Marine Geography of India

Overview

India has a coastline of 11,098.81 km (revised April 2025 by the Survey of India; includes mainland + islands; previously cited as 7,516.6 km under older methodology) and an Exclusive Economic Zone (EEZ) of ~2.37 million km² — one of the world's largest. The surrounding waters — the Bay of Bengal, Arabian Sea, and Indian Ocean — are critical for India's climate, food security, trade (~77% of India's trade by volume is seaborne), and strategic interests.

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Maritime Zones (UNCLOS 1982)

India ratified UNCLOS (United Nations Convention on the Law of the Sea) in 1995. It defines maritime zones measured from the baseline (low water line along the coast):

1 nautical mile = 1.852 km

India's EEZ — Key Facts

Deep-Sea Mining (India's Claims)

• India has been allotted 75,000 km² of deep-sea mining area in the Central Indian Ocean Basin (CIOB) by the International Seabed Authority (ISA).
• Resources: Polymetallic nodules (manganese, nickel, cobalt, copper) on the seabed at ~5,000 m depth.
• India is a Pioneer Investor with ISA — one of the first nations to receive deep-sea mining rights.

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Ocean Currents around India

Arabian Sea Currents

Bay of Bengal Currents

• Bay of Bengal has a cyclonic (anti-clockwise) circulation in winter and anti-cyclonic (clockwise) in summer.
• East India Coastal Current (EICC): Flows northward in summer (SW Monsoon); southward in winter (NE Monsoon).

Indian Ocean Gyre

• The North Indian Ocean is unique: it is the only ocean where major surface currents reverse seasonally (driven by monsoon wind reversal).
• The South Indian Ocean has a permanent anti-clockwise gyre (Agulhas Current, South Equatorial Current, etc.).

Specific Currents to Know

Upwelling off India's Coast

• West coast (Malabar coast): Intense upwelling during SW Monsoon (May–September).
  • SW winds → offshore transport of surface water → cold, nutrient-rich deep water rises.
  • Makes Kerala–Karnataka coast highly productive fisheries zone (sardines, mackerel).
• Somali Upwelling: Strongest seasonal upwelling on Earth; cools Arabian Sea in summer.

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Coral Reefs

Distribution in India

Coral Reef Types

Coral Bleaching

• Coral bleaching occurs when seawater temperature rises by 1–2°C above normal for extended periods → coral expels symbiotic algae (zooxanthellae) → turns white → may die if stress prolonged.
• India has experienced bleaching events in: 1998 (mass bleaching linked to El Niño), 2010, 2016, 2020, 2024.
• 2024 mass bleaching: Worst on record globally; Indian reefs (Gulf of Mannar, Lakshadweep) significantly affected; linked to record Indian Ocean SSTs.

UPSC 2023: Questions on coral bleaching causes and conservation directly asked.

Coral Conservation

• Gulf of Mannar Marine National Park: Established 1986; India's first Marine NP in Tamil Nadu.
• Mahatma Gandhi Marine National Park: Wandoor, Andaman — protects fringing reefs.
• Lakshadweep Marine Protected Area: Under Environment Protection Act.
• Coral reef monitoring: National Centre for Coastal Research (NCCR), Chennai.

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Mangroves

India's Mangrove Status (ISFR 2023)

Major Mangrove Zones

Ecological Significance

1. Coastal protection: Mangroves absorb wave energy; proved critical during 2004 tsunami (villages behind mangroves had less damage).
2. Carbon sequestration: "Blue carbon" — mangroves sequester carbon 3–5× faster than tropical forests.
3. Fishery nursery: ~80% of commercially important fish species use mangroves as juvenile habitat.
4. Biodiversity hotspot: Sundarbans supports ~260 bird species, Bengal Tiger, Irrawaddy dolphin.

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Sea Level Rise and Coastal Vulnerability

Current Trends

• Global mean sea level rise: ~3.6 mm/year (2006–2015); accelerating to ~4.1 mm/year (IPCC AR6).
• Indian Ocean sea level rise: Slightly above global average — ~3.3–4.0 mm/year along Indian coasts.
• Subsidence (sinking land) + sea level rise = relative sea level rise — the effective threat.

Most Vulnerable Indian Coasts

Ghoramara Island (Sundarbans): One of India's most documented cases of island disappearance due to sea level rise + erosion — area shrunk by ~50% since 1970.

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Indian Ocean — Strategic and Economic Importance

Indian Ocean Trade Routes

• ~80% of global oil trade passes through the Indian Ocean.
• Critical chokepoints:
  • Strait of Malacca (between Malaysia and Indonesia) — busiest maritime lane; ~100,000 ships/year.
  • Strait of Hormuz (Persian Gulf exit) — 20% of global oil.
  • Bab-el-Mandeb (Red Sea entrance) — key for Suez Canal route.
  • Strait of Lombok (Indonesia) — alternate to Malacca for large tankers.
• India's geographic position at the apex of the Indian Ocean gives it strategic leverage over all these routes.

India's Blue Economy Policy (2021)

India's Blue Economy Framework identifies 7 thematic areas:

1. Marine fisheries
2. Aquaculture
3. Tourism and marine recreation
4. Offshore energy (wind, wave, tidal)
5. Seabed minerals
6. Marine biotechnology
7. Coastal infrastructure (ports, shipping)

SAGAR Initiative (Security and Growth for All in the Region): PM Modi's vision for the Indian Ocean region — India as the net security provider in the Indian Ocean.

Key Indian Ocean Organizations

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Marine Fisheries

India's Fisheries Overview

Major Marine Fishing Zones

• Kerala: Highest fish landing state; sardine and mackerel capital; Calicut/Kozhikode fishing harbour.
• Gujarat: Major marine catch; Veraval port — largest fishing port in India.
• Tamil Nadu: Second in marine catch; Rameswaram, Tuticorin.
• Andhra Pradesh: Major mechanised fleet.
• West Bengal: Hilsa (national fish of Bangladesh but also important for WB).

Key Species

• Hilsa: Most important commercially in Bay of Bengal (India, Bangladesh).
• Pomfret (Paplet): Premium fish; Arabian Sea.
• Indian Oil Sardine: Most landed species by volume.
• Shrimp/Prawn: Highest value export commodity.
• Tuna: Andaman & Nicobar waters.

Fisheries Issues

• Over-fishing: Many coastal fish stocks are fully exploited or over-exploited.
• Fishing ban season: India enforces a seasonal trawling ban (April 15 – June 15 in East coast; June 1 – July 31 in West coast) to allow fish breeding.
• PM Matsya Sampada Yojana (PMMSY): ₹20,050 cr scheme for fisheries development (launched 2020); targets 22 MMT fish production by 2024–25.

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UPSC Corner

High-Frequency Prelims Topics

• EEZ = 200 nautical miles from baseline; India's EEZ = ~2.37 million km².
• Territorial sea = 12 nm; Contiguous zone = 24 nm.
• 1 nautical mile = 1.852 km.
• Gulf of Mannar: India's first Marine National Park (1986); largest reef area on mainland.
• Lakshadweep: All islands are atolls (not fringing reefs).
• Sundarbans: World's largest mangrove delta; WB + Bangladesh; UNESCO WHS.
• Bhitarkanika: 2nd largest mangrove in India; Odisha; saltwater crocodile.
• Pichavaram: Tamil Nadu; mangrove between sea and Vellar estuary.
• West Bengal = India's largest mangrove state (~42.9%).
• Deep-sea nodules: India holds 75,000 km² in Central Indian Ocean Basin.
• SAGAR: Security and Growth for All in the Region — India's Indian Ocean vision.
• Veraval: India's largest fishing port (Gujarat).
• Coral bleaching: 1–2°C above normal SST → zooxanthellae expelled → whitening.
• Blue carbon: Mangroves, seagrasses, salt marshes — sequester carbon 3–5× faster than forests.

UPSC Mains GS1 Angles

1. "Examine the importance of India's Exclusive Economic Zone (EEZ) for resource security and strategic interests."
2. "Coral reefs of India are under increasing threat. Discuss the causes and consequences of coral bleaching."
3. "Mangroves are India's coastal shields. Assess the threats to mangrove ecosystems and measures to protect them."
4. "How do ocean currents around India influence its climate, especially the monsoon?"

GS3 / GS2 Angles

1. "India's Blue Economy potential remains largely unrealised. Critically examine the Blue Economy Policy 2021."
2. "India's fisheries sector faces the twin challenges of overfishing and climate change. Discuss the policy responses."
3. "UNCLOS governs India's maritime rights. How have recent disputes (South China Sea, Indian Ocean) tested this framework?"

MCQ Trap Awareness

• Trap: "India's EEZ is 200 km" → 200 nautical miles, not km (1 nm = 1.852 km → 370.4 km).
• Trap: "Lakshadweep has fringing reefs" → Lakshadweep islands are atolls.
• Trap: "Gulf of Mannar is in Kerala" → Tamil Nadu (between TN and Sri Lanka).
• Trap: "Bhitarkanika is in West Bengal" → Odisha.
• Trap: "Sundarbans is only in India" → Sundarbans spans India (WB) and Bangladesh.
• Trap: "Deep-sea mining is in the Bay of Bengal" → India's deep-sea area is the Central Indian Ocean Basin (CIOB).

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Key Facts at a Glance

• India's coastline: 11,098.81 km (revised April 2025; mainland + islands; Survey of India)
• EEZ: ~2.37 million km² (200 nautical miles)
• Territorial sea: 12 nautical miles
• 1 nautical mile: 1.852 km
• Deep-sea nodules area: 75,000 km² in Central Indian Ocean Basin
• Largest mangrove: Sundarbans (WB + Bangladesh); World's largest mangrove delta
• Largest mangrove state (India): West Bengal (~42.9%)
• Total mangrove cover: 4,992 km² (ISFR 2023)
• First Marine NP: Gulf of Mannar (1986)
• Best-developed coral reefs: Lakshadweep (atolls)
• Coral bleaching trigger: +1–2°C above normal SST
• Blue carbon: Mangroves sequester 3–5× faster than tropical forests
• India fish production rank: 2nd globally (~17.5 MMT; behind China) — detailed fisheries coverage in Ch38
• Largest fishing port: Kochi (Cochin) Fishing Harbour, Kerala — largest major fishing harbour; Veraval (Gujarat) = largest cluster of fishing vessels
• SAGAR: India's Indian Ocean vision — Security and Growth for All in the Region (2015; upgraded to MAHASAGAR, March 2025)