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Global Governance of the Oceans

Ocean pollution and its management

  • 3 things to know
  • A2 Unit 3

Overview

Four sources of ocean pollution, how agricultural run-off reaches the sea and how eutrophication produces a dead zone.

What you need to know

Answer each one before you reveal it.

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Key term

Trace the route from a fertilised field to a stretch of sea in which nothing can live.

Key term

Name four sources of ocean pollution.

Key term

Explain how agricultural run-off reaches the sea.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Name four sources of ocean pollution.

    Model answer

    Terrestrial run-off from farmland and urban areas, sewage and waste disposal, oil spillage from ships and platforms, and plastic waste.

  2. 2

    Explain how agricultural run-off reaches the sea.

    Model answer

    Fertiliser not taken up by crops is washed off fields into streams and rivers, which carry the nutrients downstream and out into coastal waters.

  3. 3

    Define eutrophication.

    Model answer

    Eutrophication is the enrichment of water with nutrients, which triggers excessive algal growth.

  4. 4

    Describe how eutrophication produces a dead zone.

    Model answer

    Nutrients cause an algal bloom, the algae die and are decomposed by bacteria that consume the dissolved oxygen, and the water becomes too deoxygenated to support fish or shellfish.

  5. 5

    Name a well-known marine dead zone.

    Model answer

    The Gulf of Mexico dead zone, fed by nutrients carried down the Mississippi from the agricultural interior of the United States.

  6. 6

    Give two consequences of an oil spill on a coastline.

    Model answer

    Seabirds and mammals are killed when oil coats their feathers or fur, and the fishing and tourism industries lose their income for years.

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