Maarg Manthan · Topic 13.12

Marine Pollution: Sources and Effects

Environment & Ecology › Air, Marine, Noise and Other Pollution · Topic 13.12

Marine pollution is the entry into the sea of substances or energy that harm marine life, human health, fisheries and amenities. About four-fifths of it comes from land-based activities: untreated sewage, industrial effluent, agricultural runoff with fertilisers and pesticides, solid waste and plastics carried by rivers and drains. Other sources are shipping (oil from operational discharges and accidents, garbage, ballast water, antifouling paints and exhaust), offshore oil and gas activity, dumping of dredged material and wastes at sea, seabed mining, fishing gear and atmospheric deposition of pollutants. Effects include eutrophication and dead zones, oil coating of seabirds and shores, poisoning of food chains by heavy metals and persistent organic pollutants, ingestion and entanglement from plastics, damage to coral reefs, mangroves and seagrass, spread of invasive species through ballast water, underwater noise and risks to seafood safety. The main global rules are the UN Convention on the Law of the Sea (1982), MARPOL 73/78, the London Convention and Protocol on dumping, and the Ballast Water Management Convention (in force 2017).

5 min read · UPSC Prelims · Environment & Ecology · Air, Marine, Noise and Other Pollution

At a Glance

Land-based share About 80 percent
Shipping rule MARPOL 73/78
Dumping rule London Convention
Invasive route Ballast water
Law of the sea UNCLOS 1982
Exam link UPSC Prelims, Environment & Ecology: Air, Marine, Noise and Other Pollution

Where Does It Fit?

This topic opens the marine part of the macro on pollution. It leads to dead zones and acidification, oil spills and plastic debris, and then the coastal regulation rules. Previous topic: National Air Quality Index and Comprehensive Environmental Pollution Index. Next topic: Dead Zones and Ocean Acidification.

What Are the Sources of Marine Pollution?

Source	Details
Land-based sources	Sewage, industrial effluent, farm runoff and litter through rivers and drains; about four-fifths of marine pollution
Shipping	Oil from tank washing and accidents, garbage, sewage, ballast water, noise and air emissions
Offshore oil and gas	Leaks, blowouts, produced water and drilling muds
Dumping at sea	Dredged material, sewage sludge and wastes dumped from vessels
Fishing and aquaculture	Lost nets and gear, feed and chemicals
Atmospheric deposition	Pollutants carried by air to the sea, such as mercury and nitrogen
Seabed mining and coastal works	Sediment plumes and habitat damage

What Are the Effects and the Rules?

Eutrophication: nutrients cause algal blooms and low oxygen
Oil pollution: coats birds, fish and shores, and toxic compounds persist
Toxic chemicals: heavy metals and persistent organic pollutants accumulate and biomagnify
Plastics: entangle and are swallowed by animals and break into microplastics
Habitat damage: harm to reefs, mangroves and seagrass
Invasive species: carried in ballast water and on hulls
Human health: contaminated seafood, shellfish poisoning and beach disease
Economic loss: fisheries, tourism and coastal property

What Else Should You Remember?

UNCLOS: 1982; Part XII requires states to protect and preserve the marine environment
MARPOL 73/78: International Convention for the Prevention of Pollution from Ships, with six annexes on oil, noxious liquids, packaged harmful substances, sewage, garbage and air pollution
MARPOL Annex I: oil
MARPOL Annex V: garbage
MARPOL Annex VI: air pollution including sulphur limits for fuel
IMO: International Maritime Organization, the UN body for shipping, based in London
IMO 2020: global cap of 0.5 percent sulphur in ship fuel from 2020
London Convention 1972 and Protocol 1996: controls dumping of wastes at sea
Ballast Water Management Convention: adopted 2004, in force September 2017, requires treatment of ballast water
OPRC Convention 1990: oil pollution preparedness, response and cooperation
Bunker Convention: liability for oil pollution from ship fuel
Global Programme of Action: UNEP programme on land-based sources, adopted in 1995
Regional seas: UNEP regional seas programmes such as the South Asian Seas Programme
India: a party to MARPOL and other conventions; Merchant Shipping Act, 1958 and Coast Guard handle pollution response
Indian Coast Guard: designated authority for oil spill response in India
National Oil Spill Disaster Contingency Plan: India’s plan, with Coast Guard as coordinator
Coastal pollution hot spots: Mumbai, Chennai, Kochi, Gulf of Kutch and Hooghly estuary
Marine litter: ranges from bottles to fishing nets
Underwater noise: ship traffic and surveys harm whales and dolphins
Antifouling paint: tributyltin was banned under a 2001 convention because it harmed shellfish
Persistent pollutants: DDT and PCBs found in sea animals even in remote places
Ocean economy: the blue economy needs clean seas
Link to previous: see National Air Quality Index and Comprehensive Environmental Pollution Index
Link to next: see Dead Zones and Ocean Acidification
Link to coast: see Coastal Regulation Zone (CRZ) Notification, 2011
Caution: percentages for sources come from UN estimates and differ by study
Exam hint: learn each convention with the pollution type it covers
Sewage outfalls: coastal cities discharge partly treated sewage through pipes and creeks into the sea
Port and harbour activity: dredging, bunkering and cargo handling release oil, chemicals and sediment
Heat and radioactivity: power plant cooling water adds heat, and nuclear facilities release small authorised amounts of radioactivity
Coral and mangrove loss: pollution and sediment reduce light and oxygen for reefs and mangrove roots
Plastic from rivers: a small group of large rivers carries much of the plastic that reaches the sea

Why Does It Matter for the Exam?

Largest source: Land-based
Ships: MARPOL
Dumping: London Convention
Current affairs link: Plastics treaty talks
Common errors: mixing MARPOL with the London Convention

As an analytical point, most marine pollution starts on land, so controlling rivers, cities and farms is more important than ship rules alone. Ocean health is a basin-to-sea problem that needs coastal and inland action together.

Why Is This Topic Important?

Origin Land
Ships MARPOL
Harm Food chain

What Came Next?

The next topic covers dead zones and ocean acidification. Next topic: Dead Zones and Ocean Acidification.

Key People and Terms

MARPOL Ship pollution convention
IMO International Maritime Organization
Ballast water Water carried for ship stability
UNCLOS Law of the sea convention
OPRC Oil pollution response convention
Marine litter Waste in the sea

Exam Corner

Points to Remember

About 80 percent is from land.
Ships: MARPOL.
Dumping: London Convention.
Ballast water treaty in force 2017.
IMO 2020 sulphur cap: 0.5 percent.

Do Not Confuse With

MARPOL and London Convention Ship discharges versus dumping of wastes
UNCLOS and MARPOL General law of sea versus ship pollution rules
Oil spill and chronic oil pollution Accidents versus routine discharges

Memory Hook

Land sends eighty, ships spill, ballast hides a guest, treaties guard the sea.

Mains Angle

Questions ask for sources and treaties. These points help.

Sources Land first
Effects Food chain
Law MARPOL

A Question You May Face

An original practice question, not a past paper question.

“Discuss the sources and effects of marine pollution and the international and Indian measures to control it.”

How to Answer

Sources Land, ships.
Effects Eutrophication.
Law MARPOL.
India Coast Guard.

GS Relevance

Prelims: sources, conventions. GS Paper 3: marine pollution and ocean governance.

Frequently Asked Questions

What are the main sources of marine pollution?

About four-fifths of marine pollution comes from land-based sources, including sewage, industrial and agricultural waste and litter carried by rivers and drains. Other sources are shipping, with oil, garbage and ballast water, offshore oil and gas activities, dumping of wastes, fishing gear, seabed mining and atmospheric deposition.

What is MARPOL?

MARPOL 73/78 is the International Convention for the Prevention of Pollution from Ships, adopted under the International Maritime Organization. Its annexes cover pollution by oil, noxious liquid substances, harmful packaged substances, sewage, garbage and air emissions from ships, including limits on sulphur in fuel. India is a party to it.

How does ballast water cause pollution?

Ships take in water to stay stable and release it at other ports, which transfers aquatic organisms, bacteria and pathogens across the world's seas. These can become invasive species that damage local ecosystems and fisheries. The Ballast Water Management Convention, in force since 2017, requires ships to treat ballast water before release.

What is the London Convention?

The London Convention of 1972, strengthened by the 1996 London Protocol, controls the dumping of wastes and other matter at sea. It prohibits dumping of the most harmful substances, such as radioactive waste and industrial waste, and restricts dumping of other materials like dredged spoil, which require permits.

How does marine pollution affect people?

Marine pollution harms fisheries and food safety, because toxins and microplastics accumulate in seafood, and it causes shellfish poisoning and beach-related illness. It damages tourism and coastal livelihoods, harms coral reefs and mangroves that protect shores, and can raise health care and clean-up costs.

PYQ Practice — Statement Analysis

1 About 80 percent of marine pollution is from land-based sources.

True

Rivers and drains carry it.

2 MARPOL deals with dumping from land.

False

It deals with pollution from ships.

3 The Ballast Water Convention entered into force in 2017.