Resuspension of Sediment‐Associated Escherichia coli in a Natural Stream

Abstract

In this study, a tracer bacteria was used to investigate the resuspension and persistence of sediment-associated bacteria in a small alluvial stream. The study was conducted in Swan Creek, located within the Grand River watershed of Ontario, Canada. A 1.1-m2 section of the bed was seeded with a strain of Escherichia coli resistant to nalidixic acid (E. coli NAR). The survival, transport, and redistribution of the tracer bacteria within a 1.7-km river section downstream of the source cell was assessed for a 2-mo period following the introduction of the tracer bacteria. This study has illustrated that enteric bacteria can survive in bed sediments for up 6 wk and that inactivation of the tracer bacteria resembled typical first-order decay. Critical conditions for resuspension, as well as resuspension rates, of sediment-associated bacteria were determined for several storm events. The critical shear stress for E. coli NAR resuspension in Swan Creek ranged from 1.5 to 1.7 N m(-2), which is comparable with literature values for critical shear stresses for erosion of cohesive sediments. Bacteria resuspension was primarily limited to the rising limb of storm hydrographs implying that a finite supply of sediment-associated bacteria are available for resuspension during individual storm events. The information presented in this paper will further the development of representative microbial water quality models.

Intermittent riverine resuspension: Effects on phosphorus transformations and heterotrophic bacteria

“…Hydrodynamics of the benthic water column simulatorIn many field studies, resuspension was initiated by creating artificial flooding events or by mechanically agitating (raking) bed sediments (Nagels et al 2002;Jamieson et al 2005) and in lab studies by horizontal shaking (Stå hlberg et al 2006;Li and Huang 2010). The applicability of such approaches is questionable since either natural hydrodynamics and/or resuspension-associated concomitant benthic nutrient supply to the bacterial community are not appropriately simulated.…”

“…The variable time lags between increase in nutrient availability and bacterial multiplication can explain why none of the regressions were significant. Jamieson et al (2005) reported values for E of colony forming units (CFU) E CFU for an alluvial stream sediment (loss on ignition 5 8% dry wt), Swan Creek, southern Ontario, Canada. During storm events, E CFU varied between 39.6 3 10 6 CFU m 22 h 21 at t b 5 1.7 N m 22 (u* , 4.12 cm s 21 ) and 54 3 10 6 CFU m 22 h 21 at t b 5 1.5 N m 22 (u* , 3.87 cm s 21 ).…”

“…Since resuspension events cause subsequent aggravation of in-stream water quality, a number of field (Nagels et al 2002;Jamieson et al 2005) and laboratory studies (Pusceddu et al 2005;Stå hlberg et al 2006) have been performed, while only a few ecosystem modeling efforts have addressed this issue (Bai and Lung 2005;Rehmann and Soupir 2009).…”

“…Moreover, current standard water quality models do not include resuspension as a source of microbes (Rehmann and Soupir 2009), or the latter are restricted in their physical representation by their association with the sediment. Most water quality models treat bacteria as freefloating colloids with neutral buoyancy despite the general consensus that bacteria are often associated with resuspended particles (Grossart et al 2004;Jamieson et al 2005).…”

Numerical Modelling Sediment-Bacteria Interaction Processes in the Severn Estuary

“…This transport can have a major effect on the quality of bathing waters. Jamieson et al [4] conducted field experiments in Swan Creek, Canada, by using the bacteria tracer E. coli NAR in their studies. They found that the reappearance of the bacteria tracer in the water column coincided with increases in the total suspended solids load, which indicated that the E.coli NAR were being re-suspended with the sediment load.…”