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Ward, James W.; Warden, John G.; Bandy, Ashley M.; Fryar, Alan E.; Brion, Gail M.; Macko, Stephen A.; Romanek, Christopher S.; Coyne, Mark S.

Use of Nitrogen‐15‐Enriched Escherichia coli as a Bacterial Tracer in Karst Aquifers

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  • Medientyp: E-Artikel
  • Titel: Use of Nitrogen‐15‐Enriched Escherichia coli as a Bacterial Tracer in Karst Aquifers
  • Beteiligte: Ward, James W.; Warden, John G.; Bandy, Ashley M.; Fryar, Alan E.; Brion, Gail M.; Macko, Stephen A.; Romanek, Christopher S.; Coyne, Mark S.
  • Erschienen: Wiley, 2016
  • Erschienen in: Groundwater
  • Sprache: Englisch
  • DOI: 10.1111/gwat.12426
  • ISSN: 0017-467X; 1745-6584
  • Entstehung:
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  • Beschreibung: <jats:title>Abstract</jats:title><jats:p>Karst aquifers are susceptible to contamination by microorganisms, but relatively few studies have used bacteria as tracers. We demonstrate the utility of <jats:italic>Escherichia coli</jats:italic> enriched in the stable isotope nitrogen‐15 (<jats:styled-content style="fixed-case"><jats:sup>15</jats:sup>N</jats:styled-content>) as a novel bacterial tracer. Nonpathogenic <jats:italic>E. coli</jats:italic> from two springs in central Kentucky were grown on <jats:styled-content style="fixed-case"><jats:sup>15</jats:sup>N</jats:styled-content>‐enriched media. Survival of <jats:italic>E. coli</jats:italic> and persistence of the isotopic signal were assessed in two sets of laboratory experiments conducted with sterilized spring water in dark microcosms at 14 °C. First, isotopically labeled bacteria survived for 130 d at concentrations within one log unit of the average initial value, and there was no significant difference in <jats:styled-content style="fixed-case">δ<jats:sup>15</jats:sup>N</jats:styled-content> values from Day 1 to Day 130. Second, water samples with <jats:italic>E. coli</jats:italic> were inoculated with either of two different species of protozoa (<jats:italic>Tetrahymena pyriformis</jats:italic> or <jats:italic>Colpoda steinii</jats:italic>). During 7 d, <jats:styled-content style="fixed-case">δ<jats:sup>15</jats:sup>N</jats:styled-content> values increased in <jats:italic>T. pyriformis</jats:italic> while bacterial populations decreased. In a field test, following a 2.1‐cm rainfall, <jats:styled-content style="fixed-case"><jats:sup>15</jats:sup>N</jats:styled-content>‐labeled <jats:italic>E. coli</jats:italic>, solutes (rhodamine <jats:styled-content style="fixed-case">WT</jats:styled-content> dye and bromide), and latex microspheres were injected into a sinkhole approximately 530 m upgradient of a spring. Breakthrough of all tracers coincided, but microspheres were remobilized by subsequent storms, unlike other tracers. Enriched <jats:italic>E. coli</jats:italic> exhibited more tailing than solute tracers during the initial storm‐flow recession. These results indicate that <jats:styled-content style="fixed-case"><jats:sup>15</jats:sup>N</jats:styled-content>‐enriched <jats:italic>E. coli</jats:italic> is a viable tracer of bacterial transport in karst aquifers, although predation may attenuate the isotopic signal in systems that are not rapidly flushed.</jats:p>