Months after mass death of sea creatures in British Columbia’s thermal dome, researchers return to search for signs of life

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At the height of British Columbia’s heat dome in June 2021, Chris Harley, a professor in UBC’s Department of Zoology, traveled to West Vancouver’s Lighthouse Park to measure water temperatures and observe how the marine animals that inhabit the coasts of British Columbia behaved in extreme conditions.

He expected to see some degree of mortality, but instead he was greeted by the overwhelming stench of rotting flesh as the sea creatures cooked in the open, their shells cracking open.

In the days that followed, Harley and his students estimated that billions of sea creatures had died as temperatures soared above 40°C and water temperatures reached 56°C.

Ten months after the BC coastal disaster, researchers combed back BC beaches, looking for signs that vital populations of native seaweed, crustaceans and shellfish the coast are experiencing a resurgence.

“There’s reason to be optimistic. Seeing the tiny juvenile barnacles arriving is a good sign. But the system has been disrupted,” said Harley, who has been studying West Coast shorelines since 1995.

“Yesterday I was closer to White Rock and it still looks like a bomb went off there – lots of death and destruction.”

Harley said while the ecosystem is showing promising signs of resilience, it is now particularly vulnerable to the dangers of another heat dome. And the collapse of one population has cascading effects on others. For example, many rocks that were usually smooth green and brown with algae are now bare, leaving baby barnacles exposed to the sun.

“Once all the species are back, we know that a diverse ecosystem is more resilient to that kind of insult. But if you get another big disturbance, another big heat wave before the ecosystem has a chance to recover, it may actually do more damage than it otherwise would have,” Harley said.

Harley and his students surveyed the coasts from Victoria to Sooke and White Rock, and as far north as Bamfield, Puget Sound and the Strait of Georgia. They measure the number of sea creatures that repopulate by randomly searching the quadrants – laying out a square and counting the creatures that fall into it, then increasing to estimate mortality.

Early findings indicate that mobile species had a higher survival rate, thanks to their ability to find shade and cooler enclaves. But those anchored to rocks, such as starfish and crustaceans, fared less well. Barnacles and mussels planted on the north sides of the rocks have often survived, while those on the south side of the rock have in many places disappeared entirely.

Ten months after the disaster on British Columbia’s coast, researchers returned to comb its beaches, looking for signs that vital populations of seaweed, barnacles, mussels, starfish and crabs native to the coast are experiencing a resurgence. (Gian Paolo Mendoza/CBC)

Harley warns that BC’s beaches and waters will transform if species like mussels and barnacles are replaced by populations that thrive in warmer temperatures.

“Mussels and barnacles filter out a lot of the gunk in the water. What would False Creek look like if we lost those filters or replaced them with something that might work a little differently? There are questions we didn’t even think to ask until last summer because we didn’t expect this kind of thing to happen so quickly,” he said.

“I think in five, 10, 15 years it will be, instead of a mussel-dominated shoreline, it will be more of an oyster-dominated shoreline. And it might actually look like subtropical parts of Asia of the East. at this time.”

Harley and her students aren’t the only group studying the impact of climate change on the waters off British Columbia.

William Cheung, a marine biologist at UBC, analyzed 340 Vancouver-area restaurant menus between 1880 and 2021 as he researched other datasets to determine how climate change will affect fish populations.

His research, which also looked at restaurant menus in Anchorage and Los Angeles, found that the preferred water temperature of seafood served to diners is getting hotter and hotter.

“We have seen a significant increase in the temperature of seafood that restaurants have been serving since the 1980s,” Cheung said.

“One of the interesting things is that the increase is closely related to changes in seawater temperature, as well as the composition of species that fishermen catch according to temperature changes during this period. “

William Cheung, a marine biologist at UBC, analyzed 340 Vancouver-area restaurant menus between 1880 and 2021 as he researched other datasets to determine how climate change will affect fish populations. (Gian Paolo Mendoza/CBC)

Cheung said Humboldt squid, a hot-water species, was barely on restaurant menus before the 1990s, but has appeared with increasing frequency in recent years. He also predicts that sardines, a warm-water species that faced a population crash in the 1950s, will once again become a staple on restaurant menus in British Columbia as they swim upstream to warmer waters. hotter.

But salmon, a favorite of many British Columbians, may be much less available in the near future as it faces habitat collapse.

“People might think the effects of climate change in the oceans are far away, but our study shows that climate change affects everyone,” Cheung said.

Harley said he hopes the barnacle and mussel populations have proven resilient, but he remains concerned about the potential for another dangerous heat wave in 2022.

The analogy I use is that when you get sunburned, it’s bad. If you get a second sunburn before the first heals, you are more likely to get skin cancer. And the system hasn’t healed yet,” he said.

“I think environmentalists like me are a bit caught off guard because things are changing faster than expected.”

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