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Difficulty: EasyExplicit Detail Retrieval

In marine biogeochemistry, the precipitation of biogenic silica by microscopic diatoms is constrained by surface ocean silicic acid concentrations. During the Eocene-Oligocene transition, a global expansion of diatom populations enhanced organic carbon export to the deep ocean, accelerating global cooling. Researchers analyzing sediment cores from the Southern Ocean discovered that despite regional cooling, diatom frustule accumulation rates in this region remained remarkably stable because upwelling of deep ocean water continuously supplied nutrient-rich silicic acid, compensating for reduced surface runoff.

Based on the passage, which of the following statements are explicitly supported? Select all that apply.

  1. Diatom frustule accumulation rates in the Southern Ocean maintained stability despite regional temperature drops.Answer
  2. Silicic acid was delivered to Southern Ocean diatom populations via upwelling deep water.Answer
  3. C
    Regional cooling during the Eocene-Oligocene transition led directly to a widespread decline in global diatom populations.

Answer

The supported statements are that diatom frustule accumulation rates in the Southern Ocean maintained stability despite regional cooling, and that silicic acid was delivered to Southern Ocean diatom populations via upwelling deep water.
Both correct choices directly paraphrase facts stated in the passage: the text notes that diatom frustule accumulation rates remained stable despite regional cooling, and that upwelling deep water supplied the necessary silicic acid.

Step-by-Step Solution

1
Locate explicit passage details regarding Southern Ocean accumulation rates and temperature.
The text explicitly states that 'diatom frustule accumulation rates in this region remained remarkably stable' despite regional cooling.
Direct retrieval of explicit facts from the core paragraph.
2
Identify the stated mechanism supplying silicic acid to the Southern Ocean diatoms.
The passage confirms that 'upwelling of deep ocean water continuously supplied nutrient-rich silicic acid'.
Verifies explicit cause-and-effect relationship described in the passage.
3
Evaluate statements regarding global diatom population trends.
The passage states there was a 'global expansion of diatom populations', contradicting claims of a decline.
Eliminating options that misrepresent explicit facts.

Key Concept

Explicit Detail Retrieval
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Explicit Detail Retrieval

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