UPSC Prelims 2011 · GS Paper I

Question 47: Environment and Ecology

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 ?

1.Discharge of nutrients from the estuaries.
2.Run-off from the land during the monsoon.
3.Upwelling in the seas.

Select the correct answer from the codes given below :

a1 only

b1 and 2 only

c2 and 3 only

d1, 2 and 3

AnswerThe answer is (d).

Harmful algal blooms are triggered by nutrient enrichment of coastal waters. Nutrients reach the sea from estuaries, from land run-off in the monsoon that carries fertiliser, sewage and soil, and from upwelling that lifts nutrient-rich deep water to the surface. In warm, sunlit and calm waters the algae then multiply rapidly, and some species release toxins that kill fish. All three factors can therefore cause blooms.

1. Estuaries discharge nutrients into coastal water.
2. Monsoon run-off carries nutrients from land.
3. Upwelling brings nutrient-rich deep water to the surface.

How you could have got this

If you were sure statement 1 is correct, (c) goes: it leaves 1 out.
What you needed to know: Estuaries discharge nutrients into coastal water.
Then, if you were sure statement 3 is correct, (a) and (b) go: each of them leaves 3 out.
What you needed to know: Upwelling brings nutrient-rich deep water to the surface.

Only (d) is left. You didn’t need statement 2.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong

(a) Estuarine discharge is one cause, but not the only one.
(b) Omits upwelling, which also supplies nutrients to surface water.
(c) Omits estuarine discharge of nutrients.
(d) Right: estuaries, monsoon run-off and upwelling can all feed blooms.

Explanation: written by UPSC Grade, not by UPSC.

Practise this paper timedPrevious question Next question

Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.