In a series of field and watershed scale studies, the genetic diversity of Escherichia coli in
secondary habitats (e.g. soils and sediments) of an agricultural watershed was assessed in
order to examine the dynamics of E. coli inhabiting these matrices and to determine their
contribution to waterborne populations. Using replicated field plots, persistent
subpopulations of E. coli were observed to be significantly affected by hillslope position
due to inherent differences in soil texture and moisture content. The dynamics of E. coli
populating tile drainage effluent in a working cultivated field were monitored and it was
observed that putatively naturalized E. coli dominated the effluent after approximately 55
days following manure amendments. The contribution of tile drainage effluents to the
waterborne E. coli population in an adjacent stream was exponentially related to tile
discharge rates, regardless of whether the effluent was populated by manure-associated or
naturalized E. coli strains. Streambed E. coli populations differed according to stream
geomorphological features, with strains responding to sediment texture and water
velocity distributions among the features. In a temporal study of sediment E. coli,
population turnover was observed to be affected by sediment redistribution in highenergy
stream reaches and was stabilized by immigration from adjacent catchment
sources in low-energy stream reaches. Reach-specific connectivity between sediment and
waterborne E. coli populations was observed in this watershed. Reach- and catchmentscale
hyporheic processes are speculated to be occurring, which may be in part influenced
by strain-dependent attachment behaviour of E. coli strains in disjoint stream reaches
influenced by different catchment sources of E. coli. The attachment of waterborne E.
coli to suspended particles was observed to be associated with land use, water quality and
suspended particle variables. The relationship of land use type to particle attachment
reinforces the hypothesis that strain-specificity in attachment behaviour can affect the
transport of E. coli in fluvial systems. This work provides evidence that putatively
naturalized strains in cultivated fields can contribute a large part to waterborne E. coli,
and that reach-specific hydrological factors need to be considered when relating
sediment- to waterborne E. coli in fluvial systems.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/42802 |
| Date | 29 November 2013 |
| Creators | Piorkowski, Gregory Stuart |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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