Ann. Limnol. - Int. J. Lim.
Volume 47, Number 1, 2011
|Page(s)||11 - 19|
|Published online||24 December 2010|
Variation of an indicator of Escherichia coli persistence from surface waters of mixed-use watersheds, and relationship with environmental factors
1 Agriculture and Agri-Food Canada, 1391 Sandford St, London, ON N5V 4T3, Canada
2 Agriculture and Agri-Food Canada, 960 Carling Ave, Ottawa, ON K1A 0C6, Canada
3 Agriculture and Agri-Food Canada, 5403 1st Ave S, Lethbridge, AB T1J 4B1, Canada
4 Agriculture and Agri-Food Canada, 2560 boul. Hochelaga, Sainte-Foy, QC G1V 2J3, Canada
5 Institute for Resources, Environment and Sustainability, University of British Columbia, 429-2202 Main Mall, Vancouver, BC V6T 1Z4, Canada
6 Alberta Environment, 2938-11 St. NE, Calgary, AB T2E 7L7, Canada
7 Environment Canada, 867 Lakeshore Road, Burlington, ON L7R 4A6, Canada
* Corresponding author: Ed.Topp@agr.gc.ca
Accepted: 31 October 2010
Escherichia coli is an indicator of fecal pollution used to mandate recreational and drinking water quality. Concentrations of culturable E. coli following contamination of surface water are determined by three factors: dilution; cell attachment to particulate material and settling or resuspension in the water column; and the net rate of change in viability. This study evaluated the variability in the latter parameter, and how predictive variation in death rate was of culturable population densities at the time of sampling. Water samples (N=232) with varying levels of E. coli contamination were collected from 46 discrete locations in four watersheds across Canada over a three-month period and enumerated for culturable E. coli by membrane filtration plate counting (T0EC). Water samples were again enumerated following a laboratory 24 h holding period at 30°C in the dark, and the difference considered the death rate (ΔEC). Relationships of T0EC and ΔEC with environmental and water chemistry factors were explored using step-wise multiple regression. The model predicting T0EC indicated that stream order, total rainfall seven days in advance of sampling day, total phosphorus, and ΔEC were the most significant contributors. The model predicting ΔEC indicated that turbidity and NH3+NH4 were the most important contributors. A model suggests that the persistence factor is less important than dilution (i.e. stream order) in describing E. coli densities, followed by factors that influence the loading of E. coli into watersheds.
Key words: Escherichia coli / surface water / persistence / environmental factors
© EDP Sciences, 2010
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