Thermal pollution is caused by?

• A. The addition of heat to water from power plants or industrial cooling water.
• B. Nutrient enrichment from agricultural runoff.
• C. Algal blooms due to excess phosphorus.
• D. Sediment suspension from erosion.

Answer: (A)

Thermal pollution happens when heat is added to a body of water by human activities, most commonly from power plants or industrial facilities releasing heated cooling water into rivers, lakes, or coastal areas. The key effect is raising the water temperature, which lowers the dissolved oxygen the water can hold and stresses aquatic life, often altering ecosystems and harming sensitive species.

The other scenarios involve chemical or physical changes rather than heat. Nutrient enrichment from agricultural runoff increases nitrogen and phosphorus in the water, fueling algal growth and eutrophication, not heat. Algal blooms caused by excess phosphorus are a result of nutrient input, not temperature rise. Sediment suspension from erosion raises turbidity and can smother habitats, but it’s about sediment load, not temperature increase.