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Naturalist: The decline of coral reefs has various causes. One contributing factor is predation on coral by organisms such as the crown-of-thorns sea star, whose preferred food source is coral polyps. Human fishing practices have decreased the sea star's predators, such as the harlequin shrimp. It is also possible that runoff containing nutrients for phytoplankton has resulted in larger phytoplankton blooms: the crown-of-thorns sea star gladly eats phytoplankton.
Indicate in the table which cause-and-effect sequence would most likely, according to the naturalist, result in coral reef decline. Make only two selections, one in each column.
An increase in phytoplankton
A decrease in phytoplankton
An increase in crown-of-thorns sea stars
A decrease in crown-of-thorns sea stars
An increase in harlequin shrimp
| Passage Statement | Analysis & Implications |
| "The decline of coral reefs has various causes" |
|
| "One contributing factor is predation on coral by organisms such as the crown-of-thorns sea star, whose preferred food source is coral polyps" |
|
| "Human fishing practices have decreased the sea star's predators, such as the harlequin shrimp" |
|
| "runoff containing nutrients for phytoplankton has resulted in larger phytoplankton blooms" |
|
| "the crown-of-thorns sea star gladly eats phytoplankton" |
|
Based on our fact analysis:
Let's evaluate each option for both Cause and Effect roles:
For the Cause column: We need what initiates the harmful sequence. "An increase in phytoplankton" works perfectly because:
For the Effect column: We need what results from the cause AND leads to coral decline. "An increase in crown-of-thorns sea stars" is ideal because:
The complete sequence: More phytoplankton → More crown-of-thorns sea stars → Coral reef decline ✓
This matches the naturalist's explanation perfectly without adding speculation.