|
A UVic graduate student tracks the source of bacterial contamination in watersheds
by Valerie Shore
It's hard not to laugh when Cindy Meays tells you how she spent an entire summer working with cow patties—collecting them, blending them, reshaping them and, finally, analysing them.
"The students working with me thought I was a little crazy at first," grins the University of Victoria graduate student. "My friends call me ‘Dr. Poo.'"
The joke possibilities seem limitless, but Meays's research is really no laughing matter. For her PhD degree in biology, she has completed a landmark study on the bacterial contamination of drinking water in watersheds.
Many Canadians draw their drinking water from watersheds that are exposed to various land uses, such as agriculture, forestry, mining, urban development and recreation. These activities sigificantly increase the risk of contaminated drinking water and disease.
As a result, hundreds of communities endure boil-water advisories every year. In B.C. alone, an estimated 300-400 communities are on boil-water advisories at any given time.
"Microbial contamination of source water is a major environmental and health issue with drinking water in B.C., Canada and around the world," says Dr. Asit Mazumder, a UVic aquatic ecologist and Meays's thesis co-supervisor. "Unless we know the source of contamination, we can't control it. Cindy's work is a big step in that direction."
Working near Vernon, B.C., Meays began her study with the cow patties in what is more formally known as a fecal pat experiment. The object of her interest was the bacterium Escherichia coli, which occurs naturally in the intestinal tract of most warm-blooded animals, including humans.
"The presence of E. coli in water indicates that fecal contamination has occurred, so we typically measure it to see what the concentrations are," says Meays. Most strains of E. coli are harmless, even beneficial, but some can be deadly. It was a waterborne strain of E. coli that killed seven people in Walkerton, Ontario, in 2000.
"It's important if we're looking at watershed management to have some idea how long E. coli can live," says Meays. So she placed 200 kg of collected, blended and reassembled cow patties into a variety of controlled conditions and measured E. coli survival rates.
In general, shady, moist and cool are optimal for survival, although Meays was surprised at the bacterium's resilience. "By the end of 45 days the patties were very dry and you wouldn't expect any E. coli to be alive. But some were."
In the second phase of her study, Meays field-tested a new genetic technique for tracking the source of E. coli in a watershed. Known as molecular fingerprinting, or "ribotyping," it identifies the bacterium's host organism—livestock, wildlife or human—from an analysis of DNA fragments.
Meays's study—so far the largest of its kind in the world—analysed more than 4,800 E. coli samples taken from four watersheds in the Vernon area over different time scales, and matched them to collected scat samples. She also tracked whether concentrations and sources of E. coli changed over time.
She found that numbers vary, depending on such factors as location, season, elevation, weather and time of day. "This shows managers that monitoring water quality by taking occasional samples won't necessarily represent what's going on in a particular stream," says Meays.
Meanwhile, the ribotyping revealed a wide assortment of animals contributing to E. coli contamination —depending on the watershed, every-thing from birds, deer and rodents, to cattle, horses and domestic dogs. This is a powerful management tool, says Meays.
"It gives us a much better understanding of what's going on in a watershed so that stakeholders aren't just pointing fingers at each other," says Meays. "Instead, they can alter their activities to reduce the contamination risk."
Funders and supporters of the project included Agriculture and Agri-Food Canada, the B.C. Beef Cattle Industry Development Fund, the North Okanagan Livestock Association, the Agricultural Environment Partnership Initiative, the Natural Sciences and Engineering Research Council, the Canadian Institutes of Health Research, three B.C. ministries (Agriculture and Lands, Environment, and Forests and Range) and UVic.
|
