Eutrophication of lakes sign – UGC NET Question

Eutrophication occurs when excess nutrients, especially nitrates and phosphates, enter a water body. These nutrients stimulate dense growth of algae and aquatic plants, creating algal blooms. When the algae die and decompose, oxygen in the water is depleted, often leading to fish mortality. Thus, algal blooms followed by fish kills are characteristic signs of eutrophication.

Option A:
Option A is incorrect because eutrophication produces excessive algae, not their sudden disappearance. Clear water usually indicates low nutrient levels.

Option B:
Option B is correct as it clearly links nutrient enrichment, algal growth and oxygen depletion. This sequence is widely documented in polluted lakes and reservoirs.

Option C:
Option C is incorrect since crystal-clear water with low biological activity suggests oligotrophic conditions, not eutrophication. Such lakes are nutrient-poor, not nutrient-rich.

Option D:
Option D is incorrect; lakes do not rapidly become deserts due to eutrophication. They may become choked with plants and lose fish, but water remains present.