Christensen conducting field work with Larry Jorgenson, member of the Heltsiuk First Nations and owner of Koeye River Lodge.
BC grizzlies carry worrisome levels of manmade toxins, grad student finds
By Valerie Shore
We’ve all seen them—photos of grizzly bears snatching salmon from raging waterfalls or grazing on sedge grass in picturesque estuaries. They symbolize a wilderness world far removed from the hustle and bustle of modern urban life.
But is our wilderness as pristine as we think it is?
No it isn’t, says Jennie Christensen, who has just completed a four-year study of environmental contaminants in BC grizzlies. She graduated last month with a PhD from UVic’s School of Earth and Ocean Sciences.
“I’ve always felt a strong connection with wildlife and the environment,” says Christensen, who was born in Courtenay but spent most of her childhood in St. Albert, AB. Her first introduction to the world of grizzlies came during a high school work experience program.
Grizzly. Photo: Valerie Shore
“I was lucky enough to hold and feed two orphaned cubs—it was amazing. How could I resist an opportunity to work with these animals in the future?”
That opportunity presented itself after Christensen had completed her master’s in amphibian toxicology. She saw an ad for the PhD project—a partnership with Fisheries and Oceans Canada, the Raincoast Conservation Society and UVic—and jumped at the chance.
“Recent studies show that salmon can contain a number of contaminants originating from all over the globe,” she explains. These pollutants include PCBs, DDT, other organochlorine pesticides, and flame retardants known as PBDEs.
“We wanted to find out whether salmon are playing a role in delivering these contaminants to grizzlies.”
The answers have important implications not just for the bears and the ecosystems in which they live, but for human health, as governments seek effective ways to regulate the use and spread of these highly toxic chemicals.
PCBs and DDT are linked with immune, reproductive and brain impairments and are largely banned in North America. But they’re still used in developing nations and are transported globally by air and through the food chain.
So are PBDEs, which are still legally and widely used by Canadian and US manufacturers in everyday products such as televisions, computers, furniture and clothing. When these items are discarded into the environment, PBDEs creep their way up the food chain, concentrating as they go.
To find out what toxic load BC grizzlies are carrying, hair and fecal samples were collected from bears in coastal and interior regions of BC. Fat samples were taken from legally hunted bears. Christensen also spent many hours on the Koeye River on the central coast, observing feeding bears and collecting food items.
“This dietary information is critical if we are to understand how different foods transfer contaminants to the bears,” says Christensen, who is respectful but fond of the powerful bruins. One Koeye bear, a young male she and her team named Zoolander, was especially endearing.
“Every day, for hours, he would follow us as we worked. When we stopped to collect food samples, he would stop too and lay down and have a snooze.”
In general, the study found that bears that consume salmon contain higher concentrations of DDT and PCBs than interior bears, which eat mainly vegetation. But the interior bears harbour “significantly higher” concentrations of PBDEs. This was a surprise to Christensen.
“We expected the salmon-eating bears to be more contaminated with PBDEs,” she says. “This clearly demonstrates that local use of PBDEs is having an impact on wildlife in the terrestrial food web.”
A unique risk factor for bears is hibernation, when they burn their fat stores for energy. “In some cases, the contaminants are tripling in concentration by the time the bears emerge in spring,” says Christensen. “Hibernation is also when mothers give birth and nurse their young, so vulnerable cubs are being exposed to the highest concentrations through their mother’s milk.”
While contaminant levels overall were lower than those in other animals where toxic effects have been observed, there is still cause for concern, says Christensen. “Some toxic effects can occur at the sub-cellular level, and research is only beginning to uncover the health ramifications at this scale.”
Although the study is completed, Christensen says that grizzlies, coastal rainforests and toxicology will always be an important part of her personal and professional life.
“Our coastal rainforests are incredible and are something we should be really proud of,” she says. “However, these forests and all the wildlife that depend upon them desperately need our protection and increased conservation efforts.”
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