Homogeneous Distribution of Escherichia coli Measured within the Vertical Water Column of Small, Freshwater Streams

Sampling for coliform bacterial indicators such as Escherichia coli (E. coli) provides a universally accepted gauge of the microbiologic quality of fresh surface waters worldwide. Protocols for the capture, preservation, and analysis of indicator bacteria collected from moving waters (e.g., rivers, streams, canals, etc.) parallel those for collecting bacteria from standing waters (e.g., ponds, lakes, and impoundments). Strict depth- and width-integrated rules established for testing moving waters are likely a result of the historical precedence of our knowledge of bacterial stratification in standing waters. Chi-square analyses of multiple stratified samples captured on the same date and time reveal that variability in sampling position at specified depths within the main stream column or within randomly chosen locations within the main stream channel has no effect upon such indicator bacteria numbers. These findings suggest some latitude in sampling strategies for assessing small freshwater streams for indicator bacteria such as E. coli for workers in both environmental and public health fields.