Eutrophication from Fertilizer Runoff

Steps:

• Fertilizers contain nutrients like phosphates and nitrates that wash into the river during rain.
• These excess nutrients promote rapid algal growth in the water.
• Algal blooms die and decompose, consuming oxygen and causing eutrophication.
• Eutrophication disrupts aquatic ecosystems by lowering oxygen levels.

Why C is correct:

• Eutrophication is defined as nutrient enrichment, primarily from phosphates in fertilizers, leading to algal overgrowth and oxygen depletion.

Why the others are wrong:

• A: Eutrophication results from increased, not decreased, mineral salts like phosphates.
• B: Desalination removes salts but has no role in nutrient-driven eutrophication.
• D: Oxygen levels decrease due to bacterial decomposition of algae, not increase.

Final answer: C