Acid rain ecological impact – UGC NET Question

Acid rain lowers the pH of freshwater bodies when acidic deposition exceeds their buffering capacity. As water becomes more acidic, many aquatic organisms experience physiological stress and reproductive failure. Sensitive species, especially certain fish and amphibians, may disappear, leading to reduced biodiversity and altered food webs. Hence, the major ecological impact is a drop in pH that causes the loss of sensitive species, as stated in option C.

Option A:
Option A is incorrect because acid rain does not simply increase hardness in a way that benefits fish. Instead, it acidifies the water, often dissolving toxic metals such as aluminium which further harms aquatic life.

Option B:
Option B is incorrect since acidification does not create an alkaline protective layer; it does the opposite by increasing hydrogen ion concentration. There is no protective film that neutralises acid automatically.

Option C:
Option C is correct as it summarises the chain of effects: pH reduction, physiological stress and eventual loss of species. This phenomenon has been documented in lakes affected by acid deposition, particularly in regions with low natural buffering.

Option D:
Option D is incorrect because acid rain adds pollutants rather than neutralises them. While some buffering may occur, lakes can become progressively more acidic if deposition continues.