UPSC Prelims 2012 · Question 99 of 98
UPSC Prelims 2012 question on Phytoplankton Destruction Effects
- ExamUPSC CSE
- Year2012
- PaperGeneral Studies Paper I
- SubjectEnvironment and Ecology
- TopicEcology and Ecosystem
- DifficultyMedium
- TypeStatement
What would happen if phytoplankton of an ocean is completely destroyed for some reason?
1. The ocean as a carbon sink would be adversely affected.
2. The food chains in the ocean would be adversely affected.
3. The density of ocean water would drastically decrease.
Select the correct answer using the codes given below:
Show answer
Answer: A. 1 and 2 only
Verdict
Correct Answer: 1 and 2 only
Statements 1 and 2 are correct because phytoplankton support ocean carbon sequestration and marine food chains, while ocean water density is mainly controlled by temperature and salinity.
Analysis
Phytoplankton are microscopic photosynthetic organisms found in the sunlit upper layers of oceans.
They are the base of the marine food chain and play an important role in carbon absorption.
Statement by statement
1. The ocean as a carbon sink would be adversely affected — Correct
Phytoplankton absorb carbon dioxide during photosynthesis.
When they die, some of this carbon sinks to deeper ocean layers and gets stored through the biological pump.
If phytoplankton are destroyed, the ocean’s ability to absorb and store carbon would reduce.
2. The food chains in the ocean would be adversely affected — Correct
Phytoplankton are the primary producers in marine ecosystems.
They are eaten by zooplankton, which are then eaten by fish and other marine animals.
Their destruction would disturb the entire marine food web from the base.
3. The density of ocean water would drastically decrease — Incorrect
Ocean water density mainly depends on temperature and salinity.
Phytoplankton biomass is very small compared to the total mass of ocean water.
Their destruction would not drastically reduce ocean water density.
Extra UPSC info
* Phytoplankton are often called the “grass of the sea” because they form the base of marine food chains.
* They live mainly in the euphotic zone, where sunlight is available for photosynthesis.
* They contribute significantly to global oxygen production.
* The biological pump helps transfer carbon from the surface ocean to deeper ocean layers.
* Excessive phytoplankton growth can cause algal blooms, oxygen depletion and dead zones.
* Do not confuse ecological impact with physical properties; phytoplankton affect food chains and carbon cycling, not ocean density in a major way.
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