Dead mussels at the waterline
Rivers & Oceans, Weather

A billion marine creatures may have perished in the heat

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CKTZ News, Local Journalism Initiative Reporter

Close to a billion marine creatures may have perished in BC’s recent heat wave. 

What happened? 

“We had some of the hottest weather we’ve ever had and it happened to be on days with very low, low tides and that combination was pretty lethal for a lot of things,” explained Dr Chris Harley, a marine biologist at the University of British Columbia.

He said the one billion death estimate was obtained through calculations of mussel populations.  

“The numbers are really large because there were a lot of mussels to start with,” he said.

Harley has been receiving numerous reports of marine life die-offs in the 650 kilometres of coastline, as the crow flies, between Klemtu, BC, and the Hood Canal, in northern Washington.

For many Cortes Island residents, the first they heard of these deaths may have been when local shellfish grower Erik Lyon was interviewed by the CBC. He reported losses of between 5% and 20% on a comparatively wet site in Desolation Sound, but expected to see higher mortality rates elsewhere.

There also appear to have been an abnormally high number of shellfish deaths at a number of Cortes Island locations.

Ricky Belanger, from the Discovery Passage Aquarium in Campbell River, reported seeing high numbers of dead cockles.  

Harley said that mussels in the shade, or on a north facing surface, were probably okay. So were the oysters grown on rafts. 

Large numbers clams, cockles and mussels perished on beaches. 

A billion marine creatures may have perished between Klemtu and the Puget Sound
Map of areas mentioned in this article compiled by Roy L Hales

What does this mean? 

It is not certain what effect the heat wave will have on the health of surviving shellfish. One of Harley’s students, Graham Brownlee, found that if California mussels experience enough warm days, they are likely to survive when temperatures grow hotter. 

“The problem is that if it becomes so hot that they become stressed, and there is some internal damage that they suffer, then they are more vulnerable to all kinds of things. So the next hot day might be worse than if they had not already been compromised; they might be more vulnerable to predators, or pathogens, because they have been compromised,” said Harley. 

One of the big mysteries of climate change ecology is, “How often does a little bit of heating make you robust and able to do better? And how often does a little bit of heating set you up for failure when the next stress arrives?”

Harley said he has seen smaller heats waves. He witnessed a mussel die off north of San Francisco in the early 2000s. There was another one in Bamfield, on Vancouver Island. 

Dr Chris Harley examining some of the estimated billion marine creatures that perished during the recent heat wave
Dr Chris Harley examining mussels in the Vancouver area – photo courtesy Chris Harley

How this die off was unique

However this die off is unique because of:

  • the unprecedented high temperature for this time of year. 
  • the number of marine animals, and variety of species,  that died
  • the extent of the shoreline impacted, both close to the water and high on the shore. 

“I’ve now talked to a number of people who live around Vancouver, on Vancouver Island and the Gulf Islands, and the long time residents are all saying, ‘Oh, I have never seen anything like this in 30 years; or I’ve never smelled anything like this in 30 years … In terms of the longer term implications, it comes down to how often we might see these events, how severe they are, and I think climate change is really loading the dice against us,” said Harley. 

Things like mussels recover fairly quickly and he hopes to see them back on the shores of Vancouver and West Van as early as next year or the year after. Clams may take longer top recover. 

“If the time it takes to recover takes longer than the time between heatwaves, that’s when you start to see really big ecological changes,” he said. 

a dead seastar
Dead Sea Star – courtesy Dr Chris Harley

Climate Change

Harley was hesitant when asked if this could lead to the extinction of entire species, but conceded it was at least a a possibility.

He added, “It is also possible things will just be forced to move further north.”

Air temperatures in the Salish Sea are warmer than the outer coast of Oregon or Washington. Harley said that as climate change takes hold, the west coast of Vancouver Island may start to look like the Pacific Northwest of America, but you will have to go far further south to Southern California, or even Mexico, to find replacement species for Victoria or Campbell River.

“It is unlikely that those species are going to swim here, or drift here as larvae, so we don’t have the species replacements,” he explained.   

“For me as an ecologist and a concerned person, the silver lining in this is the fact people are interested. They are noticing. This gives me some hope that people are still interested in nature,” said Harley.

He points to the Global response to the COVID epidemic as proof that the world could take steps to lower their emissions, if they decide to.  

 

Dead mussels at Bowen Island – courtesy Dr Chris Harley

Top photo credit: Dead mussels at the waterline. Photo courtesy Dr Chris Harley

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