What is a dead zone in the ocean?
Quick Answer
A dead zone is an area of ocean or lake with so little dissolved oxygen that most marine life cannot survive, usually caused by excess nutrients from agriculture.
The Full Story
When fertilisers and sewage wash into waterways, they fuel explosive algal blooms. When the algae die, bacteria decompose them, consuming dissolved oxygen in the process. If oxygen drops below about 2 milligrams per litre, the area becomes hypoxic, and fish, crabs and other animals either flee or die. The Gulf of Mexico’s dead zone, caused largely by nutrient runoff from the Mississippi River, covers roughly 15,000 to 20,000 square kilometres in some years. The Baltic Sea has one of the world’s largest permanent dead zones. Climate change worsens the problem because warmer water holds less oxygen.
Key Facts
YouTube Angle
Suggested video title for this topic:
"Where the ocean suffocates — how dead zones form"