Correct Answer:
Option B —
ii only
Analysis of Statements
i. It is an anthropogenic process and does not occur naturally.
Incorrect: While human activities (anthropogenic) like agriculture and sewage disposal significantly speed up the process, eutrophication is also a natural process. This is called "natural aging" of a lake, where over centuries, a lake gradually accumulates nutrients and fills with organic matter, eventually turning into land. Humans simply accelerate this timeline from centuries to decades (known as Cultural Eutrophication).
ii. Nitrate and phosphate are the main contaminants for eutrophication.
Correct: These two nutrients act as fertilizers. When they enter a body of water in high concentrations—usually from agricultural runoff (fertilizers) or detergents—they trigger an overgrowth of algae.
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The Mechanism of Eutrophication
To understand why this is a problem, it helps to see the chain reaction:
Nutrient Loading: High levels of Nitrates and Phosphates enter the water.
Algal Bloom: Algae grow rapidly on the surface, blocking sunlight.
Oxygen Depletion: When the algae die, bacteria decompose them. This process uses up nearly all the Dissolved Oxygen (DO) in the water.
Dead Zones: Without oxygen, fish and other aquatic organisms suffocate and die.
Answer verified by Quintessence Classes faculty — Karan Nagar, Srinagar.
