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Practice problem

Pollution — Types & Examples

By Deena Hauze
1. During the spring, sun-heated freshwater runoff from the Mississippi River creates a barrier layer in the Gulf, cutting off the saltier water below from contact with oxygen in the air. 2. Nitrogen and phosphorus from fertilizer and sewage in the freshwater layer ignite huge algae blooms, When the algae die, they sink into the saltier water below and decompose, using up oxygen in the deeper water. 3. Starved of oxygen and cut off from resupply, the deeper water becomes a dead zone. Fish avoid the area or die in massive numbers. Tiny organisms that form the vital base of the Gulf food chain also die. Winter brings relief, but spring runoffs start the cycle anew.

Image source: By Dan Swenson | Staff Research CC BY SA-2.0, via flikr.com

Read the infographic above and then answer the following question. Which of the following is most likely an impact on the environment caused by dead zones?

Choose one answer

Type a concept, like “slope” or “photosynthesis”.

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