Prelims 2011 · archive
EasyIn the context of ecosystem productivity, marine upwelling zones are important as they increase 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?
Answer & explanation
Answer: (b) 2 only
In an upwelling zone, wind pushes surface water away and cold, deep water rises to replace it. That deep water is rich in nutrients, which feed phytoplankton at the surface. Plankton is the base of the marine food chain, so productivity rises. Only statement 2 is correct.
- ✗ 1. Upwelling is a movement of water, not a transfer of decomposers. Decomposers live throughout the water column and sediments. They are not the reason productivity rises.
- ✓ 2. Water that wells up from below is cold and nutrient-rich. It fertilises the sunlit surface layer, so phytoplankton grow and the fish that feed on them thrive.
- ✗ 3. Bottom-dwelling organisms are not what raises productivity. The gain comes from dissolved nutrients that support primary producers at the surface.
Remember · Upwelling brings cold, nutrient-rich deep water to the surface. This boosts phytoplankton and fisheries, as off Peru. El Niño suppresses upwelling and cuts plankton and fish.
📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 13 (practise this chapter)
Sources
- NOAA National Ocean Service – What is upwelling? ↗ “This graphic shows how displaced surface waters are replaced by cold, nutrient-rich water that “wells up” from below.”
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 13 “The mixing of warm and cold currents help to replenish the oxygen and favour the growth of planktons, the primary food for fish population.”
Question: UPSC Civil Services (Preliminary) 2011, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·