California kelp forests are the most diverse ecosystem of the temperate latitudes on earth. Sea otters do not cause the local extinction of species. Abalone numbers are often high within the sea otters range. However, the abalones are restricted to deep crevices, out of reach of otter and human harvesters. It is a widely accepted ecological concept that the more diverse and complex an ecosystem, the more stable it is.
Sea otters are an indicator of the health of the nearshore marine ecosystem.
The sea otter tends to be relatively sedentary in comparison to other marine mammals. The sea otter eats a wide variety of foods. The sea otter is closely related to mink, a carnivore with established sensitivities to contaminants. High levels of other contaminants, such as PCB, are also found in sea otter tissues. The sea otter is an umbrella species.