Final answer:
A dead zone refers to an area in lakes and oceans near the mouths of rivers where large areas are periodically depleted of their normal flora and fauna. These zones can be caused by various human activities such as eutrophication, oil spills, and dumping toxic chemicals.
Step-by-step explanation:
A dead zone refers to an area in lakes and oceans near the mouths of rivers where large areas are periodically depleted of their normal flora and fauna. These zones can be caused by eutrophication, oil spills, dumping toxic chemicals, and other human activities.
One of the worst dead zones is off the coast of the United States in the Gulf of Mexico, where fertilizer runoff from the Mississippi River basin has created a dead zone of over 8,463 square miles. Phosphate and nitrate runoff from fertilizers also negatively affect several lake and bay ecosystems including the Chesapeake Bay in the eastern United States.