Rochelle Baker, Local Journalism Initiative – June 8, 2022 / 20:15 | History: 371375
Photo: Brooke Hatfield / Canada’s National Observer
Researcher Sam Starko examined how the sea heat wave, The Blob, affected algae populations to the sound of Barkley, off the coast of BC.
BC’s critical kelp forests have withered as climate change has caused sea heat waves along the entire west coast in recent years.
But exceptions to the rule may provide useful information for saving and restoring our underwater forests, said Samuel Starko, a researcher at Victoria University.
Kelp’s forests don’t all respond in the same way to extreme sea heat incidents, such as the two-year event that began in 2014 ominously known as “The Blob,” Starko said.
During the blob event, water temperatures along the Barkley Sound coast rose to 3 ºC, sometimes reaching 20 ºC, temperatures more typical of Southern California waters, Starko said.
Kelp populations at the entrances and sound fjords off the west coast of Vancouver Island disappeared in 40% of the sites analyzed due to abnormally warm waters, a Starko-led study showing historical data from the Center showed. of Bamfield Marine Science.
Kelp forests, which span more than a third of the world’s coasts and thrive in cooler waters, are one of the most endangered marine habitats from global warming, Starko said.
“Kelp forests are really among the most productive and abundant ecosystems we have off the coast of British Columbia,” he said.
“Therefore, 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 act as fishponds for important species such as salmon, cod and cod, and as a habitat for all kinds of fish and marine mammals, such as seals, sea otters. Gray whales also rely on algae forests for abundant krill.
The impacts on algae in warmer inland coastal waters were spectacular and algae populations have not recovered so far, especially considering a second, less dramatic drop hit the coast again in 2019.
Perhaps not surprisingly, kelp forests in the cooler waters of the outer coast suffered fewer losses. And some populations survived along the interior of Barkley Sound if they were in deeper, colder waters, which experienced a good mix of water through wind or tides, Starko said.
Uncontrolled sea urchins chew algae forests
But another impact on the survival of kelp forests is sea urchins, which, if left unchecked, can devour marine gardens and leave underwater outcrops in their path.
The drop had a double effect, Starko said. The warmer water also aggravated a wear and tear disease that has decimated the previously ubiquitous sunflower starfish, a key predator of sea urchins.
Without pressure from their traditional predator, sea urchin populations exploded and also negatively affected algae.
But the study found that algae forests in deeper, cooler waters were more likely to survive if they grew at the bottom of a sandy ocean instead of rocky places that hedgehogs usually prefer, Starko said.
The findings of the study and the like could help scientists, first nations, governments and conservation groups collaboratively design plans to save and restore algae gardens, Starko said. that a new center called the Kelp Rescue Initiative has been set up to try to facilitate these 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 collect sea urchins in areas that help protect algae forests, he added.
Also working to identify which types of BC kelp are most resistant to warm temperatures and replanting them in areas with ideal conditions that hedgehogs do not find attractive is another possible restoration method, he said.
The diversity of algae on the BC coast is unmatched and offers unique opportunities for research and restoration, he said, adding that a quarter of all algae species are found on the Pacific coast of America. of the North.
“We have this interesting mix of northern species that are most 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 its evolution actually took place (along the west coast) and spread from there to the rest of the world. ”
But sea heat waves, which have prolonged and abnormally high water temperatures due to changes in weather patterns and ocean behavior, are different from the dome of atmospheric heat and the record temperatures experienced by BC l last summer.
A week or so of extremely hot weather could kill algae exposed to the shallow waters of the intertidal zone, but it would not dramatically affect algae in deeper waters, Starko said.
“The ocean water didn’t really heat up as much as it did during the drop,” he said.
There are still many outstanding research questions about algae along the coast and how marine ecosystems in specific places are resisting climate change, Starko added.
“I really think they are the underwater equivalent of rainforests,” he said.
“And I find it really exciting … to investigate such an important group of organisms that we know so little about.”