|Lerch, Robert - Bob|
Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract only
Publication Acceptance Date: 12/29/2003
Publication Date: 5/22/2004
Citation: Stanley, L., Lerch, R.N., Kremer, R.J. 2004. Fecal bacterial contamination of a karst watershed in central Missouri. American Society for Microbiology Annual Meeting, New Orleans, LA. 04-GM-A-4366-ASM. Interpretive Summary:
Technical Abstract: The Bonne Femme watershed of Boone County, Missouri includes a combination of areas originating from glacial and loess uplands with mainly production agriculture land uses to the lower reaches characterized by karst topography with oak-hickory Ozark forests. Losing stream hydrology in the karst portion of the watershed creates a particularly vulnerable setting for ground water contamination because of the direct connection to surface water. Previous studies in the watershed have shown that surface and sub-surface stream contamination by fecal coliforms was the major water quality problem within the watershed. The objectives of this study were to compare fecal contamination within the major sub-watersheds and relate contamination to land use, hydrology, and time of year. Ten sub-watersheds within the Bonne Femme watershed were sampled weekly, for one month per quarter in the third and fourth quarters of 2003 for fecal coliforms, E. coli, and enterohemorrhagic (EHEC) E. coli O157:H7. Bacterial enumeration was determined by the membrane filtration technique utilizing a combination of selective growth media and incubation temperatures to isolate the desired thermotolerant population. Results of fecal coliform contamination of water within the major sub-watersheds were primarily driven by hydrology. Under low-flow stream conditions, fecal coliforms counts ranged (geometric means) from 25 to 234 CFU/100 mL with only one of ten sub-watersheds exceeding the EPA limit for whole body contact. However during a high-flow event, geometric mean counts ranged from 2,818 to 38,018 CFU/100mL with all sub-watersheds, exceeding EPA's limit. Statistical analysis of fecal coliform data revealed that sub-watershed, low-flow fecal coliform counts were significantly different, but there was no significant difference in fecal counts due to the time of year. This indicated that land-use among the sub-watersheds also affected the extent of fecal contamination, but not as strongly as hydrologic conditions. However, seasonal differences in fecal contamination, at least for the 3rd and 4th quarters of 2003, had little impact on fecal contamination.