Which nutrients are primarily responsible for eutrophication in water bodies?

• A. Chlorides and sulfates
• B. Carbon Dioxide and methane
• C. Nitrates and phosphates
• D. Sodium and potassium

Answer: (C)

Eutrophication is driven by excess nutrients that fuel rapid growth of algae and aquatic plants. In many waters, nitrogen and phosphorus are the nutrients that limit growth, so when nitrates (nitrogen form) and phosphates (phosphorus form) enter the system in high amounts—often from fertilizers, wastewater, or detergents—they trigger large algal blooms. When these blooms die, microbes decompose the organic matter and use up a lot of dissolved oxygen, leading to hypoxic conditions that harm fish and other aquatic life. Other substances like chlorides and sulfates are mainly salts that affect water chemistry but don’t directly cause nutrient-driven blooms. Carbon dioxide can support photosynthesis but isn’t the specific driver of eutrophication in most natural waters, and methane isn’t a nutrient for algae. Sodium and potassium are essential ions but don’t by themselves spark eutrophication. So nitrates and phosphates are the nutrients primarily responsible.