Sea otters are important predators of sea urchins, an animal that eats giant brown kelp in continental shelf zones where they form huge kelp beds. it was observed that the removal of sea otters from the west coast led to an increase in the sea urchin population. these sea urchins fed on the large kelp fronds, destroying the kelp beds that serve as an important source of food and protection for spawning fish. what role does the sea otter play in this case? dominant species invasive species keystone species

In some case, I would say the sea otter would be both a dominant and keystone specie. Sea otters are main predators and most often are at the top or near the top of the food chain (whales and sharks would trump them easily as the top predators), but in this specific situation, the sea otter is a keystone species. A keystone species is an organism that more often than not an ecosystem can not continue without. In this situation, without the sea otter to control the sea urchin population is grew out of control and caused the expulsion of the giant brown kelp and havoc for the spawning fish. Thus, the sea otter is a must.