UPSC Prelims 2011 · Question 92 of 100

UPSC Prelims 2011 question on Marine Upwelling Productivity

In the context of ecosystem productivity, marine upwelling zones are important as they increase the marine productivity by bringing the

1. Decomposer microorganisms to the surface.

2. Nutrients to the surface.

3. Bottom-dwelling organisms to the surface.

Which of the statements given above is/are correct?

  1. 1 and 2
  2. 2 only
  3. 2 and 3
  4. 3 only
Show answer

Answer: B. 2 only

Verdict

Correct Answer: 2 only

Analysis

Marine upwelling is the upward movement of deep, cold and nutrient-rich ocean water to the surface. It increases marine productivity by supplying nutrients to phytoplankton.

Statement by statement

1. Decomposer microorganisms to the surface — Incorrect

Upwelling does not mainly increase productivity by bringing decomposer microorganisms to the surface.

The key factor is the nutrients released by decomposition in deeper waters.

2. Nutrients to the surface — Correct

Deep ocean water is rich in nutrients such as nitrates, phosphates and silicates.

When upwelling brings these nutrients to the sunlit surface zone, phytoplankton grow rapidly, increasing marine productivity.

3. Bottom-dwelling organisms to the surface — Incorrect

Upwelling brings water and dissolved nutrients upward, not large bottom-dwelling organisms.

Benthos and deep-sea organisms are not the main reason for increased productivity.

Extra UPSC info

* Upwelling zones are highly productive marine ecosystems.

* They support large fish populations because phytoplankton form the base of the food chain.

* Major upwelling regions include the Peru or Humboldt Current, California Current and Benguela Current.

* Upwelling is often driven by winds and the Coriolis effect.

* El Niño can weaken upwelling near Peru, reducing fish catch.

* Do not confuse nutrient movement with movement of organisms.

How to crack it

Marine upwelling increases productivity because it brings nutrient-rich deep water to the sunlit surface zone.

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