Sea otter eating urchins (Enhydra lutris)

The kelp forest ecosystem is a very important and productive ecosystem. Many species of many different types are associated with and are partly or wholly dependent on it. The sea otter is recognized as a keystone species of the kelp forest ecosystem—it plays a vital role in the maintenance and health of this ecosystem. Of particular note is the sea otter’s role in keeping the sea urchin populations in check. Urchins are herbivores and will graze on kelp. If their numbers aren’t kept in check the magnitude of their grazing can be overwhelming and devastating to the kelp forest (notably, when they eat through the portion of the kelp stalks that anchor them to the sea floor this causes these kelp plants to be washed away by the current and surf). This photo shows a sea otter engaged in this vital role—she is in the process eating an urchin while a second one lies on her chest waiting to be eaten next.