Marine resources

1. Classification and geographical controls

Marine resources can be classified as living, non-living and ecosystem-service resources. Living resources include fish, crustaceans, molluscs, seaweeds and microorganisms. Non-living resources include petroleum, natural gas, dissolved salts, seabed minerals and renewable energy. Ecosystem services include coastal protection, carbon storage, nutrient cycling and recreation. Marine genetic resources also offer potential applications in pharmaceuticals, industrial enzymes and biotechnology.

Distribution depends strongly on bathymetry, sunlight, nutrient supply and geological history. The continental shelf is relatively shallow and receives river-borne nutrients and sediments. Sunlight supports photosynthesis, while mixing can replenish nutrients in surface waters. Many shelf seas consequently support valuable fisheries. Thick sedimentary sequences in suitable geological structures also favour the formation and accumulation of oil and natural gas.

Biological richness should not be equated with uniformly high ocean productivity. Much of the tropical and subtropical open ocean is nutrient-poor because stratification restricts vertical mixing. Productive waters occur especially where nutrients reach the sunlit zone through upwelling, seasonal overturning or river discharge. Resource assessment therefore requires attention to local oceanographic conditions rather than latitude alone.

• Renewable does not mean inexhaustible: fisheries and seaweed stocks can decline when extraction exceeds regeneration.
• Mineral deposits and fossil fuels are non-renewable on human timescales.
• Coastal ecosystems provide benefits that may be economically valuable even without extraction.

2. Fisheries, mariculture and biological resources

Phytoplankton form the base of most marine food webs. Their growth depends on light and nutrients such as nitrate, phosphate and, for diatoms, silicate. Zooplankton transfer this production to fish and larger animals. Coastal upwelling along Peru–Chile, California, northwestern Africa and southwestern Africa sustains important fisheries. Wind-driven offshore transport of surface water allows colder, nutrient-rich subsurface water to rise.

Traditional fishing grounds include the Grand Banks near Newfoundland, the North Sea and the waters around Japan. Broad shelves, mixing and nutrient supply help explain their productivity. Where currents meet, fronts can concentrate organisms, but the meeting of warm and cold currents is not by itself a sufficient explanation for rich fisheries. Fish abundance also depends on breeding conditions, habitat quality and fishing pressure.

India’s marine fisheries operate along both mainland coasts and island territories. Sardines, mackerel, tuna, anchovies, shrimps and other species support livelihoods, processing and trade. Capture fisheries harvest naturally occurring stocks, whereas mariculture cultivates organisms in marine or coastal environments. Examples include mussel and oyster culture, marine cage farming and seaweed cultivation. Shrimp aquaculture is frequently practised in brackish-water ponds and should not be confused with offshore fishing.

Management challenges include overfishing, juvenile catch, destructive gear, bycatch and habitat degradation. Seasonal closures, mesh-size regulation, stock assessment and protection of breeding grounds support conservation. The maximum sustainable yield concept links harvest to stock regeneration, but uncertainty and ecosystem interactions justify precautionary management. Pradhan Mantri Matsya Sampada Yojana, launched in 2020, addresses fisheries development, infrastructure, productivity and value chains.

3. Minerals, hydrocarbons and freshwater

Offshore petroleum and natural gas occur mainly in sedimentary basins along continental margins. Mumbai High in the Arabian Sea is a major Indian offshore oilfield; the Krishna–Godavari basin is important for offshore hydrocarbons on the eastern margin. Exploration and production require costly infrastructure and involve risks such as oil spills, methane leakage and disturbance of coastal and marine habitats.

Marine minerals occur in several distinct settings. Polymetallic nodules lie on deep-ocean abyssal plains and contain manganese and iron, with economically interesting quantities of nickel, copper and cobalt. Polymetallic sulphides form around hydrothermal systems, commonly near mid-ocean ridges and back-arc basins, and may contain copper, zinc, gold and silver. Cobalt-rich ferromanganese crusts develop on exposed hard surfaces, especially seamounts. These deposits must not be treated as interchangeable.

Coastal placer deposits are concentrations of heavy minerals produced by weathering, river transport and wave sorting. Indian beach sands contain minerals such as ilmenite, rutile, zircon and monazite; monazite is significant for its thorium and rare-earth content. Seawater also supplies common salt and compounds of magnesium and bromine. Desalination converts seawater into freshwater, commonly through reverse osmosis, but entails energy demand, costs and concentrated-brine disposal.

Gas hydrates are ice-like crystalline solids in which water molecules trap gas, predominantly methane. They occur under high-pressure, low-temperature conditions in marine sediments and also in permafrost regions. India has investigated hydrate occurrences in its offshore basins. Their presence does not establish commercial recoverability: extraction faces technological, economic and environmental challenges, including potential methane release and sediment instability.

4. Ocean energy and ecosystem services

Tidal energy uses predictable tidal movements. Barrage systems exploit the difference in water level across an enclosure, while tidal-stream turbines use moving currents. India’s Gulf of Khambhat and Gulf of Kachchh are often identified for tidal potential. Wave energy captures wind-generated surface-wave motion; its suitability depends on wave climate, device efficiency and survival under storm conditions.

Ocean thermal energy conversion uses the temperature difference between warm surface water and cold deep water, generally requiring a difference of about 20°C for practical operation. Tropical oceans offer favourable conditions, although pumping costs and engineering complexity constrain deployment. Offshore wind is ocean-based energy, but its immediate source is atmospheric motion rather than tides or seawater heat. India has prioritised offshore wind development off Gujarat and Tamil Nadu.

Mangroves, seagrass meadows and tidal marshes store blue carbon in biomass and sediments. They also provide nursery habitats, reduce coastal erosion and support livelihoods. Coral reefs sustain biodiversity, fisheries and tourism while attenuating wave energy. Their conservation is therefore resource management, not merely wildlife protection. Pollution, dredging, warming, coral bleaching and ocean acidification can reduce these services.

5. Maritime rights and sustainable utilisation

The United Nations Convention on the Law of the Sea, adopted in 1982 and in force since 1994, provides the principal legal framework. Territorial waters extend up to 12 nautical miles from the baseline. The contiguous zone may extend to 24 nautical miles, while the exclusive economic zone may extend to 200 nautical miles. Within the EEZ, the coastal state has sovereign rights over exploration, exploitation, conservation and management of natural resources, subject to other states’ lawful freedoms.

Continental-shelf rights concern the seabed and subsoil, not the overlying water column. A coastal state’s legal continental shelf can extend beyond 200 nautical miles where UNCLOS conditions are met. The seabed beyond national jurisdiction is called the Area; its mineral resources are the common heritage of humankind. The International Seabed Authority, headquartered in Kingston, Jamaica, organises and controls mineral-related activities there. An exploration contract does not itself authorise commercial mining.

India’s Deep Ocean Mission, approved in 2021 under the Ministry of Earth Sciences, includes deep-sea technology, mineral exploration, biodiversity studies and ocean-climate services. Samudrayaan envisages human exploration using the MATSYA 6000 submersible. Such research can improve knowledge, but deep-sea mining raises concerns about sediment plumes, noise, habitat loss and very slow ecosystem recovery.

A sustainable blue economy combines economic opportunity with ecosystem protection and equitable livelihoods. Priorities include marine spatial planning, ecosystem-based fisheries management, pollution control, disaster resilience and stronger monitoring of illegal, unreported and unregulated fishing. Scientific resource estimates, environmental assessment and consultation with coastal communities should precede large-scale extraction.

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