Question

tides can deposit large quantities of dead vegetation within a salt marsh, smothering healthy plants and leaving a salt panne—a depression devoid of plants that tends to trap standing water—in the marsh’s interior. ecologist kathryn beheshti and colleagues found that burrowing crabs living within these pannes improve drainage by loosening the soil, leading the pannes to shrink as marsh plants move back in. at salt marsh edges, however, crab - induced soil loosening can promote marsh loss by accelerating erosion, suggesting that the burrowing action of crabs ______
which choice most logically completes the text?
choose 1 answer:
a can be beneficial to marshes with small pannes but can be harmful to marshes with large pannes.
b may promote increases in marsh plants or decreases in marsh plants, depending on the crabs’ location.
c tends to be more heavily concentrated in areas of marsh interiors with standing water than at marsh edges.
d varies in intensity depending on the size of the panne relative to the size of the surrounding marsh.

Explanation:

1. Analyze Option A: The text doesn't mention the size of pannes (small or large) affecting the crabs' impact. It focuses on location (interior vs. edges), so A is incorrect.
2. Analyze Option B: In the marsh interior (panne area), crabs improve drainage, allowing plants to move back (increase in marsh plants). At marsh edges, crab - induced soil loosening accelerates erosion, promoting marsh loss (decrease in marsh plants). The impact depends on the crabs' location (interior or edge), so this option matches the text.
3. Analyze Option C: The text doesn't compare the concentration of crab burrowing between marsh interiors with standing water and marsh edges. It's about the impact of burrowing, not the concentration, so C is incorrect.
4. Analyze Option D: The text doesn't discuss the size of the panne relative to the surrounding marsh affecting the intensity of crab burrowing. It's about location - based impacts, so D is incorrect.

Answer:

B. may promote increases in marsh plants or decreases in marsh plants, depending on the crabs’ location.