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THE USE OF MICROBIAL INDICATORS FOR MONITORING STREAM SANITARY AND ECOLOGICAL CONDITION
Citation:
Bracken, C. L., C W. Hendricks, AND A. K. Harding. THE USE OF MICROBIAL INDICATORS FOR MONITORING STREAM SANITARY AND ECOLOGICAL CONDITION. Presented at James A. Vomocil Water Quality Conference, Corvallis, OR, November 1, 2000.
Description:
We measured traditional public health indicators of sanitary condition, including heterotrophic plate counts, total coliforms, fecal coliforms, and E. coli using membrane filtration from several sites in the John Day watershed of eastern Oregon and from Oak Creek and Thomas Creek in the Willamette Valley. In addition, we assessed in situ physiological diversity using Biologa GN microtiter plates. These plates test the ability of an organism to utilize or oxidize a pre-selected panel of different carbon sources, which is colorimetrically measured with tetrazolium dye. The procedure yields a characteristic pattern of purple wells, or Substrate Utilization Pattern (SUP), which may be related to other measures of stream ecological and sanitary condition such as bacterial plate counts, stream chemistry, and anthropogenic stressors.
In previous water quality surveys, we have found the low inoculum densities that are typical of streams in Oregon preclude the use of Biolog. To overcome this difficulty, we have centrifuged a portion of each sample to concentrate the bacterial population tenfold. Using cluster analysis, we compared the discriminating power of Biolog SUP's in plates inoculated with concentrated water (treatment plates) to those inoculated with unconcentrated water (control plates). For most of the samples, treatment plates were more tightly clustered than control plates. This suggests that by concentrating the microbial community, we may be able to greatly increase the precision of Biolog SUP comparisons among ecologically different stream samples.