TITLE:
Homogeneous Distribution of Escherichia coli Measured within the Vertical Water Column of Small, Freshwater Streams
AUTHORS:
David. W. Buckalew, Albert. J. Tuono, Amanda. K. Simmons, Travis. W. Lankford, Donald. H. Smith
KEYWORDS:
Indicator Bacteria, Stratification, Water Monitoring, E. coli
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.7 No.5,
March
26,
2015
ABSTRACT: Sampling
for coliform bacterial indicators such as Escherichia
coli (E. coli) provides a
universally accepted gauge of the microbiologic quality of fresh surface waters
worldwide. Protocols for the capture, preservation, and analysis of indicator
bacteria collected from moving waters (e.g., rivers, streams, canals, etc.)
parallel those for collecting bacteria from standing waters (e.g., ponds,
lakes, and impoundments). Strict depth- and width-integrated rules established
for testing moving waters are likely a result of the historical precedence of
our knowledge of bacterial stratification in standing waters. Sampling
protocols for indicator bacteria in freshwater streams recommend capture and
retrieval of samples from the mid-water column directed into the current and
within the deepest portion of the channel to prevent collection of either
benthic particles or surface films. Chi-square analyses of multiple stratified
samples captured on the same date and time reveal that variability in sampling
position at specified depths within the main stream column or within randomly
chosen locations within the main stream channel has no effect (p ≥ 0.25) upon
such indicator bacteria numbers. Additionally, these data are the first to show
that concentrations of the common bacterial indicator, E. coli, are homogeneously distributed throughout both lateral area
and vertical water column within/near a single sampling location of a moving
water body up to 245 cubic feet per second (cfs) discharge. Moreover, one data
point (bacterial sample) appears to represent the overall bacterial
concentration of a small freshwater stream obtained from any single sampling
location within/near the main channel for a given date and time. These findings
suggest some latitude in sampling strategies for assessing small freshwater
streams for indicator bacteria such as E.
coli for workers in both environmental and public health fields.