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Question

Difficulty: MediumCommand of Evidence: Textual

Marine biologist Dr. Elena Rostova and colleagues investigated the resilience of giant kelp (*Macrocystis pyrifera*) to marine heatwaves. Some researchers hypothesize that kelp forests situated near deep-water submarine canyons are more resilient to ocean warming than those along shallow continental shelves because these canyons facilitate the upwelling of cool, nutrient-rich subsurface water, shielding the kelp from warm surface temperatures. Rostova’s team monitored kelp canopy health at several canyon-adjacent and shelf-adjacent sites during a major heatwave.

Which finding from Rostova’s study, if true, would most directly support the researchers' hypothesis?

  1. A
    Kelp stands along the shallow continental shelves had higher rates of spore production before the heatwave than those near the submarine canyons did.
  2. B
    Both canyon-adjacent and shelf-adjacent kelp stands experienced similar rates of tissue decay and canopy loss throughout the duration of the heatwave.
  3. During the heatwave, canyon-adjacent kelp stands maintained stable growth rates and high nitrogen levels, whereas shelf-adjacent stands showed severe tissue degradation.Answer
  4. D
    Submarine canyons support a greater diversity of herbivorous species that consume giant kelp compared to shallow continental shelves.

Answer

The correct answer is the choice describing that canyon-adjacent kelp stands maintained stable growth rates and high nitrogen levels while shelf-adjacent stands degraded.
The correct answer is the option indicating that canyon-adjacent kelp stands maintained stable growth rates and high nitrogen levels, whereas shelf-adjacent stands showed severe tissue degradation. This finding directly supports the hypothesis because it shows a clear difference in health and resilience (stable growth versus tissue degradation) during the heatwave, and provides evidence of upwelling (high nitrogen levels, as nitrogen is a key nutrient carried by upwelled subsurface water).

Step-by-Step Solution

1
Identify the researchers' hypothesis in the passage.
The hypothesis is that giant kelp forests near submarine canyons are more resilient to marine heatwaves because the canyons facilitate the upwelling of cool, nutrient-rich water.
Understanding the specific hypothesis is necessary to determine what kind of evidence would support it.
2
Evaluate the choices to find one that demonstrates both higher resilience in canyon-adjacent kelp and a link to the proposed mechanism (upwelling of nutrients/cool water).
The choice describing stable growth rates (resilience) and high nitrogen levels (nutrient presence from upwelling) in canyon-adjacent kelp, compared to degradation in shelf-adjacent kelp, directly aligns with the hypothesis.
This finding provides direct textual evidence of both the outcome (resilience) and the underlying mechanism (nutrients).

Key Concept

Identifying textual evidence that supports a scientific hypothesis.
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Topics

Command of Evidence: Textual

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