UPSC Prelims 2024 CSAT Paper II · Q52 of 79 Comprehension easy

Passage

Geographers analyzed 175 satellite images of ocean colour, which is an indicator of phytoplankton productivity at the ocean's surface, and found that giant icebergs are responsible for storing up to 20 percent of carbon in the Southern Ocean. The researchers discovered that melting water from giant icebergs which contains iron and other nutrients, supports hitherto unexpectedly high levels of phytoplankton growth.

Based on the above passage, the following assumptions have been made : 1. Giant icebergs have a bearing on primary productivity and food chains of the Southern Ocean. 2. Melting of giant icebergs can produce climate change effects and impact world fisheries. Which of the assumptions given above is/are valid?

  1. (a) 1 only
  2. (b) 2 only
  3. (c) Both 1 and 2 ✓ UPSC's answer
  4. (d) Neither 1 nor 2

Why the answer is (c)

• The passage states that giant icebergs store up to 20 percent of carbon in the Southern Ocean, directly linking them to primary productivity, which validates Assumption 1.

• It further explains that melting water from these icebergs contains iron and nutrients that support high levels of phytoplankton growth.

• Phytoplankton form the base of the marine food chain; therefore, the nutrients released by melting icebergs influence the entire food web, supporting the validity of Assumption 1.

• Since phytoplankton productivity is a key driver of global carbon cycles and marine ecosystems, changes in this process (driven by iceberg melting) can have broader climate change effects.

• The impact on phytoplankton growth directly affects the availability of food for higher trophic levels, including fish, thereby impacting world fisheries, which validates Assumption 2.

• Consequently, both assumptions are logically derived from the facts presented in the passage regarding the role of icebergs in nutrient cycling and productivity.

Why the other options are wrong

(a) 1 only
This option is incorrect because it ignores the valid inference that changes in phytoplankton productivity due to iceberg melting can impact global fisheries and climate.
(b) 2 only
This option is incorrect because it fails to recognize the direct link between iceberg-derived nutrients and the primary productivity of the Southern Ocean described in the passage.
(d) Neither 1 nor 2
This option is incorrect because both assumptions are supported by the passage's description of icebergs' role in carbon storage, nutrient release, and phytoplankton growth.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2024, held on 16 June 2024. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

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