Earth Science

Human Impacts on the Earth Environment

Coastal Pollution

Study Tip
Dead zones can span hundreds or even thousands of kilometers of ocean at a time.

Ocean Pollution

  • Most ocean pollution comes originates from agricultural, industrial, and municipal waste and runs off into the oceans
  • 20% of water pollution enters the ocean directly from oil spills and waste that is directly dumped into the ocean
Study Tip
Dead zones can span hundreds or even thousands of kilometers of ocean at a time.

Effects of Coastal Pollution

  • Creates unsafe environments for both humans and wildlife
  • Rainfall can spread pollutants and the diseases associated with them
  • Pollution kills off a large proportion of fish that people rely on as a source of food

Dead Zones

A dead zone is a large area of ocean without fish or plant life. Many dead zones are near coasts since rivers carry fertilizer runoff.

How it happens:

  • Fertilizers run off of lawns and farm fields
  • Fertilizer promotes algae growth in the water that the fertilizer is in contact with
  • Lakes, rivers, and bays become clogged with algae and aquatic plants
  • These organisms eventually die and decompose
  • Decomposition uses up dissolved oxygen in water
  • Large numbers of plants and marine animals cannot thrive without oxygen  
  • A dead zone develops
Dead Zones
Dead zones off the coasts are indicated by
red dots on this diagram.
Concept Check
  • How is coastal pollution related to dead zones and ocean pollution?
  • How are dead zones created?