Composite analysis for Escherichia coli at coastal beaches
Journal of Great Lakes Research
By: E.E. Bertke
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Abstract
At some coastal beaches, concentrations of fecal-indicator bacteria can differ substantially between multiple points at the same beach at the same time. Because of this spatial variability, the recreational water quality at beaches is sometimes determined by stratifying a beach into several areas and collecting a sample from each area to analyze for the concentration of fecal-indicator bacteria. The average concentration of bacteria from those points is often used to compare to the recreational standard for advisory postings. Alternatively, if funds are limited, a single sample is collected to represent the beach. Compositing the samples collected from each section of the beach may yield equally accurate data as averaging concentrations from multiple points, at a reduced cost. In the study described herein, water samples were collected at multiple points from three Lake Erie beaches and analyzed for Escherichia coli on modified mTEC agar (EPA Method 1603). From the multiple-point samples, a composite sample (n = 116) was formed at each beach by combining equal aliquots of well-mixed water from each point. Results from this study indicate that E. coli concentrations from the arithmetic average of multiple-point samples and from composited samples are not significantly different (t = 1.59, p = 0.1139) and yield similar measures of recreational water quality; additionally, composite samples could result in a significant cost savings.
Suggested Citation
Bertke, E., 2007, Composite analysis for Escherichia coli at coastal beaches: Journal of Great Lakes Research, v. 33, no. 2, p. 335-341, https://doi.org/10.3394/0380-1330(2007)33[335:CAFECA]2.0.CO;2.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Composite analysis for Escherichia coli at coastal beaches |
| Series title | Journal of Great Lakes Research |
| DOI | 10.3394/0380-1330(2007)33[335:CAFECA]2.0.CO;2 |
| Volume | 33 |
| Issue | 2 |
| Year Published | 2007 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Great Lakes Research |
| First page | 335 |
| Last page | 341 |