More Than Just Cute: The Significance of Sea Otters in Marine Ecosystems

By Kasandra Kutzer

You may think of sea otters, or Enhydra lutis, as cute and fun little creatures that bring joy to our oceans with their lovable faces and playful personalities. Well, you would be right! But there is much more to these animals and their impact on the ocean. Before we delve into that, though, you probably want to know the basics of these lovely creatures first. Sea otters belong to the family Mustelidae, and are related to other animals you may know and love, such as ferrets, weasels, and river otters. They are divided into three subspecies: Southern sea otters, Northern sea otters, and Russian sea otters. All three reach approximately 4 feet in length, but vary in weight. For example, female Southern sea otters weigh about 50 pounds and males weigh about 70 pounds, while female Northern sea otters weigh about 70 pounds and males weigh about 100 pounds. All subspecies of sea otters can be found in kelp forests, but each inhabits a different part of the globe. Russian sea otters live off the Eastern coasts of Japan and Russia, Northern sea otters live off the shores of Alaska and Washington, and Southern sea otters live off the coast of California. These subspecies all feed on urchins, abalone, mussels, clams, snails, and crabs; Northern sea otters will also prey on fish. The otters may acquire this prey by diving to the seafloor before swimming back to the surface to feed while floating on their backs. For prey with hard shells, the sea otters will even use rocks like tools to crack them open. The otters will have to find quite a bit of this prey, as they will need to eat 25% of their body weight each day. To help them achieve this efficiently, sea otters have skin folds under their arms that can act as pockets to store their food for easy access throughout the day. These otters also have the densest fur of all animals, which they use to regulate their body temperatures in the cold ocean water. To put this into perspective, they have ten times the hair that we have on our heads per square inch of their bodies! Unfortunately, these fascinating creatures have been classified as endangered. This classification is especially alarming considering the impact they have on our oceans.

The fact that sea otters are endangered is a huge problem because of the role they play in maintaining kelp forest ecosystems. Specifically, they are a keystone species, which means they impact the ecosystem they live in to an excessive degree compared to other animals. They do this by preying on sea urchins that would otherwise eat the kelp in a destructive manner. This is an example of a concept known as the trophic cascade, which refers to the considerable decline in an ecosystem’s flora as a result of increased herbivory in the absence of a predator. Not only do sea otters limit sea urchins from destroying kelp forests by controlling their population size, but their presence also pushes the urchins into hiding, where they will feed on dead kelp that drifts near them rather than live kelp. Otherwise, the urchins’ feeding habits would lead to a phenomenon called an urchin barren, where the kelp forest ecosystem can no longer sustain other life. 

There are many reasons that it is important to preserve sea otters and, thus, kelp forests. One such reason is that these ecosystems support populations of animals that rely on kelp. For example, a species of dugong that went extinct in the 1800s, called the Steller’s sea cow, needed kelp forests for nutrients. Incidentally, sea otters were being overhunted in the 1700s and 1800s for the fur trade. This led to the loss of many kelp forests via herbivory by urchins that were newly unchecked. Thus, some scientists believe that the Steller’s sea cow went extinct due to a lack of food availability resulting from the destruction of these ecosystems. By protecting sea otter populations, we could prevent living animals that rely on kelp forests from meeting the same fate as the Steller’s sea cow. For example, the preservation of sea otters could protect the food sources of animals that feed on kelp, such as turban snails, abalone, and bat stars. Conservation of sea otters could also protect animals that use kelp forests for shelter or as a habitat, like grey whales, seals, sea lions, and snowy egret birds. 

Another reason that kelp forests are important is because of the effect they have on our climate. The giant kelp found in kelp forests stores carbon that would otherwise pollute the air. In fact, scientists have found that when there are more sea otters present and thus more kelp present, there is almost thirteen times more carbon being sequestered than when sea otters are absent. It is important to note, however, that carbon sequestration by kelp alone has a minuscule effect on total atmospheric carbon. However, by preserving other keystone species that maintain ecosystems with carbon-sequestering plants, the effects could potentially add up. 

Kelp forests are also important because of their positive impact on our economy. For example, they support populations of fish species that are worth half a trillion dollars in the seafood industry worldwide. Kelp forests also support $70,000 worth of nitrogen sequestration per hectare per year. Additionally, these ecosystems contribute to tourism and community activity, due in part to the fact that 740 million people live within 31 miles of a kelp forest.

Sea otters are endangered because of the many threats they face. These include habitat pollution by oil and plastic, pathogens growing in algal blooms caused by chemical runoff, and ocean warming. These threats may be exacerbated by the passage of a recently proposed bill that would roll back the Marine Mammal Protection Act. This act helps mitigate threats to sea otters by preventing harm to marine mammals from the oil and fishing industries. 

You can help protect sea otters and kelp forests in many ways. For example, you can help reduce plastic pollution by replacing the disposable plastics that are part of your daily routine with reusable and non-plastic alternatives. You can also reduce oil pollution by switching to vehicles and other tools that use electricity instead of gasoline. To help prevent algal blooms that harm sea otters, you can reduce chemical runoff by switching to natural pesticides rather than chemical ones. Another way to contribute to sea otter conservation is by preserving the Marine Mammal Protection Act. If the bill that was proposed to remove this act is passed by the House committee’s July 22nd vote, then it will be voted on by the full House of Representatives. In this case, you can help block this bill by contacting your House representative, who you can find here. You can also help protect sea otters by donating to organizations that participate in their conservation, such as the Monterey Bay Aquarium and the Sea Otter Foundation and Trust.

By taking part in the conservation of sea otters, you aren’t just protecting cute faces and the joy they bring to ocean-lovers everywhere. You’re also protecting important kelp forest ecosystems and the species they support. Preserving such biodiverse and impactful environments creates a ripple effect that protects even more of our oceans and our world.

Citations

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2. Estes, J.A., Burdin, A., Doak, D.F. (2015). Sea otters, kelp forests, and the extinction of Steller’s sea cow. Proc. Natl. Acad. Sci. U.S.A., 113(4), 880-885. https://www.pnas.org/doi/epdf/10.1073/pnas.1502552112. 

3. Michel, C. (2025, July 8). New Bill Would Gut Marine Mammal Protections. Defenders of Wildlife. https://defenders.org/newsroom/new-bill-would-gut-marine-mammal-protections. 

4. Monterey Bay Aquarium. (2020, March 10). Kelp forest. Monterey Bay Aquarium. https://www.montereybayaquarium.org/animals/habitats/kelp-forest. 

5. Monterey Bay Aquarium. (2020, March 10). Sea Otter. Monterey Bay Aquarium. https://www.montereybayaquarium.org/animals/animals-a-to-z/sea-otter. 

6. National Human Genome Research Institute. (2024, February 8). How a bill becomes a law. National Institute of Health. https://www.genome.gov/about-genomics/policy-issues/How-Bill-Becomes-Law.

7. Sea Otter Foundation and Trust. (2025, June 11). The Future of Sea Otters: What 2050 Could Look Like for These Ocean Guardians. Sea Otter Foundation and Trust. https://seaotterfoundationtrust.org/the-future-of-sea-otters-what-2050-could-look-like-for-these-ocean-guardians/. 

8. Wilmers, C.C., Estes, J.A., Edwards, M., Laidre, K.L., Konar, B. (2012). Do trophic cascades affect the storage and flux of atmospheric carbon? An analysis of sea otters and kelp forests. Frontiers in Ecology and the Environment, 10(8), 409-415. https://doi.org/10.1890%2F110176.