Concept:Eutrophication is the process by which water bodies become overly enriched with nutrients, leading to excessive plant and algal growth.
Explanation:When nutrients such as nitrogen (
N) and phosphorus (
P) enter rivers, lakes, or ponds, they act as fertilizers for algae.
These nutrients come mainly from agricultural runoff, sewage discharge, and industrial waste.
The high nutrient level triggers a rapid increase in algae, forming dense blooms on the water surface.
These algal blooms block sunlight and, when the algae die, their decomposition consumes much of the dissolved oxygen in the water.
Low oxygen levels can kill fish and other aquatic organisms, disturbing the ecosystem.
Therefore, the essential feature of eutrophication is the excessive growth of algae resulting from nutrient enrichment, not the direct release of toxic chemicals or heavy metals.
Answer:B. The excessive growth of algae due to nutrient enrichment