What term describes low dissolved oxygen levels that are harmful to aquatic life?

What term describes low dissolved oxygen levels that are harmful to aquatic life?

• A. Hypoxia
• B. Anoxia
• C. Hypoxemia
• D. Dystoxia

Answer: (A)

Hypoxia describes low dissolved oxygen in water that begins to stress or harm aquatic life. When dissolved oxygen levels are reduced, many fish and invertebrates struggle to breathe, growth slows, activity declines, and they may move to areas with more oxygen or die if conditions persist. In environmental science, DO is measured in mg/L or percent saturation, and levels that fall well below what organisms need (often around 2 mg/L or lower for sensitive species) are considered hypoxic conditions. Anoxia would be a complete lack of dissolved oxygen, which is an extreme situation not implied by the term in this context. Hypoxemia is a medical term referring to low oxygen in blood, not in water, and dystoxia is an uncommon term that isn’t the standard way to describe low oxygen in aquatic environments.

Hypoxia describes low dissolved oxygen in water that begins to stress or harm aquatic life. When dissolved oxygen levels are reduced, many fish and invertebrates struggle to breathe, growth slows, activity declines, and they may move to areas with more oxygen or die if conditions persist. In environmental science, DO is measured in mg/L or percent saturation, and levels that fall well below what organisms need (often around 2 mg/L or lower for sensitive species) are considered hypoxic conditions. Anoxia would be a complete lack of dissolved oxygen, which is an extreme situation not implied by the term in this context. Hypoxemia is a medical term referring to low oxygen in blood, not in water, and dystoxia is an uncommon term that isn’t the standard way to describe low oxygen in aquatic environments.