Crushing heat wave in Pacific Northwest and Canada cooked shellfish alive by the millions

Amid the crushing summer heat wave that slammed the Pacific Northwest and parts of Canada, Alyssa Gehman, a marine ecologist who lives by the sea in Vancouver, walked down to the shore to go for a swim. As expected, the beach was packed with others looking to beat the heat wave.

She made her way to the edge of the water. It smelled like putrid shellfish - cooking.

All around her, beds of mussels had popped open, dead. The heat beating down on the rocks had killed them, and she could see dead tissue between their shells.

A dead crab floated in the water, she said.

Gehman studies marine community ecology, but this was the first time she had seen anything of this “magnitude of mortality.” An estimated 1 billion small sea creatures - including mussels, clams and snails - died during the heat wave in the Salish Sea, off more than 4,000 miles of linear shore, according to marine biologist Chris Harley.

The end of June in the Pacific Northwest saw record-breaking temperatures, reaching an all-time high in British Columbia of 121 degrees. British Columbia reported at least 486 “sudden and unexpected deaths,” which is hundreds more than the average number of deaths over a five-day period.

Harley’s research team used infrared cameras to measure temperatures on the shoreline rocks, recording some readings as high as 122 degrees.

With mechanisms to keep from drying out, mussels are able to withstand high temperatures. They hold water inside their shell and close up on land, when exposed by tides. They grow in beds, which provide a thermal buffer. But the record heat was just too much.

The Harley Lab at the University of British Columbia is looking into the mass mortality event on the shore, and trying to determine just how many animals died, how animals that survived were affected, how it happened and how likely it is to happen again.

The heat also affects businesses. Many shellfish farms on coastal regions were hit by historically hot temperatures.

Hama Hama Oysters, a fifth-generation family-run oyster farm in Washington, in a post on Instagram, said that their dead shells were “impressive in number.” Putting on a brave face and turning to humor, a post described the impact on the business’s clam beds in Hood Canal as “clamitous.”

Experts warn that climate change is driving changes in weather, including heat waves. “Extreme weather events are getting more frequent and climate change has a significant role to play in that,” Canadian Prime Minister Justin Trudeau said earlier this month.

“Please vote for politicians who are brave enough to address climate change,” the Hama Hama oyster farm urged on social media.

Losing mussels and other bivalve mollusks like oysters and clams can throw off the entire ecosystem, Washington-based marine biologist Emily Carrington told The Washington Post. Shellfish perform critical ecosystem services, modifying their local environment just by their presence and aggregation. They filter a high volume of water and play a central role in the food chain, she said

Harley said she thinks the mass loss of shellfish could serve as a “wake-up call.”

“The pandemic was a big scary, intimidating problem and most of us were willing to make a few small changes that really helped,” he said. “We can do the same thing with climate change.”