WWRC 84-22
Change in Bacterial Populations Downstream in a Wyoming Mountain Drainage Basin
Abstract
Ten bacteriological tests were utilized to monitor different bac
terial populations found in water samples taken from streams
draining high mountain rangeland. Livestock grazing and recrea
tion constituted the major uses of the study area. Vegetation types
were typical of those found in other sub-alpine and alpine zones in
the central Rocky Mountains. Results show differences in counts
of bacteria between sampling sites along individual streams
sampled with the exception of those organisms capable of reducing
nitrate were not significant. A seasonal variation in the numbers of
bacteria were found between streams. This variation is not fully
explained by drainage basin areas or related to runoff. In contrast,
within each stream counts varied with season and could be related
to runoff. Bacterial populations which indicate fecal pollution
were low and probably derived from animals not man. Wet meadows
and bog areas under snow may be possible sources for sulfate
reducing bacteria and those organisms capable of reducing nitrate.
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