Graduate Thesis Or Dissertation
 

Bacteria die-off in stream sediments

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vd66w3164

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  • The purpose of this study was to evaluate the impact sediment has on the survival of bacteria in a typical rangeland stream. This information is an important component in determining a time integrated prediction of bacterial numbers in the stream sediment and overlying water. Bacterial survival in stream is a crucial factor in the complex relationship between stream quality and range management. Once this relationship has been defined, it will lead to a scientifically-based, rational process for rangeland management decisions. Bear Creek flows through a semi-arid rangeland in Central Oregon. Two sediment samples (clay loam and sandy loam) were collected from Bear Creek. Sediment samples were combined by weight with fresh bovine feces at 250:1, 20:1, and 6.67:1 ratios (sediment:feces). The inoculated sediment samples and a contaminated water sample were stored a 8°C and monitored to determine the change in concentrations of fecal coliform (FC) and fecal streptococci (FS) with time. Stream sediments were found to increase the survival of fecal coliform and fecal streptococci in an aquatic environment. FC was found to exhibit a significantly lower die-off rate than FS in sediments inoculated with bovine feces. No significant difference was observed in the die-off rate of FS between sediment types or inoculation levels with a half-life ranging from 9 to 12 days. Die-off rates for FC were found (half-life ranging from 13 days to 31.5 days) to be significantly different between inoculation levels and sediment types. No relationships were observed between FC and FS die-off rates to particle size or inoculation level. This study concluded that stream sediment allows enteric bacteria to survive, possibly for several months, in an aquatic environment. Resuspension of these bacteria may account for the erratic FC and FS levels often encountered in water monitoring programs since grab samples of water give only an immediate measure of bacterial levels. If enteric pathogens behave similarly, significant public health hazards could arise. Existing state bacteriological standards and monitoring procedures fail to address these problems. Therefore, a more meaningful and accurate indication of water-quality conditions would be obtained by also monitoring indicator bacteria levels in surface sediments.
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file details ShererBrettMichael1990.pdf 2017-08-14 Pubblico Scaricare