|Comparison of bacterial indicator analysis methods in stormwater-affected coastal waters|
Noble, R.T.; Leecaster, M.K.; McGee, C.D.; Weisberg, S.B.; Ritter, K. (2004). Comparison of bacterial indicator analysis methods in stormwater-affected coastal waters. Wat. Res. 38(5): 1183-1188
In: Water Research. Elsevier: Oxford; New York. ISSN 0043-1354, more
|Authors|| || Top |
- Noble, R.T.
- Leecaster, M.K.
- McGee, C.D.
- Weisberg, S.B.
- Ritter, K.
Membrane ﬁltration (MF) and multiple tube fermentation (MTF) have been used for decades to measure indicatorbacteria levels in beach water samples, but new methods based on chromogenic substrate (CS) technology are becomingincreasingly popular. Only a few studies have compared results among these methods and they have generally beenbased on samples collected from a limited number of sites during dry weather. In this study, samples were collectedfrom 108 sites the day after a major rainstorm, and three indicator bacteria (total coliforms (TCs), fecal coliforms (FCs)or E. coli, and enterococci (EC)) were each measured using MF, MTF, and CS. Sampling sites were selected using astratiﬁed random design, stratiﬁed by open sandy beach, rocky shoreline, and beach areas near urban runoff outlets. The CS results were found to be highly correlated with both MF and MTF for all three indicators regardless of whetherthe samples were taken along open shoreline or near a runoff outlet. While correlated, TC values were higher using theCS method, consistent with other studies that have demonstrated false positives with this method. FC values were 12%lower with CS, reﬂecting the speciﬁcity of the CS method for E. coli rather than for the entire FC group. No signiﬁcantdifferences were observed for EC, although some differences were observed within speciﬁc laboratories. Differences forall of these indicators were small enough that, when assessed categorically, there was more than 90% agreementbetween CS methods and either MF or MTF methods as to whether State of California Beach Water Quality Standardswere met or exceeded.