UPSC Prelims 2012 Q50: Environment & Ecology – Climate Change & Greenhouse Gases
The acidification of oceans is increasing. Why is this phenomenon a cause of concern?
1. The growth and survival of calcareous phytoplankton will be adversely affected.
2. The growth and survival of coral reefs will be adversely affected.
3. The survival of some animals that have phytoplanktonic larvae will be adversely affected.
4. The cloud seeding and formation of clouds will be adversely affected.
Which of the statements given above is/are correct?
- (a) 1, 2 and 3 only
- (b) 2 only
- (c) 1 and 3 only
- (d) 1, 2, 3 and 4
Answer: (a) 1, 2 and 3 only
Explanation
Ocean acidification
The oceans absorb carbon dioxide, which forms carbonic acid.
This lowers the pH and reduces the carbonate that sea life uses to build shells.
| Statement | Verdict | Reason |
|---|---|---|
| 1. The growth and survival of calcareous phytoplankton will be adversely affected | Correct | They need carbonate to build calcium carbonate plates |
| 2. The growth and survival of coral reefs will be adversely affected | Correct | Coral skeletons are made of calcium carbonate |
| 3. The survival of some animals that have phytoplanktonic larvae will be adversely affected | Correct | Larvae with thin shells are the most sensitive |
| 4. The cloud seeding and formation of clouds will be adversely affected | Incorrect (as per the accepted key) | Cloud formation is not taken as a direct concern of acidification |
Key facts:
| Fact | Detail |
|---|---|
| Average ocean pH | Fallen from about 8.2 to 8.1 since the industrial age |
| Worst hit | Corals, molluscs, sea urchins, some plankton |
Answer: (a) 1, 2 and 3 only.
Why each option is right or wrong
- (a) CORRECT. Calcareous phytoplankton, coral reefs and shelled larvae are all harmed.
- (b) Incorrect. Statements 1 and 3 are also true; plankton and larvae suffer too.
- (c) Incorrect. Coral reefs are among the first to suffer from acidification.
- (d) Incorrect. Statement 4 on cloud seeding is not accepted as a concern here.
Key point
Ocean acidification: carbon dioxide forms carbonic acid, pH falls (8.2 to 8.1), less carbonate for shells; harms corals, molluscs, calcareous plankton and larvae.
Remember
More carbon dioxide, lower pH, weaker shells and corals.
Common mistakes
- Thinking the sea is becoming acidic; it is becoming less alkaline.
- Counting the cloud statement because some plankton release sulphur gases.
- Confusing acidification with coral bleaching, which is caused by warm water.
Exam tip
Acidification attacks anything with a shell or skeleton of calcium carbonate. Check each statement against that.
Sources
- IPCC — Special Report on the Ocean and Cryosphere in a Changing Climate (ocean acidification)
- NOAA Ocean Acidification Program — What is ocean acidification?