Answer: Option A) The seals would decrease in number and the phytoplankton would increase in number
Explanation:
The food web can be illustrated as follows: Seal --> Krill --> Phytoplankton
Where phytoplankton is the producer of food, krill is the primary consumer while seal is the secondary consumer.
So, reducing the krill population would immediately cause food shortage for seals, and lessen consumption of phytoplanktons.
Thus, the seals would decrease in number due to starvation and death, while the phytoplankton would increase in number