By Ula Chrobak September 15, 2021 Sea otters were hunted until On the edge of the 19th century fur trade, but their numbers have slowly risen since. The return of these playful creatures not only transforms their ecosystems, it can turn them into a powerful carbon sink. S
Sea Otters are creatures steeped in superlatives.
Enhydra lutris is the hairiest animal on Earth, with up to 140,000 hairs on every square inch of her body, which means her hair is 700 times denser than that of a head human. Unlike many other marine mammals, they lack fat, so they keep warm by eating a quarter of their body weight per day. Sea otters also play a unique role in supporting the ecosystems of kelp forests in the North Pacific.
Few other animals eat as much for their weight or play such a crucial role in it. maintaining their environment, says Brent Hughes, a marine ecologist studying coastal habitats at Sonoma State University in California.
Now scientists are studying how this marine data mustelids can also be superheroes of the climate. Sea otters help ecosystemsSystems to capture carbon from the atmosphere and store it as biomass and deep-water litter, preventing it from being converted back to carbon dioxide and contributing to climate change.
Sea otters were once widespread in the coastal waters of the North Pacific Ocean, from Baja California to Alaska, to rocky reefs in Russia and Japan. However, in the 1700s and 1800s, the fur traders hunted their population until about 2000 animals . Since then, the conservation efforts have enabled otters to bounce somewhat, but some 2,500 miles (4,000 km) of coastline in their historic range are still devoid of furry mammals.
This loss of otters demonstrated their role iIndispensable in kelp forests. While diving in the Aleutian Islands of Alaska in the 1970s, James Estes, a marine ecologist at the University of California at Santa Cruz, documented that kelp forests without sea otters essentially become underwater deserts. . In contrast, in areas where otters live, kelp has thrived, as has the persified aquatic community that feeds and shelters among algae. "Just in my own soul, that was an important thing," he said of his first observations on this glaring difference. "I felt like I had learned something quite remarkable.
The key to this difference is the voracious appetite of sea otters. In order to keep their bolic rates high, mammals must eat constantly. Among their favorite foods are sea urchins, which are easy to catch and high in calories. When present, sea otterseat so many sea urchins that the invertebrate population remains low. "They have a disproportionate impact on the ecosystem compared to their abundance," says Heidi Pearson, marine biologist at the University of Southeast Alaska. This is what makes them a "keystone " species - without their presence the stability of the entire ecosystem can be lost.
Sea otters have a voracious appetite, eating about a quarter of their body weight each day (Credit:)
When sea otters disappear from an ecosystem, sea urchins are increasing. Herbivorous sea urchins then clear cut the kelp, chewing on the seacrawling to their base and sending the rest of the giant algae to wash. With this goes the habitat of many species, including fish, invertebrates and other mammals.
Sea urchins remain even after cutting through kelp beds. They go into a state of sleep, biding their time under new kelp shoots, then spring into action to eat the young algae. These invertebrates are known as "zombie sea urchins" for this ability. If the sea otters return, however, their feast may put the herbivores in check and allow the kelp to thrive again.
But these perpetually hungry mammals don't just protect ecosystems. of kelp. Sea otters can also enjoy seagrass beds. In these areas, otters feed primarily on crabs. When mustelids reduce the number of crabs, the grazing organisms that crabs eat reboundfeels. These slugs and snails often do not eat seagrass beds; instead, they scrape off the algae that grows on the grass, allowing the algae to absorb more sunlight and grow more efficiently. “They don't miraculously eat the seagrass beds,” says Hughes. "They have this little radula that gently scratches [the algae] and removes any epiphytes that grow on it. And so it basically protects the algae.
In the Elkhorn Slough estuary in California, eelgrass was nearly extinct by the early 1980s due to declining water quality - nutrient pollution from farms increased algae growth, choking seaweed. But since the return of the otters, the eelgrass has grown by more than six times .
And in these two ecosystems, otters couldt have the added benefit of storing carbon.
In 2012, a team of environmentalists including Estes published a study on the carbon sequestration potential of sea otters in the North Pacific between the Aleutian Archipelago and Vancouver Island. Using data on kelp growth rate and density at sites wi th and without otters, they found that the presence of sea otters in the rock reef habitat in the area of study, covering 51,551 square kilometers (19,900 square miles - an area roughly the same size as Costa Rica), is able to store 4.4 to 8.7 million tonnes of carbon compared to if an otter- free state. This is more carbon than that emitted by a million passenger cars for a year.