Causes & Impacts of Oil Pollution (Cambridge (CIE) IGCSE Environmental Management): Revision Note

Causes of oil pollution

• Marine oil pollution occurs when crude oil or refined oil products are released into the ocean or onto coastlines

• Oil pollution has several human-related causes, linked to extraction, transport, processing and shipping operations

Off-shore and on-shore oil extraction

• Oil extraction refers to drilling to remove oil from beneath the land or sea floor

• Off-shore oil extraction rigs can leak oil during drilling or pumping, or due to equipment failure

  • Accidents such as blowouts release large quantities of oil into the sea

  • These spills harm marine species and can reach coastlines

• On-shore extraction can lead to oil run-off

  • Oil can enter rivers that eventually flow into the ocean

Pipelines

• Pipelines transport oil across land or under the sea

• Corrosion, damage or poor maintenance can cause leaks

• Leaked oil may flow into rivers or coastal waters

• This spreads pollution over long distances

• Undersea pipeline leaks are difficult to detect and repair

  • This means oil can escape unnoticed for long periods

Shipping

• During transport of oil in tankers, accidents, collisions or grounding of these ships can release large amounts of oil

• Operational spills occur during refuelling or transferring oil between ships

  • Even small spills accumulate in busy shipping lanes

• Heavy shipping traffic increases the risk of pollution events

Cleaning of tanks at sea

• Tankers periodically clean out oil residues from their storage tanks

• Waste oil and oily water may be illegally released into the ocean

• Oil residue discharge can cover large areas with thin films of oil

• This harms marine organisms such as fish eggs, plankton and seabirds

Refineries

• Oil refineries process crude oil into petrol, diesel and other products

• Wastewater and oily sludge from refineries can escape into rivers or coastal areas if not treated properly

• Accidental leaks from storage tanks contaminate nearby waters

• These pollutants can also reach marine ecosystems through drainage systems

Impacts of oil pollution

• Oil pollution harms organisms by

  • coating the bodies of organisms

  • blocking sunlight

  • reducing oxygen

  • introducing toxic chemicals

• Thick oil slicks and thin oil films both damage marine and coastal ecosystems

• Different groups of organisms are affected in different ways depending on how they breathe, feed or move

Birds

• Oil coats feathers, reducing waterproofing and insulation

  • This causes birds to lose body heat and they often later die from exposure

• Oiled feathers become heavy

  • Makes flying difficult and reduces ability to escape predators

• Eggs and nests may be contaminated, which can lead to lower hatching success

Marine mammals

• Oil covers the fur or skin of mammals such as seals or dolphins, reducing insulation and causing heat loss

• Oil can contaminate their food sources

  • This can cause poisoning when mammals consume tainted fish or invertebrates

Fish

• Oil reduces oxygen levels in water, causing fish to suffocate or suffer stress

• Gills may be damaged, making breathing more difficult

• Oil affects fish eggs and larvae

  • Causes deformities, poor development and lower survival rates

• Contaminated fish may carry toxins up the food chain

Crustaceans

• Crustaceans such as crabs, lobsters and shrimp absorb oil chemicals through their shells or gills

  • This affects growth, moulting and reproduction

• Oil settles into sediments where many crustaceans live

  • Burrowing species are exposed to long-term contamination

  • Like fish, their eggs and larvae are sensitive to toxins

Seaweeds

• Oil blocks sunlight, reducing photosynthesis

• As a result, seaweeds may die or grow more slowly

• Oil can coats surfaces where seaweed attaches

  • This makes it harder for young plants to anchor and grow

• Loss of seaweed reduces habitat for fish and invertebrates

  • This weakens coastal food webs

Coral reefs

• Oil coats coral surfaces

• Blocks sunlight needed by the coral’s symbiotic algae

• Coral polyps absorb toxic chemicals

  • This can contribute to coral bleaching, stress or death

• Damage to coral reduces biodiversity in the surrounding ecosystem

Beaches

• Oil washes up onto beaches and coats sand and rocks

• This harms organisms living in the sand, such as small crustaceans

• Thick layers of oil also stop people being able to use beaches for recreational purposes

  • Beaches may need expensive clean-up operations