Causes & Impacts of Oil Pollution (Cambridge International IGCSE Environmental Management)

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

Exam Hint When describing the impacts of oil pollution on nature, try to link the effect to the organism's biology. For example, seabirds rely on waterproof feathers, and fish rely on clean water for oxygen.