Agriculture fingered as E. coli source in Lake Huron study

Thursday, May 7, 2009

© AgMedia Inc.
by MIKE MULHERN & BETTER FARMING STAFF

Just in time for the summer cottage - and farming -season, a new study has re-ignited a long standing controversy into the role agriculture plays in polluting Lake Huron beaches.

The study, funded by provincial and federal governments and conducted by researchers at the University of Guelph and the Ontario Ministry of the Environment in 2005 and 2006, found livestock and poultry manure accounts for roughly two thirds of E. coli measured in the rural watershed of Eighteen Mile River. The small stream meanders across the border between Huron and Bruce Counties. Samples were also taken at nearby Ashfield Township Park beach.

Researchers compared their water and beach samples to a DNA library constructed from samples collected from manure storages, septic tanks and wildlife in the area.

John Fitzgibbon, chair of the steering committee of the Ontario Farm Environmental Coalition, and director of the School of Rural Planning and Development at University of Guelph, commended the study. "I think it is an excellent idea. We need more of them."
 
Fitzgibbon asserts that a single study of a small rural watershed where few humans live is not the basis to develop policy that would be used to rip agriculture. He says the study doesn’t show that “big barns” are to blame for E. coli in streams and on the beach.

"If you take one study and develop policy you have to be a bit of a damn fool," Fitzgibbon says.

While manure was the top source of  E. coli found in the study, an "environmentally adapted" strain also turned up on the shoreline. University of Guelph microbiologist Jack Trevors, who conducted the research, says that strain’s importance can’t be underestimated because no one knows how long those bacteria persist. “It could be days, weeks, months,” he says.

Trevors says researchers don’t know how much of the bacteria came from cows as opposed to pigs because a breakdown by species would have been too expensive.
 
He did say an estimate of the “total fecal material within the Eighteen Mile River watershed” from the 2001 census predicted 66 per cent would come from cows, 24 per cent from pigs, seven per cent from poultry, two per cent from sheep and horses and one per cent from humans.

The 2005-2006 DNA study allowed the researchers to break the numbers down based on samples taken from lake stations, lake surveys and the river. They found, on average, about 60.2 per cent of E. coli came from agriculture, 9.9 per cent from wildlife, about 2.5 per cent from humans, 17.5 per cent from the adapted strain and about 9.7 per cent from unknown sources.

Fitzgibbon describes the library of known source bacteria to compare against samples found in the stream and lake water as "good. . . . but a little thin."

He says the study's authors point out the source of nearly 10 per cent of E. coli can't be accurately determined. Physiologically, the guts of humans and pigs are nearly the same, Fitzgibbon says.

Clarification: The study was financed by the Best in Science Program of the Ontario Ministry of the Environment.

E. coli bacteria are a sign of fecal contamination, Fitzgibbon says, and for the most part don't cause disease. E. coli 0157:H7, blamed for illness and death in Walkerton in 2000 is one type.
 
Fitzgibbon isn't surprised there is more bacteria there from livestock than from human sewage because of the low population. In fact, he's surprised there was human-source bacteria at all. "It's supposed to be treated," he points out.
 
Eighteen Mile River has its source near Holyrood in Huron-Kinloss Township and cuts across a corner of Ashfield-Colborne-Wawanosh Township  before emptying into Lake Huron south of Amberley.

The study was published in the March issue of the Canadian Journal of Microbiology, published  by the National Research Council Canada.  BF