Which term best describes a region of water with too little oxygen for most aquatic life to survive?

• A. Hypoxic water
• B. Anoxic water
• C. Turbidity
• D. Dead zone

Answer: (D)

Oxygen depletion in water controls which organisms can survive. When a region experiences oxygen levels so low that most aquatic life cannot endure, it’s described as a dead zone. This term best captures the ecological consequence—a large area where life is severely reduced or nearly absent due to lack of oxygen.

Hypoxic water refers to low oxygen, but some organisms can still live there; anoxic water means effectively no oxygen at all, describing the chemical state rather than the broader ecological impact. Turbidity describes how clear the water is and does not directly indicate oxygen levels or livability for aquatic life. Therefore, dead zone is the most appropriate description for a region where most aquatic life cannot survive because of severe oxygen shortage.