Ask the Clams

500-year-old quahog clams can tell us a few things about our changing oceans.
John Thompson

WWU Research Assistant Professor of Marine and Coastal Sciences Nina Whitney has enlisted an unlikely ally in the effort to better understand rising ocean temperatures: the ocean quahog (pronounced “kow-haag”), an East Coast distant relative of the Pacific Northwest’s geoduck clam.

Ocean quahogs have a long story to tell; they hold the record for longest-lived, non-colonial species on the planet, with life spans that can eclipse 500 years, and getting them to divulge their secrets can unleash a trove of data.

“These clams are what we call an ‘environmental proxy,’” Whitney says. “Quahogs precipitate a layer of shell each year the same way a tree grows a ring, and we can pull data from each ring. And when you see how long each of them can live, that is a lot of environmental data hidden in the shell of one clam.”

Pulling that data uses a scientific technique called sclerochronology, the study of physical and chemical variations in the accretionary hard tissues of organisms, and the context in which they formed.

“Sclerochronology allows us to reconstruct changes in the environment that each of the clams experienced while it was alive,” Whitney says. “And using shells from collections we can piece together a pretty good record.”

Whitney has been working with quahogs on this project for more than nine years, from her time as a master’s student through getting her doctorate and then working as a postdoctoral researcher at Woods Hole Oceanographic Institution on Cape Cod. A native Mainer who grew up on the coast, trying to better understand the changes that the Gulf of Maine is going through was a natural fit for her research interests.

“I just thought it was fascinating, that we could use information hidden in a clamshell to tell us all about the ocean currents, ocean circulation changes, water temperature and more, all from the isotope chemistry and radiocarbon signatures that each clam has,” she says. “And the waters off Maine were a perfect subject, because so many people in my home state rely on that water for their livelihoods.”

Whitney says the goal of her research, which was published last August in the scientific journal Communications Earth and Environment, showed that warming in the Gulf of Maine in the 20th century reversed in 100 years the long-term cooling that has been occurring over the previous 1,000 years.

“Yeah, it didn’t take nearly as long to heat up as it did to cool down,” Whitney says. “The warming trends corresponded with a change in ocean circulation that also brought more water from the warm Gulf Stream into the Gulf of Maine, and less from the colder Labrador Current.”

And what do climate models point to as the cause for the changes in ocean circulation and temperature in this region? While everything from volcanoes to solar activity have some input, she says, the main culprit is a familiar one: greenhouse gases.

After growing up in Maine and getting her doctorate at Woods Hole Oceanographic Institution on Cape Cod, Whitney just celebrated her first anniversary at Western. Now that she’s a Pacific Northwesterner, might there be some geoduck research in her near future?

“We’ll have to see,” she says with a laugh. “Not all clams can tell the same story.”

is Western’s assistant director of Communications.