Sea Otters Are Warriors of Carbon Devouring Kelp Forest

A large population of sea otters have a strong influence on the cycle of carbon storage, procesing and global warming. According to a new study done by two UC Santa Cruz researchers , the sea otter population that keeps sea urchins in check will indirectly allow kelp forests to grow.

According to the study released online Sept 7 in the Frontiers in Ecology and the Environment, the increase in the kelp forest can absorb as much as 12 times the amount of carbon from the atmosphere. But Sea urchins eat kelp plants. However, to keep sea urchin under control it is necessary to have sea otters. The sea otters feast on sea urchins and in turn protect the kelp forests.

"It is significant because it shows that animals can have a big influence on the carbon cycle," said Wilmers, assistant professor of environmental studies and one of the lead authors.

Nearly 40 years of data was combined by Wilmers, Estes: a professor of ecology and evolutionary biology and their co authors. The data was based on otters and kelp from Vancouver Island to the western edge of Alaska's Aleutian Islands. 

On analyzing the data the researchers have noticed that otters undoubtedly have a strong control on the cycle of carbon storage.

The researchers compared kelp density under the influence of otters and also without the otters; they saw that, "sea otters have a positive indirect effect on kelp biomass by preying on sea urchins, a kelp grazer." 

In the presence of sea otters the urchins disappear inside the gaps and feed on kelp scraps. But in the absence of sea otters, sea urchins nibble on living kelp.

Kelp has a great potential to absorb carbon through a process called photosynthesis. Increase in the CO2 concentration results in global temperatures to rise.

The researchers argue that, "Spreading otter population won't solve the problem of higher CO₂ in the atmosphere but argue that the restoration and protection of otters is an example how managing animal populations can affect ecosystems abilities to sequester carbon."

"Right now, all the climate change models and proposed methods of sequestering carbon ignore animals," Wilmers said. "But animals the world over, working in different ways to influence the carbon cycle, might actually have a large impact.

"If ecologists can get a better handle on what these impacts are, there might be opportunities for win-win conservation scenarios, whereby animal species are protected or enhanced, and carbon gets sequestered," he said.