The acidification of oceans is increasing. Why is this phenomenon a cause of concern?The growth and

Q: What is UPSC Prelims?

UPSC Prelims is a competitive examination conducted in India. This question is from the 2012 UPSC Prelims Environment & Ecology paper.

Q: How can I prepare for UPSC Prelims Environment & Ecology?

To prepare for UPSC Prelims Environment & Ecology, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2012 question covers Coral Reefs, Sea Floor & Oceanography topic.

Q: What is the difficulty level of this question?

This UPSC Prelims 2012 Environment & Ecology question has a hard difficulty level and is marked as an important question.

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You can find more UPSC Prelims previous year questions on AspirantMitraa. Browse by subject, topic, year, and difficulty level to practice effectively.

Question

The acidification of oceans is increasing. Why is this phenomenon a cause of concern?The growth and survival of calcareous phytoplankton will be adversely affected.The growth and survival of coral reefs will be adversely affected.The survival of some animals that have phytoplanktonic larvae will be adversely affected.The cloud seeding and formation of clouds will be adversely affected.Which of the statements given above is/are correct?

Accepted Answer

Correct Answer: D — 1, 2, 3 and 4Solution:Ocean acidification occurs when CO₂ from the atmosphere dissolves in seawater, forming carbonic acid — lowering ocean pH (currently about 8.1, down from 8.2 pre-industrial). All four statements describe genuine consequences:Statement 1 — Calcareous phytoplankton adversely affected: Correct. Calcareous phytoplankton (like coccolithophores and foraminifera) build calcium carbonate shells. Ocean acidification reduces the availability of carbonate ions, making it harder for these organisms to build and maintain their shells — shells dissolve more easily in more acidic water. ✓Statement 2 — Coral reefs adversely affected: Correct. Corals build calcium carbonate skeletons — ocean acidification weakens and dissolves these structures. Combined with rising sea temperatures (coral bleaching), acidification poses an existential threat to coral reef ecosystems globally. India's coral reefs (Gulf of Mannar, Lakshadweep, Andaman) are already under severe stress. ✓Statement 3 — Animals with phytoplanktonic larvae adversely affected: Correct. Many marine animals — including oysters, sea urchins, starfish, and various fish species — have larvae that are phytoplanktonic (floating freely in the water column). Acidification directly harms these larvae (which may have calcium carbonate structures) and also harms the phytoplankton they depend on for food — cascading through the food chain. ✓Statement 4 — Cloud seeding and formation adversely affected: Correct. This is the most subtle connection. Phytoplankton (particularly dimethyl sulfide or DMS-producing species) release sulfur compounds that evaporate into the atmosphere and act as cloud condensation nuclei — seeding cloud formation. Ocean acidification disrupts phytoplankton communities, potentially reducing DMS production and affecting cloud formation patterns — with further climate feedback effects. ✓Key Concept: Ocean acidification has been called 'the other CO₂ problem.' The ocean has absorbed about 30% of anthropogenic CO₂ emissions — but this comes at the cost of acidification. The Southern Ocean and Arctic Ocean are acidifying fastest. At current emission trajectories, ocean pH could fall to 7.9 by 2100 — a 150% increase in acidity (pH is logarithmic). Economic impacts: global fisheries and aquaculture worth billions of dollars are threatened; coral reef tourism and fisheries support hundreds of millions of people. Monitoring efforts: ARGO floats, ocean observation networks, and IPCC reports track ocean acidification trends. The Paris Agreement's 1.5°C target would significantly limit but not eliminate ocean acidification by 2100.

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