No abstract

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. Sampling protocols for indicator bacteria in freshwater streams recommend capture and retrieval of samples from the mid-water column directed into the current and within the deepest portion of the channel to prevent collection of either benthic particles or surface films. 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 (p ≥ 0.25) upon such indicator bacteria numbers. Additionally, these data are the first to show that concentrations of the common bacterial indicator, E. coli, are homogeneously distributed throughout both lateral area and vertical water column within/near a single sampling location of a moving water body up to 245 cubic feet per second (cfs) discharge. Moreover, one data point (bacterial sample) appears to represent the overall bacterial concentration of a small freshwater stream obtained from any single sampling location within/near the main channel for a given date and time. 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.

Many studies report the relationship between coliform indicator bacteria levels and the overall quality of environmental water for public use. This study, an outgrowth of a long-term watermonitoring program within the upper Appomattox River (Virginia) watershed, employs a zebrafish model to examine the relationship between impaired stream water and aquatic vertebrate development. We report results that suggest an expansion of the indicator bacteria concept, showing a possible relationship between waters containing high levels of the indicator bacterium, Escherichia coli (E. coli), with developmental defects upon zebrafish embryos. These effects are not directly attributable to bacterial presence, as filtered test waters void of bacteria produce the same results in embryos, indicating these developmental defects are due to the presence of other toxins or contaminants. Fish embryos exposed to the test waters show reduced survivorship and altered brain and heart development. Furthermore, fish surviving to adulthood exhibit altered gonads and skewed sex ratios. We suggest that this broadly focused approach examining the complex interactions (biotic and abiotic) within raw water sources could be used in conjunction with traditional chemical assays and/or dose-response studies on vertebrate models for a more complete analysis of stream water quality conditions.