Q. 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? (UPSC Prelims 2012)
Answer: 1, 2 and 3 only
Notes: The correct answer is [A] 1, 2 and 3 only.While there are emerging scientific theories regarding the relationship between marine life and cloud-forming gases, for the purposes of the examination, the focus remains on the direct and well-documented biological impacts of acidification.Why Acidification is a Cause for Concern:

• Calcareous Phytoplankton (Statement 1 is Correct): Organisms like coccolithophores rely on carbonate ions to build their calcium carbonate ($CaCO_3$) shells. As $CO_2$ dissolves in the ocean, it reduces the availability of these ions, making it difficult for these microscopic plants to survive. This disrupts the base of the marine food web.
• Coral Reefs (Statement 2 is Correct): Corals are highly sensitive to pH changes. Acidification decreases the "calcification rate," meaning corals grow more slowly and their skeletal structures become weaker and more prone to erosion or accidental breakage.
• Phytoplanktonic Larvae (Statement 3 is Correct): The larval stages of many marine species (including shellfish and some fish) are extremely vulnerable to chemical changes. Acidification can cause developmental deformities, impaired sensory systems, and higher mortality rates during these critical early life stages.
• Cloud Seeding (Statement 4 is Excluded): While some studies suggest that a reduction in certain phytoplankton might lead to less Dimethyl Sulfide (DMS) — a gas that helps in cloud formation — this is considered a complex climatic feedback loop. In the context of this specific question, it is not categorized as a primary or direct "cause for concern" like the biological threats listed above.