale)
• Lower pH reduces availability of carbonate ions that corals need to build their skeletons
• Aragonite saturation — below a critical level, coral skeletons begin to dissolve

Threats to Coral Reefs: Summary

Conservation Measures for Coral Reefs in India

Legal and Policy Framework

• Wildlife (Protection) Act, 1972: Corals listed under Schedule I; harvesting prohibited
• Environment (Protection) Act, 1986: Coastal regulation powers
• Coastal Regulation Zone (CRZ) Notification: Restricts development within 500 m of coast (now modified to tiered distances)
• Marine Protected Areas (MPAs): Gulf of Mannar MNP, Gulf of Kutch MNP, Mahatma Gandhi Marine NP (Wandoor, Andaman)
• Convention on Biological Diversity (CBD): India is a signatory
• CITES: Trade in corals controlled

Active Conservation Programs

• Coral Reef Recovery Program — Gulf of Mannar Biosphere Reserve Trust runs coral rehabilitation and fishing community engagement
• Coral transplantation experiments — ZSI (Zoological Survey of India) has conducted coral transplantation in Gulf of Mannar
• Coral gardening — Small-scale coral cultivation on underwater frames, used in Lakshadweep and Andaman
• Restricted entry zones — No-take zones around most sensitive reef areas
• Satellite monitoring — ISRO and NCSCM (National Centre for Sustainable Coastal Management) use satellite imagery to track reef health and bleaching
• NIOT (National Institute of Ocean Technology) — monitors sea surface temperature in reef areas
• Global Coral Triangle Initiative — India participates in international coral conservation frameworks

Community-Based Conservation

In the Gulf of Mannar, traditional fishing communities called Meenavar have ancestral knowledge of reef ecology. Conservation efforts increasingly involve local communities as reef watchkeepers — giving them stake in healthy reefs since their livelihoods depend on it.

Coral Reefs and Climate Change Projections

Scientists project that if global temperatures rise 1.5°C above pre-industrial levels (the Paris Agreement target), coral reefs will decline by 70–90%. At 2°C, more than 99% of coral reefs could be destroyed.

India’s SSTs (Sea Surface Temperatures) around its coral zones have risen by approximately 0.5°C over the past 50 years. The frequency and intensity of bleaching events are increasing.

There is significant concern about Lakshadweep’s atolls — they sit barely 1–2 m above sea level. Sea level rise of even 30–50 cm would make them uninhabitable and submerge the reefs.

Frequently Asked Questions