Just add otter

Aug. 23, 2023

Allen Protasio

From keystone species to key to the future

Southern sea otters are important members of the ecosystems where they live. Their presence along California’s central coast has bolstered kelp forest environments. Current research suggests these habitats have suffered losses elsewhere in the state where otters are absent. As the Monterey Bay Aquarium works to recover California’s sea otter population, we also look at the positive impacts their return can have for our coastline.

A crucial component to coastal habitats

Southern sea otters are the glue that holds important coastal environments together, healthy, and in balance. They’re a textbook example of a keystone species—organisms that have a big impact on their environment just by being there. In other words, without sea otters, these habitats would look drastically different.

Otters are top predators in kelp forests along the central coast of California. This habitat provides food, shelter, a nursery, and hunting grounds for many fish, marine mammals, seabirds, and other species. Sea otters hold a particular fondness for sea urchins—grazing animals that happen to be voracious consumers of the giant kelp and bull kelp that provides the physical structure to this marine home. Without sea otters, urchins can decimate huge swaths of kelp forest, with devastating effects on the entire ecosystem and all that depend on it.

Underwater view of a fish-eating anemone (Urticina piscivora) amidst other wildlife in a wild kelp forest near Monastery Beach — Kelp forest habitats support a wide variety of life. You can find communities of animals everywhere in a kelp forest, from the rocky substrate the kelp anchors itself and attaches to at the bottom of the ocean...

An underwater view of sunbeams shining through fronds of a wild kelp forest at Monastery beach — ... all the way up to the kelp canopy at the ocean's surface. This diversity of life is possible thanks to keystone predators like sea otters that help maintain the balance within the habitat.

Sea otters help buffer kelp loss

A study led by Aquarium researchers amplifies the significant role these marine mammals play within kelp forest habitats. Their impact on this ecosystem is especially striking when compared to kelp forests in other parts of the state where sea otters haven’t yet been able to reestablish their populations since the 18th- and 19th-century fur trade. Looking back over a hundred years of data by georeferencing historical maps covering the entire coast of California, we've found a sharp decline in kelp forest coverage in both southern and northern regions of the state. That doesn’t seem to be the case along the Central Coast, where the kelp canopy has shown notable growth during the last century. It’s no coincidence that sea otter populations are thriving here.

While we've seen the impact that sea otters have had on the local environment since our opening in 1984, this study's unique approach allowed us to highlight these important ecological relationships over a much larger time scale. Additionally, these results provide a strong link between recovering sea otter populations and kelp forest resilience to climate change.

A recent study led by Aquarium researchers has shown that kelp forest coverage along California's central coast has increased over the past 100 years. It's no coincidence that this area between Santa Barbara and Monterey Bay is where the southern sea otter population has made a recovery. In contrast, declines in coverage have been widespread across the northern and southern coasts of the state where sea otter populations have yet to reestablish. Reproduced with permission from Teri Nicholson, author, *Sea otter recovery buffers century-scale declines in California kelp forests*.

Looking ahead

It’s clear to researchers that the presence of sea otters has helped protect the nearshore marine environments they inhabit in California. Consequently, these regions have flourished, expanded, and witnessed a surge in biodiversity. As we continue our work to support the recovery of the southern sea otter population, we look forward to seeing how the return of sea otters will contribute to the recovery of other important habitats along our coast.

Love sea otters?

Our sea otter conservation efforts are possible thanks to otter lovers like you! By supporting our Sea Otter Program is unique, you'll have real impact on their survival and the coastal habitats they call home.

Help save sea otters