How does the sea urchin and the sea otter maintain balance and keep the kelp ecosystem healthy

The role of the top predator is to maintain the balance between the population of secondary consumers, primary consumers and the producers. The removal of the sea otters, a top predator will lead to the increase in the number of the secondary consumers that include the creatures like the crabs, frogs, fishes, etc. These creatures are also eaten by the gulls and the eagles. This will lead to increase in the number of the gulls and the eagles as they have more food for themselves. The removal of sea otter decreases the competition over food with the gulls and the eagles. This is an indirect benefit to them.