UPSC CSE Prelims
Question 21
There is a concern over the increase in harmful algal blooms in the seawaters of India. What could be the causative factors for this phenomenon ?
- Discharge of nutrients from the estuaries.
- Run-off from the land during the monsoon.
- Upwelling in the seas.
Select the correct answer from the codes given below :
View correct answer and explanation
Correct answer: D
Correct Option: D
Explanation: Harmful algal blooms can be triggered by enrichment with land-derived nutrients and by natural upwelling that delivers nutrients to sunlit surface waters.
Statement / Item-wise Analysis:
1: Correct - Correct: rivers and estuaries transport nitrogen and phosphorus into coastal seas.
2: Correct - Correct: monsoon runoff washes fertilisers and organic nutrients to the coast.
3: Correct - Correct: upwelling can bring nutrient-rich deep water into illuminated surface layers.
Option-wise Analysis:
A: Incorrect - omits supported items 2, 3.
B: Incorrect - omits supported item 3.
C: Incorrect - omits supported item 1.
D: Correct - includes the supported statements and excludes the unsupported ones.