What process is described by excess nutrients causing algae blooms, then bacteria decompose the algae and use up oxygen?

• A. Cloudiness caused by suspended particles
• B. Rapid growth of algae caused by too many nutrients in water
• C. Water with no dissolved oxygen
• D. Excess nutrients cause algae blooms, then bacteria decompose the algae and use up oxygen

Answer: (D)

Excess nutrients in water fuel algal blooms, and when those blooms die, bacteria decompose the algae and use up the dissolved oxygen. This sequence reduces oxygen levels in the water, harming aquatic life and creating conditions of hypoxia or dead zones. This is the classic eutrophication process: nutrient enrichment triggers rapid algal growth, then decomposition by bacteria consumes oxygen, producing low-oxygen conditions.

The other descriptions don’t capture the full chain: simply cloudiness describes turbidity, not nutrient-driven blooms and subsequent oxygen use; noting rapid algae growth due to nutrients describes the trigger but not the oxygen-depletion step; and stating water has no dissolved oxygen describes the outcome, not the cause-or-consequence sequence.