Sea otters are adorable. New research published in the Nature journal found that beyond being really cute, they also play an important role in suppressing erosion of marsh edges.
Researchers focused on otters in the Elkhorn Slough estuary, located in Elkhorn, Calif. According to UC Santa Barbara’s The Current, data on erosion in the salt-marsh slough dates back to the 1930s and “and meticulous sea otter counts exist from the 1980s onward” since the species began to recolonize the habitat.
“The California sea otter, once hunted to the edge of extinction, has staged a thrilling comeback in the last century,” said a report published this Thursday by NPR. At the same time, the Elkhorn is still threatened by nutrient loading, hydrological change and sea-level rise.
While sea otters may look sweet and cuddly, researchers noted that they are actually the top predator of the estuary. Their return to the area is linked to what the scientists call a “trophic cascade that facilitates coastal wetland plant biomass and suppresses the erosion of marsh edges.”
Per the study, that erosion process can lead to severe loss of habitats and ecosystem services.
“These top predators can have a large effect on the habitats that they exist in. But we don’t know what those effects are unless we directly test them,” explained co-author Kathryn Beheshti, an assistant researcher at UC Santa Barbara’s Marine Science Institute.
In particular, the researchers discovered that sea otters in the central California estuary suppressed the abundance of burrowing crabs. This in turned helped bolster marsh edge strength.
“In the cold, estuarine waters of Elkhorn Slough, sea otters consume more than 25% of their body weight (around 10 kg of prey) daily to maintain sufficient metabolic functioning,” they said. In marsh tidal creeks, sea otters focus their foraging mainly on invertebrates, including the shore crab.”
Even though the sea otter populations in the Elkhorn Slough estuary are recovering, it is “experiencing intense physio-chemical stress owing to human activity,” the study authors explained. As the otters rebound, they could continue to make the area more resilient.
“These results show that trophic downgrading could be a strong but underappreciated contributor to the loss of coastal wetlands, and suggest that restoring top predators can help to re-establish geomorphic stability,” said the study.
Researchers also believe that these observations may be applied to other areas where top predator populations have been reduced.
“Beyond coastal wetlands, this work has implications for theoretical and applied understanding in ecology, geomorphology and conservation,” they said. “In ecology, our study is a robust demonstration that recovered top predators can transform plant communities, consumer assemblages and geomorphic processes, leading to the resistance of ecosystems to anthropogenic stressors.”