A study found that a jellyfish-like predator called Mnemiopsis leidyi caused big changes in a marine food web. When these predators were around, the small animals they ate (copepods) decreased in number, leading to more algae in the water. This happened because the copepods were no longer eating the algae. The increase in algae was not due to more algae being made, but because the copepods weren't eating it. This shows that even in the ocean, when a top predator like Mnemiopsis leidyi is present, it can cause a chain reaction that affects the whole ecosystem.