Skip to main content
ARS Home » Research » Publications at this Location » Publication #338425
Title: Use of molecular markers to compare Escherichia coli transport to traditional groundwater tracers in epikarst

Author
item BANDY, ASHLEY - University Of Kentucky
item Cook, Kimberly - Kim
item FRYAR, ALAN - University Of Georgia
item POLK, JASON - Western Kentucky University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2017
Publication Date: 1/12/2018
Citation: Bandy, A., Cook, K.L., Fryar, A., Polk, J. 2018. Use of molecular markers to compare Escherichia coli transport to traditional groundwater tracers in epikarst. Journal of Environmental Quality. 47:88-95. doi:10.2134/jeq2017.10.0406.

Interpretive Summary: Bacterial contamination of karst aquifers is a concern as water quality across the globe deteriorates in the face of decreasing water security. Traditional groundwater tracers (dye and microspheres) do not exhibit surface properties similar to bacteria and pathogens and therefore are not good proxies for risk assessment involving transport of microorganisms within these water resources. This study examined the transport and attenuation of two non-virulent isolates of Escherichia coli (E. coli) in relation to traditional groundwater tracers (rhodamine WT dye and latex microspheres) through epikarst in western Kentucky. Molecular biology techniques were successful in detecting bacteria that were transported approximately 30 m through epikarst above a cave. Differential movement between the four tracers was observed, with differences in behavior dependent on flow conditions. Dye arrived at the sampling site prior to particulates. Attenuation was greater for the bacterial isolate containing genes known to promote adherence to surfaces than for the isolate with genes responsible for capsular formation. Microspheres of comparable size (1 µm diameter) were first detected simultaneously with the isolate that did not attach to surfaces as well, but peaked in concentration during increases in discharge > 11 d post-injection. Bacteria were remobilized during storm events over 2 months after injection, illustrating the storage capacity of epikarst with regard to potential contaminants.

Technical Abstract: Bacterial contamination of karst aquifers is a concern as water quality across the globe deteriorates in the face of decreasing water security. Traditional groundwater tracers (dye and microspheres) do not exhibit surface properties similar to bacteria and pathogens and therefore are not good proxies for risk assessment involving transport of microorganisms within these water resources. This study examined the transport and attenuation of two non-virulent isolates of Escherichia coli (E. coli) in relation to traditional groundwater tracers (rhodamine WT dye and latex microspheres) through epikarst in western Kentucky. Molecular biology techniques were successful in detecting bacteria that were transported approximately 30 m through epikarst above a cave. Differential movement between the four tracers was observed, with differences in behavior dependent on flow conditions. Dye arrived at the sampling site prior to particulates. Attenuation was greater for the bacterial isolate containing the iha gene, compared to the isolate containing the kps gene. Microspheres of comparable size (1 µm diameter) were first detected simultaneously with the kps isolate, but peaked in concentration during increases in discharge > 11 d post-injection. Bacteria were remobilized during storm events over 2 months after injection, illustrating the storage capacity of epikarst with regard to potential contaminants.