Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Eutrophication leads to increase in biological oxygen demand of water and increase the fish population in bottom water.
Reason R: Increase in algal growth in surface water due to inorganic contamination is called eutrophication.
In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is NOT the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Eutrophication: Nutrients $\rightarrow$ Algal bloom $\rightarrow$ Decomposition $\rightarrow$ Oxygen depletion $\rightarrow$ Fish kill.
Major sources: Agricultural runoff, domestic sewage, industrial effluents.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Eutrophication is the process of nutrient enrichment in water bodies leading to excessive algal growth.

Step 2: Detailed Explanation:
Assertion A:
Eutrophication leads to increased Biological Oxygen Demand (BOD).
When algal blooms die, they are decomposed by microorganisms, consuming oxygen.
This leads to oxygen depletion in the water.
Oxygen depletion causes fish kill, not an increase in fish population.
The statement says "increase the fish population in bottom water", which is incorrect.
This statement is not correct.
Reason R:
Eutrophication is caused by excessive nutrients (nitrates and phosphates) from sources like fertilizers and sewage.
These nutrients promote rapid algal growth in surface water.
This statement is correct.

Step 3: Final Answer:
Thus, A is not correct but R is correct.
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