UGC NET Questions (Paper – 1)

Eutrophication occurs when excess nutrients, particularly nitrates and phosphates, enter water bodies from sewage or fertilisers. These nutrients stimulate rapid growth of algae and aquatic plants. When the biomass dies and decomposes, bacteria consume large amounts of oxygen, leading to hypoxic conditions that can kill fish and other organisms. Thus, algal blooms followed by oxygen decline and fish kills are characteristic.

Option A:
Option A is incorrect because eutrophication initially increases, not eliminates, algal growth.

Option B:
Option B is correct as it captures the sequence of nutrient enrichment, algal proliferation and oxygen depletion.

Option C:
Option C is incorrect; lakes do not suddenly become deserts, though they can become choked with vegetation and lose biodiversity.

Option D:
Option D is incorrect because crystal-clear water usually indicates low nutrient levels (oligotrophic conditions), the opposite of eutrophication.