Fecal indicator bacteria concentrations, a measure of water pollution, do not remain static in the environment and can fluctuate both temporally and spatially. Diurnal variation, partially resulting from the effects of UV light, may decrease the density of E. coli, resulting in lower concentrations in the afternoon. Previous studies conducted at 63rd Street Beach in Chicago, IL [1] and North Beach in Racine, WI [2] demonstrated significant diurnal variation using an E. coli standard and culture-based assays. Subsequent studies conducted at sewage-impacted Great Lakes beaches employing molecular assays (qPCR) found that the signal remained stable; it is unknown whether a similar scenario exists at non-sewage impacted beaches. During the summer of 2011, surface water samples were collected in the morning and afternoon (0700 and 1200) and analyzed by both IDEXX/Colilert and qPCR/BioGx SmartBeads/OmniMix HS to determine if temporal variation in E. coli was occurring (n = 29/23, culture/qPCR). Analysis of log-converted data (independent t-test/one-way ANOVA) indicated no significant difference in mean E. coli concentration as determined by morning and afternoon sampling via either method (Colilert/qPCR, p = 0.49/0.09, α = 0.05). Although not statistically significant (p = 0.09) there were 5 of 23 (22%) instances where afternoon qPCR values exceeded morning counterparts; two (10%) when culture-based assays did not show a similar response. The utility of rapid assays lies in their ability to generate results prior to beach opening; temporal or event-based fluctuations should be considered when using molecular assays at non-sewage impacted beaches for regulatory purposes.
R. Whitman and M. Nevers, “Escherichia coli Sampling Reliability at a Frequently Closed Chicago Beach: Moni- toring and Management Implications,” Environmental Science & Technology, Vol. 38, No. 16, 2004, pp. 4241- 4246. doi:10.1021/es034978i
J. Kinzelman, “Investigating Bathing Water Quality Failures and Initiating Remediation for the Protection of Public Health,” Ph.D. Dissertation, University of Surrey, Guildford, 2005.
National Technical Advisory Committee (NTAC), “Water Quality Criteria, Washington, DC,” Federal Water Pollution Control Administration, 1968.
United States Environmental Protection Agency (US EPA), “Clean Water Act,” United States Environmental Protection Agency, Washington DC, 1977.
US EPA, “Ambient Water Quality Criteria for Bacteria, Office of Water Regulation and Standards, Criteria and Standards Division,” United States Environmental Protection Agency, Washington DC, 1986.
US EPA, “Beaches Environmental Assessment and Coastal Health (BEACH) Act of 2000,” United States Environmental Protection Agency, Washington, DC, 2000.
National Resources Defense Council (NRDC), “Testing the Waters: A Guide to Water Quality at Vacation Beaches,” 2011.http://www.nrdc.org/water/oceans/ttw/titinx.asp
R. Haugland, S. Siefring, L. Wymer, K. Brenner and A. Dufour, “Comparison of Enterococcus Measurements in Freshwater at Two Recreational Beaches by Quantitative Polymerase Chain Reaction and Membrane Culture Analysis,” Water Research, Vol. 39, 2005, pp. 559-568. doi:10.1016/j.watres.2004.11.011
United States House of Representatives, “H.R. 2537, Beach Protection Act of 2007,” 110th United States Con- gress, Washington DC, 2007, pp. 1-20. http://www.gpo.gov/fdsys/pkg/CRPT-110hrpt491/pdf/CRPT-110hrpt491.pdf
United States House of Representatives, “H.R. 2093, Clean Coastal Environment and Public Health Act of 2009,” 111th United States Congress, Washington DC, 2009, pp. 1-16. http://www.gpo.gov/fdsys/pkg/BILLS-111hr2093rh/pdf/BILLS-111hr2093rh.pdf
J. Griffith, D. Moore, C. McGee and S. Weisberg, “Technical Report 506,” Southern California Coastal Water Re- search Project, Costa Mesa, 2007. ftp://ftp.sccwrp.org/pub/download/DOCUMENTS/TechnicalReports/506_beta_testing.pdf
S. Siefring, M. Varma, E. Atikovic, L. Wymer and R. Haugland, “Improved Real-Time PCR Assays for the Detection of Fecal Indicator Bacteria in Surface Waters with Dif- ferent Instrument and Reagent Systems,” Journal of Water and Health, Vol. 6, 2008, pp. 225-237.doi:10.2166/wh.2008.022
R. Bushon, C. Likirdopulos and A. Brady, “Comparison of Immunomagnetic Separation/Adenosine Triphosphate Rapid Method to Traditional Culture-Based Method for E. coli and Enterococci Enumeration in Wastewater,” Water Research,, Vol. 43, No. 19, 2009, pp. 4940-4946. doi:10.1016/j.watres.2009.06.047
J. Lavender and J. Kinzelman, “A Cross Comparison of qPCR to Agar-based or Defined Substrate Test Methods for the Determination of Escherichia coli and Enterococci in Municipal Water Quality Monitoring Programs,” Wat. Res., Vol. 43, No. 19, 2009, pp. 4967-4979.doi:10.1016/j.watres.2009.08.010
J. Kinzelman, R. Bushon, S. Dorevitch and R.T. Noble, “Com- parative Evaluation of Molecular and Culture Me- thods for Fecal Indicator Bacteria for Use in Inland Recreational Waters,” Water Environment Research Foundation, IWA Publishing, London, 2011, 360 p.
US EPA, “Recreational Water Quality,” United States Environmental Protection Agency, Washington DC, 2011.
J. Kinzelman, C. Ng, E. Jackson, S. Gradus, and R. Bagley, “Enterococci as Indicators of Lake Michigan Recreational Water Quality: Comparison of Two Methodologies and Their Impacts on Public Health Regulatory Events,” Applied and Environmental Microbiology, Vol. 69, No. 1, 2003, pp. 92-96. doi:10.1128/AEM.69.1.92-96.2003
R. Converse, J. Griffith, R. T. Noble, R. Haugland, K. Schiff and S. Weisberg, “Correlation between Quantitative PCR and Culture-Based Methods for Measuring Enterococcus spp. over Various Temporal Scales at Three California Marine Beaches,” Applied and Environmental Microbiology, Vol. 78, No. 4, 2012, pp. 1237-1242.doi:10.1128/AEM.07136-11
M. Gregory and E. Frick, “Indicator Bacteria Concentrations in Streams of the Chattahoochee River National Recreation Area, March 1999-April 2000,” Proceedings 2001 GWRC Conference, Athens, 26-27 March 2001, pp. 510-513.
J. Kinzelman and S. McLellan, “Success of Science- Based Best Management Practices in Reducing Swimming Bans—A Case Study from Racine, Wisconsin, USA,” Aquatic Ecosystem Health Manage, Vol. 12, No. 2, 2009, pp. 187-196. doi:10.1080/14634980902907466
Wisconsin Department of Natural Resources (WI DNR), “Beach Monitoring Program Requirements, 2011. http://dnr.wi.gov/org/water/wm/wqs/beaches/BeachMonitoringRequirements.pdf
J. Kinzelman, A. Dufour, L. Wymer, G. Rees, K. Pond and R. Bagley, “Comparison of Multiple Point and Composite Sampling for Monitoring Bathing Water Quality,” Lake and Reservoir Management, Vol. 22, No. 2, 2006, pp. 95- 102. doi:10.1080/07438140609353887
US EPA, “Method 1603: Escherichia coli (E. coli) in Water by Membrane Filtration Using Modified Mem- brane-Thermotolerant Escherichia coli Agar (Modified m- TEC),” US EPA Office of Water, Washington DC, 2002.
A. Blackwood, S. Yu, J. Gregory and R. T. Noble, “Rapid qPCR Assays for Escherichia coli and Enterococcus in Recreational Waters: Equivalent to Existing Methods?” Proceedings ASM National Meeting, Orlando, 21-26 May 2006. http://ieg.ou.edu/ASM2006/data/papers/Q_494.htm
R. T. Noble, A. Blackwood, J. Griffith, C. McGee and S. Weisberg, “Comparison of Rapid Quantitative PCR- Based and Conventional Culture-Based Methods for Enumeration of Enterococcus spp. and Escherichia coli in Recreational Waters,” Applied and Environmental Microbiology, Vol. 76, No. 22, 2010, pp. 7437-7443.doi:10.1128/AEM.00651-10
T. Wade, R. Calderon, E. Sams, M. Beach, K. Brenner, A. Williams, and A. Dufour, “Rapidly Measured Indicators of Recreational Water Quality are Predictive of Swim- ming-Associated Gastrointestinal Illness,” Environmental Health Perspectives, Vol. 114, No. 1, 2006, pp. 24-28. doi:10.1289/ehp.8273
T. Wade, et al., “Rapidly Measured Indicators of Recreational Water Quality and Swimming-Associated Illness at Marine Beaches: A Prospective Cohort Study,” Environmental Health, Vol. 9, No. 66, 2010.
A. Mednick and D. Watermolen, “Beach Pathogen Forecasting Tools: Pilot Testing, Outreach, and Technical Assistance,” Wisconsin Department of Natural Resources, Bureau of Science Services, Miscellaneous Publication, 2009.
J. Telech, K. Brenner, R. Haugland, E. Sams, A. Dufour, L. Wymer and T. Wade TJ, “Modeling Enterococcus Densities Measured by Quantitative Polymerase Chain Reaction and Membrane Filtration Using Environmental Conditions at Four Great Lakes Beaches,” Water Research, Vol. 43, No. 19, 2009, pp. 4947-4955.doi:10.1016/j.watres.2009.07.002