When the walleye pollock population decreased, there were more zooplankton available for the moon jellies to eat. Since the jellies had more energy storage molecules, they were able to reproduce more. This lead to more births than deaths in the moon jelly population, which caused the jelly population to increase.
The jellies may have increased because of an increase in zooplankton or a decrease in sea turtles. Organisms need to release energy from energy storage molecules in order to reproduce. Organisms in consumer populations get energy storage molecules from eating organisms in resource populations.
