Sea urchins are prickly “hedgehogs of the sea” that exist in every ocean around the globe.
You might have seen their spines peeking out of the water during low tide — or even stepped on one while swimming — but their presence in small numbers is good for the environment. They graze on algae, which helps coral reefs thrive.
But it is true that you can have too much of a good thing.
When sea urchins overpopulate the sea floor, they mow down any algae and kelp in their path, even destroying entire kelp forests.
These forests under the sea serve as protection for over 1,000 species of fish, crustaceans, and invertebrates (including sea stars, anemones, and jellyfish).
When kelp forests disappear, the animals that live amongst them disappear in turn, taking critical food resources away from bigger marine life like sea lions and whales.
There’s even a climate cost to losing kelp forests, now that scientists have discovered that kelp forests temporarily store roughly 20 times more carbon per acre than woodest forests on land.
Fortunately, sea otters have emerged as the unsuspecting heroes of the sea. By snacking on sea urchins, they keep urchin populations in check.
Which is good, because sea otters are pretty hungry for fluffy, four-foot long carnivores.
To stay warm (without the blubber that other sea mammals have built in) sea otters eat a quarter of their body weight in food every day. In addition to sea urchins, they eat crabs, sea snails, clams, mussels, and slow moving fish.
To crack open their hard-shelled prey, otters will forage for sharp-edged rocks (and store them in their ‘armpits’ when they dive) to use them like anvils to open food up. Sometimes they can even rip dinner apart with their dexterous little paws.
But researchers are slowly realizing more and more just how important sea otters are to the environment.
In fact, researchers pored over a century of ocean maps and proved that wherever sea otters live — and have lived — the ocean has been better for it.
In the study, published in PLOS Climate, lead researcher Kyle Van Houtan said than increased otter conservation — and less human activity — “can have an impact which cascades through the ecosystem.”
Marine ecologist Brent Hughes has studied otters impact on the environment, especially in the area between Monterey and San Francisco.
He says another way that otters help the ocean is by feeding on destructive shellfish like the striped shore crab. Those crabs dig into mud and sand along the shore line, eating pickleweed and leaving marsh grass areas looking like “swiss cheese.” This, in turn, increases coastal flooding.
“[Otters] don’t completely reverse erosion but slow it down to natural levels,” Hughes explained to VOA News.
To keep the ocean thriving, in a number of ways, conservationists want to help sea otters thrive too.
There are three subspecies of otters: the “California” sea otter (or southern sea otter), the northern sea otter, and the Russian sea otter.
While the Russian sea otter species is considered stable, the California sea otter is listed as endangered under the Endangered Species Act, and a subsect of northern sea otters are listed as endangered off of the coast of Alaska.
Fortunately, sea otters have been making a comeback in California, and the ripple effect is extraordinary.
In a scientific study published in Nature, a team of conservationists and marine ecologists concluded that sea otters’ reintroduction to the Central California slowed erosion of the area’s creekbanks and marsh edges by 69%.
“In this instance, restoring the otter population was achievable through sustained conservation efforts, and as a result, we are now unlocking several decades of benefits,” said Christine Angelini, one of the authors of the study.
This specific conservation effort to save California sea otters stretches back to the 1980s, and marine biologists couldn’t be happier about the study’s resounding success.
“It would cost tens of millions of dollars for humans to rebuild these creekbanks and restore these marshes,” Brian Silliman, marine biologist at Duke University’s Nicholas School of the Environment, told Center for Coastal Solutions.
“The sea otters are stabilizing them for free in exchange for an all-you-can-eat crab feast.”
For Angelini, climate change challenges and broad species decline can sometimes feel “unsurmountable.”
But research like this gives her hope.
“This study indicates to us that, if we truly understand the ecosystem and know what levers to pull, we can see significant benefits to the health and stability of these systems,” Angelini said.
Header image via Wade Tregaskis (CC BY-NC 2.0)
