Which term describes the nutrient over-enrichment of aquatic ecosystems?

• A. Acidification
• B. Eutrophication
• C. Alkalinification
• D. Nitrification

Answer: (B)

Eutrophication is nutrient over-enrichment of aquatic ecosystems. It occurs when excess nutrients, especially nitrogen and phosphorus from sources like fertilizers, sewage, and runoff, enter lakes, rivers, or coastal waters. This spill fuels rapid growth of algae and aquatic plants, often creating blooms that reduce light and disrupt typical habitats. When these organisms die, their decomposition uses up a lot of dissolved oxygen in the water, leading to hypoxic conditions that stress or kill fish and other aquatic life. Over time, the ecosystem can become dominated by a few species, with reduced biodiversity and altered food webs.

Acidification refers to the lowering of water pH due to increased acidity, not to nutrient levels. Alkalinification is the opposite, involving higher alkalinity. Nitrification is a specific microbial process that converts ammonium to nitrite and then nitrate; it’s part of nitrogen cycling and does not by itself describe the broader phenomenon of nutrient over-enrichment.