The sea otter is most likely to be a keystone species in the food web provided. This is because sea otters primarily feed on sea urchins, which are herbivores that consume kelp. If sea otters were to decline in population, sea urchin populations would increase and lead to a decrease in kelp forests. As kelp forests are integral to the entire ecosystem, the presence of sea otters is crucial to maintaining the balance of the food web.
