What is eutrophication, and which nutrients typically drive it?

• A. Eutrophication is the depletion of nutrients; driven by calcium and magnesium.
• B. Eutrophication is nutrient-driven overgrowth of algae; mainly nitrates and phosphates promote it.
• C. Eutrophication is the process of water becoming more acidic; driven by carbon dioxide.
• D. Eutrophication is the chemical weathering of rocks; driven by silicates.

Answer: (B)

Eutrophication happens when a body of water gets overloaded with nutrients, especially nitrates and phosphates, which fuels rapid growth of algae and other aquatic plants. These nutrients typically enter water from fertilizer runoff, sewage, and detergents. When algal blooms become dense, they block light from deeper organisms and, as the algae die, decomposers use up a lot of the dissolved oxygen. That lowered oxygen can create dead zones where fish and other aquatic life struggle to survive. So nitrates and phosphates are the main drivers because they directly feed the excessive plant growth that starts the whole process. The other ideas aren’t correct because eutrophication isn’t about nutrient depletion, acidity from CO2, or the weathering of rocks; it’s about excess nutrients leading to overgrowth and oxygen depletion.