Heat Dome Die-Off

Dr. Henry Choong Examines the Loss of Intertidal Filter Feeders in BC

Oysters, mussels and clams are known for their resilience—they can survive extreme changes in moisture, temperature and salinity and withstand strong waves. But this summer they died by the hundreds of millions as BC’s “heat dome” shattered hightemperature records across the province and wreaked havoc on intertidal ecosystems.

Dr. Henry Choong collecting mussels at Calvert Island, Hakai Protected Area, 2017.

By Wesley Macinnis Communications Specialist

Calvert Island, Hakai Protected Area

“Scientists estimate that more than one billion marine animals along BC’s coastline may have perished because of the unprecedented heatwave” says Dr. Henry Choong, curator of invertebrate biology at the Royal BC Museum. “Intertidal invertebrates such as oysters, mussels and clams have to be very resilient to survive in what is already a harsh environment, so it’s concerning to see conditions that cause them to perish in such great numbers.”

The availability of climate data limits how far back we can look for precedents to the heat dome, but one study found that the frequency, duration and intensity of heatwaves all increased globally between 1950 and 2000, and concluded that this trend would only accelerate with global warming, causing more severe and possibly irreversible impacts.

Shellfish and crustaceans, the animals that bore the brunt of the impact during BC’s heatwave, don’t usually make frontpage news—at least, not nearly as often as BC megafauna such as caribou, grizzlies and whales—but it’s worth considering what could happen to BC’s coast if we continue to lose intertidal invertebrates on a large scale.

“They filter the water for us,” says Henry. “When filter feeders die in such large numbers, water quality will be compromised, and that will affect other marine life as well.”

Oysters, mussels and clams are filter feeders. They strain large quantities of water for microscopic plants and animals, removing excess nitrogen from the water as they feed. Without this process, excess nitrogen in the water can cause algae blooms that can overwhelm, toxify and ultimately suffocate marine ecosystems.

Because of these organisms’ ability to remove excess nitrogen from the water, many coastal municipalities and aquaculture businesses across North America already use filter feeders to complement wastewater treatment practices.

“Since it is likely that impacts on the intertidal zone could increase with global warming, we can all do our part to help minimize the damage caused by global warming, such as making energy-efficient decisions and being mindful of our interactions with the environment,” says Henry.

Museums and museum professionals also have an important role to play.

“Museum collections, such as the Royal BC Museum natural history collections, provide a unique and critical window to the past, present and future by maintaining a specimen-based record of biodiversity data,” says Dr. Choong. “Our collection-based research helps us to explore questions related to the impact of climate change on species in BC and elsewhere.” In short, because our collections contain records made over more than a century, we can compare past and present conditions with ease—an essential tool in investigating the effects of climate change.

To learn more about Dr. Henry Choong’s work and the museum’s natural history collections, visit rbcm.ca/staff.