title: Comparison of beach bacterial water quality indicator measurement methods.
abstract: Three methods (membrane filtration, multiple tube fermentation, and chromogenic substrate technology kits manufactured by IDEXX Laboratories, Inc.) are routinely used to measure indicator bacteria for beach water quality. To assess comparability of these methods, quantify within-laboratory variability for each method, and place that variability into context of variability among laboratories using the same method, 22 southern California laboratories participated in a series of intercalibration exercises. Each laboratory processed three to five replicates from thirteen samples, with total coliforms, fecal coliforms or enterococci measured depending on the sample. Results were generally comparable among methods, though membrane filtration appeared to underestimate the other two methods for fecal coliforms, possibly due to clumping. Variability was greatest for the multiple tube fermentation method. For all three methods, within laboratory variability was greater than among laboratories variability.
authors.affiliation: University of North Carolina at Chapel Hill, Institute for Marine Sciences, Morehead City, NC, USA. rtnoble@email.unc.edu
authors.forename: Rachel T
authors.initials: RT
authors.lastname: Noble
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Weisberg
authors.forename: Molly K
authors.initials: MK
authors.lastname: Leecaster
authors.forename: Charles D
authors.initials: CD
authors.lastname: McGee
authors.forename: Kerry
authors.initials: K
authors.lastname: Ritter
authors.forename: Kathy O
authors.initials: KO
authors.lastname: Walker
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Vainik
mesh_terms: D002138:Calibration; D002140:California; D004777:Environment; D004784:Environmental Monitoring / Q000379:methods*; D005285:Fermentation; D005374:Filtration; D011786:Quality Control; D012016:Reference Values; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D014873:Water Pollutants