BC’s kelp is in hot water, but science can help save our underwater rainforests – Oak Bay News

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Vancouver Island’s kelp forests have responded in a variety of ways, according to a University of Victoria study. Photo without splatter/contributed

British Columbia’s critical kelp forests have withered as climate change has triggered marine heat waves along the entire west coast in recent years.

But exceptions to the rule can provide useful information to save and restore our underwater forests, said Samuel Starko, a researcher at the University of Victoria.

Kelp forests don’t all react the same way to incidents of extreme marine heat, like the two-year event beginning in 2014 ominously known as “The Blob,” Starko said.

During the blob event, water temperatures along the Barkley Sound coastline rose 3°C, at times reaching over 20°C, temperatures more typical of Southern California waters, said Starko.

Kelp populations in the inlets and fjords of the Strait off the west coast of Vancouver Island have disappeared at 40% of sites surveyed due to abnormally warm waters, a study by Starko examining historical data has shown. from the Bamfield Marine Sciences Centre.

Kelp forests, which span more than a third of the world’s coastline and thrive in cooler waters, are one of the marine habitats most at risk from global warming, Starko said.

“The kelp forests are truly some of the most productive and abundant ecosystems we have on the BC coast,” he said. “Thus, understanding how and where these ecosystems are vulnerable to warming and heat waves can help us better predict future changes and also improve our ability to conserve and restore these habitats.”

Kelp forests serve as nurseries for important species such as salmon, rock cod and lingcod and habitat for fish of all kinds and marine mammals, such as seals, sea otters. gray whales also depend on kelp forests for abundant krill.

The impacts on kelp in warmer inland coastal waters have been dramatic, and kelp populations have not recovered to date, especially as a second, less dramatic drop hit the coastline again in 2019.

Perhaps unsurprisingly, kelp forests in the cooler Outer Coast waters suffered less loss. And some populations survived along the inner parts of Barkley Sound if they were in deeper, cooler water, which experienced good water mixing by wind or tides, Starko said.

Left unchecked by predators such as sunflower starfish or sea otters, sea urchins can turn a kelp forest into an arid undersea. File photo by Grant Callegari / Hakai Institute

But another impact on the survival of kelp forests is sea urchins, which, if left unchecked, can devour sea gardens and leave underwater barrens in their wake.

The drop had a double effect, Starko said. The warmer water has also worsened a debilitating disease that has decimated the once ubiquitous sunflower starfish – a key predator of sea urchins.

Without pressure from their traditional predator, sea urchin populations exploded and negatively impacted kelp as well.

But the study found that kelp forests in deeper, cooler water were more likely to survive if they grew on a sandy bottom rather than rocky sites typically favored by sea urchins, Starko said.

Findings from the study and others like it could help scientists, First Nations, governments and conservation groups collaboratively develop plans to save and restore kelp gardens, Starko said, noting that a new center called Kelp Rescue Initiative has been set up to try to facilitate such projects. .

Keeping sea urchins under control could involve encouraging or protecting the natural expansion of sea otters, which also eat sea urchins, Starko said. Or harvesting sea urchins from areas that would help protect kelp forests, he added.

Also working to identify the types of BC kelp that are most resilient to hot temperatures and replanting them in areas with ideal conditions that sea urchins don’t find attractive is another possible restoration method, he said. declared.

The diversity of kelp on the British Columbia coast is unmatched and offers unique research and restoration opportunities, he said, adding that a quarter of all kelp species are found along the coast. Pacific of North America.

“We have this interesting mix of northern species that are more commonly found in Alaska and southern species that are found in California,” Starko said.

“That’s why we’re really at the center of their diversity. Much of their evolution actually happened (along the west coast) and they spread from here to the rest of the world.

But marine heat waves, which are characterized by prolonged and abnormally high water temperatures due to changes in weather patterns and ocean behavior, are distinct from the atmospheric heat dome and record temperatures recorded by Colombia. -Columbia last summer.

A week or two of extremely hot weather could kill exposed kelp in the shallow waters of the intertidal zone, but it wouldn’t have a dramatic impact on kelp in deeper water, Starko said.

“The ocean water didn’t get as warm as it did during the blob,” he said.

There are still many open research questions about kelp along the coast and how marine ecosystems in some places are resilient to climate change, Starko added.

“I really think of them as the underwater equivalent of rainforests,” he said.

“And I find it really exciting…to research such a large group of organisms that we know so little about.”

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