Eutrophication is the enrichment of a water body with excess nutrients, mainly nitrogen and phosphorus, which causes algal blooms and then reduces dissolved oxygen as the algae decompose.
- Main Causes: Fertilizer runoff, sewage, detergents, and other nutrient-rich wastes.
- Effects: High Biological Oxygen Demand, low dissolved oxygen, loss of aquatic biodiversity, and sometimes toxic blooms.
Source: Down To Earth