Final answer:
The decline in bay scallops in the Atlantic Ocean is due to an increase in the mesopredator cownose ray population, a result of overfishing top predators like sharks. The correct option is 2).
Step-by-step explanation:
The reductions in bay scallops in the Atlantic Ocean can be attributed to changes in predator-prey dynamics, particularly related to overfishing and its ecological consequences. A key factor in the decline of bay scallops is the increase in the mesopredator cownose ray population, which occurs when apex predators like sharks are heavily fished and their numbers decrease.
This effect is part of a larger phenomenon called trophic cascades, in which the removal of top predators leads to an increase in the populations of their prey. These mesopredators then exert greater pressure on their own prey species, such as scallops. Therefore, the correct option to answer the student's question is 2) an increase in the mesopredator cownose ray population.