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Pacific Northwest and Canada’s Crushing Heat Wave Cooks Millions of Sea Creatures

The estimated death toll could be more than a billion

A healthy crop of mussels lines the coast, exposed during low tide. Mussels will split open when they overheat, such as in June's heat wave. (MediaNews Group/Orange County Register via Getty Images)
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During late June’s heat wave in the Pacific Northwest and parts of Canada, sea creatures on the coast were cooked alive by the millions in the scorching heat. Beach goers, some who had headed to the water to cool off, were greeted with putrid stench of shellfish baking in the sun.

“I was pretty stunned,” says Chris Harley, a marine biologist at the University of British Columbia, to the CBC's Alex Migdal. On Vancouver’s Kitsilano Beach where Harley stood, tens of thousands of dead mussels, clams, sea stars, barnacles and snails blanketed the sea rocks as far along the coastline as his eye could see. In particular, the mussels had split open, their freshly baked flesh still nestled inside.

Temperatures soared to a record-breaking 121 degrees Fahrenheit in British Columbia that weekend. Harley’s team used infrared cameras to measure similar temperatures on the rocky shoreline where the sea creatures once lived. Harley estimates the death toll of seashore animals along the Salish Sea coastline is over a billion.

Mussels spend their whole lives rooted in one spot on the edge of the coast. As the tides rise and retreat, they become submerged underwater or exposed to direct sunlight. At low tide, mussels on land snap shut and retain a small puddle of water in their shells so as not to dry out, reports Sammy Westfall and Amanda Coletta for the Washington Post. Normally, the water they hold should be enough to act as a thermal buffer, so they can tolerate temperatures around 90 degrees Fahrenheit for short periods of time, according to Harley. But the combined effects of peak heat of the day coinciding with the afternoon’s low tide were too much for the mussels to muscle through.

"A mussel on the shore in some ways is like a toddler left in a car on a hot day," Harley says to CBC. “They are stuck there until the parent comes back, or in this case, the tide comes back in, and there's very little they can do. They're at the mercy of the environment.”

The devastation of shellfish such as mussels, oysters and clams can have dire impacts on the ecosystem. They filter seawater and keep the water clean. They’re also important food sources to larger animals such as seabirds.

Shellfish are vital to the economy in the region, and shellfish farmers have made similar observations of the heat wave ravaging their livestock. Hama Hama Oyster Company, a fifth-generation, family-run shellfish farm in Washington State’s Olympic Peninsula, recorded scores of cooked clams on the muddy banks of the Salish Sea, reports Molly Taft for Gizmodo. With grisly humor, the company noted in an Instagram post that the heat wave was “clamitous" to their business, per the Post.

“These ‘once in a hundred year’ weather events are really coming at us pretty quickly, one after another, which is getting pretty exhausting,” Lissa James Monberg of Hama Hama Oysters tells the Post.

Although this heat wave has been described by experts as “quite extraordinary,” the sad truth is that these heat-induced, large-scale die-offs aren’t quite so out-of-the-blue, reports CBC. Sea star populations all along the North American west coast have plummeted over the years, due to a mysterious disease egged on by overheating oceans, per Gizmodo.

Australia’s Great Barrier Reef has lost half of its coral since 1995, bleached to death by the irresistible warming of the ocean. Even northern California’s coast experienced a similar mussel cookout in their own separate heat wave in June, reports Amy Graff of SFGate. Experts have long predicted such an event like last June’s mass marine mortality, reports CBC, and warn that extreme heatwaves could occur with higher frequency in the future. But nature is resilient; the mussel bed might recover in a year or two, Harley says.

He hopes June’s tragedy will encourage people to take action against climate change.

"We need to work harder to reduce emissions and take other measures to reduce the effects of climate change," Harley tells CBC.

About Shi En Kim
Shi En Kim

Shi En Kim is a writer and researcher at the University of Chicago who studies the physics of nano-sized objects. Outside the lab, she freelances for various publications, including National Geographic, Scientific American, Science News, Slate and others. She is Smithsonian's 2021 AAAS Mass Media Fellow. Follow her on Twitter at @goes_by_kim.

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