Indicator Bacterial Survival in Stream Sediments

Indicator Bacterial Survival in Stream Sediments -...

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Indicator Bacterial Survival in Stream Sediments Brett M. Sherer, J. Ronald Miner,* James A. Moore, and John C. Buckhouse ABSTRACT The impact of grazing cattle (Bostauras) on water quality has been the subject of considerable interest as water quality standards become more restrictive. Benthic sediments have been found to harbor sig- nificantly higher concentrations of enteric bacteria than the overlying water. In this study, the survival of fecal coliform and fecal strepto- cocci organisms was demonstrated to be significantly longer in sedi- ment laden waters than in those without sediment and further the survival was longer in the sediment-laden waters than in a supernatant from that same sediment suspended in water. Fecal coliform and fecal streptococci bacteria revealed half-lives from II to 30 d and 9 to 17 d, respectively when incubated with sediment. This is longer than when they are similarly incubated without sediment. T HE IMPACT of grazing cattle (Bostauras) on water quality has been the subject of considerable in- terest as water quality standards become more widely applied. Enteric organisms from grazing animals can enter a stream in runoff from the grazing lands or they may be directly deposited into the water by the ani- mals. Sampling data have revealed that the presence of enteric bacteria persists in a stream, even after the animals have been removed (Gary and Adams, 1985; Sherer et al., 1988; Stephenson and Street, 1978). It is this persistence of microorganisms and the continual interaction between sediment-trapped bacteria and the overlying water that prompted this investigation. BACKGROUND When cattle are present in a pasture and have access to a stream as their water source, they deposit a por- tion of their daily fecal matter directly into the stream (Larsen et al., 1988). Once fecal matter enters the stream (Biskie et al., 1988), the majority of the bac- teria settle to the bottom and can either die or be resuspended. Several researchers have reported re- covering enteric organisms in the sediment when they could not be detected in the overlying water (Gerba et al., 1977; Bitton et al., 1982, Gerba and McLeod, 1976; Loutit and Lewis, 1985). Bacteria in the sedi- ment create a potential for elevated bacterial concen- trations in the overlying water for an extended period of time (Jawson et al., 1982). Benthic sediments have been found to harbor significantly higher concentra- tions of enteric bacteria than the overlying water (Tun- nicliff and Brickler, 1984; Van Donsel and Geldreich, 1971; Sherer et al., 1988; Lewis et al., 1986). LaBelle et al. (1980) found that viruses in estuarine sediments had a positive correlation to the number of fecal col- iforms in sediments; however, no correlation was found B.M. Sherer, Bonneville Power Administration, P.O. Box 491- MMPB, Vancouver, WA 98666; J.R. Miner and J.A. Moore, Bioresource Engineering Dep., Oregon State Univ., Corvallis, OR 97331-3906; and J.C. Buckhouse, Dep. of Rangeland Resources,
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Indicator Bacterial Survival in Stream Sediments -...

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