Keystone species hold together communities by helping to structure and maintain their habitat. The concept behind a keystone species is that they support species diversity through their presence, activities and abundance within the community (Mills et.al. 1993). If a disturbance happens within the community and the keystone species disappears, the organization and diversity drastically shifts. To be defined as a keystone species, there are few characteristics a species must have. The first is that their presence within the community must help structure and assist the diversity of their community (Mills et.al. 1993). The second is that they must have some importance to their community in relation to the other species who live there (Mills et.al 1993). The keystone species are at the top of the community structure, with few, if any, predators. They control the population density of the primary consumer who consumer the primary producer (Mills et.al. 1993). A common example of a keystone species that have been widely studied is sea otters, which typically live in tidal areas off the coast of West Coast of the United States and Alaska.
Sea otters, or Enhydra lutris, are keystone species to kelp forests because of their importance in maintaining the food web structure. They are top marine predators that are easy to observe because they live close to the shore (Laidre and Jameson 2006). They are carnivores because their average diet consists of benthic invertebrates such as sea urchins, turban snails, red urchins, bivalves and chitons (Duggins 1980). Otters typically have an up to thirty percent daily nutritional requirement of their body mass per day (Laidre and Jameson 2006). They prefer to eat urchins because it allows them to maintain their high metabolism (Laidre and Jameson 2006). The preferred prey for otters is sea urchins, Strongylocentrotus spp., because they offer the otters a high caloric intake per urchin eaten. These sea urchins consume a lot of algae and have the capability to eat large amounts of the kelp forests (Estes and Palmisano 1974) and are considered the primary consumers in the community structure. Sea urchins are able to last a long time with a reduced food intake through several adaptations to their biotic and abiotic environment (Duggins 1980). .
A unique characteristic of sea otters is that they forage for their food in a number of different habitat types, ranging from rocky subtidal reefs to sand or mud-bottom estuaries (Laidre and Jameson 2006). Depending on which habitats they live in, sea otters will consumer whatever is closest to them. If they are found in rocky habitats, they will consume sea urchins, but if they are in the soft-bottom substrate, they will eat clams and other bivalves (Laidre and Jameson 2006).
Sea otters are responsible for maintaining the food web within the...