The diurnal presence of the culturable bacterial indicators of fecal contamination in the water environment has been shown to be highly variable over time due to natural die-off and injury from effects of sunlight and other environmental stressors. Molecular analytes of a quantitative polymerase chain reaction (qPCR) method for measuring fecal contamination degrade considerably slower than the alternative of culturable fecal indicator bacteria. The rapid qPCR method holds the promise of more timely notification decisions with respect to postings or closure being made on the basis of microbial water quality samples collected earlier on the same day. In the case of culture-based methods requiring a 24 h or longer incubation period, decisions must be based on samples collected no sooner than the previous day. To examine the effect of this lag in assay results, temporal stability of a molecular Enterococci target analyte with that of traditional culture-based cells is compared using data from USEPA studies conducted between 2003 and 2007 on seven freshwater and marine beaches that were impacted by publicly-owned treatment works. Generally, levels of the molecular indicator were more consistent throughout the day between 8:00 am and 3:00 pm. The difference in temporal consistency is even more pronounced when the 24-h lag in culture-based results is taken into account.

由于自然死亡和阳光和其他环境压力因素的影响造成的损伤，水环境中粪便污染的可培养细菌指标的昼夜存在已被证明随时间变化很大。用于测量粪便污染的定量聚合酶链式反应 (qPCR) 方法的分子分析物降解比可培养粪便指示细菌的替代方法要慢得多。快速 qPCR 方法有望根据当天早些时候收集的微生物水质样本做出关于张贴或关闭的更及时通知决定。对于需要 24 小时或更长时间潜伏期的基于培养的方法，必须根据不早于前一天收集的样本做出决定。使用美国环保署 2003 年至 2007 年间对受公有处理工程影响的七个淡水和海洋海滩进行的研究数据，将肠球菌目标分析物与传统培养细胞的目标分析物进行了比较。一般来说，分子指示剂的水平在上午 8:00 到下午 3:00 之间全天更加一致。当考虑到基于培养结果的 24 小时滞后时，时间一致性的差异更加明显。