Answer:
The jellyfish population may have increased because of an increase in phytoplankton. This leads to an increase in zooplankton; a decrease in walleye pollock, leading to an increase in zooplankton; or an increase in orcas, leading to a decrease in sea turtles. Sea turtles, being the main predator for keeping the jellyfish population in check.
Also, if there are more red algae, jellyfish polyps have less place to grow. Without it, the polyps can attach itself on every surface.
Step-by-step explanation: