Abstracts Health Sciences

Evaluating microbial indicators of environmental condition in Oregon rivers

by Alan Travis Pennington

Traditional public health bacterial indicators of water quality and the Biolog® system were evaluated to compare their response to other indicators of stream condition with the state of Oregon and between ecoregions (Coast Range, Willamette Valley, Cascades, and Eastern Oregon). Forty-three randomly selected Oregon rivers were sampled during the summer low flow period in 1997 and 1998. Testing included heterotrophic plate counts (HPC), total coliforms, fecal coliforms, E. coli, and Biolog® GN plates. Statewide, HPC correlated strongly with physical habitat and chemistry indicators while fecal coliforms and E. coli were highly correlated only with the river chemistry indicators. Total coliform bacteria did not correlate with either of the above environmental indicators. Dividing the sites by ecoregion, Eastern Oregon was characterized by high HPC, fecal coliforms, E. coli, nutrient loads, and indices of human disturbance, whereas the Cascades ecoregion had correspondingly low counts of these indicators. The Coast Range reflected statewide results and the Willamette Valley presented no consistent indicator pattern. Attempts to separate ecoregions with the Biolog system were not successful nor did a statistical pattern emerge between the first five principle components and the other environmental indicators. Our research has shown that traditional public health microbial indicators may, however, be useful in measuring the effects of anthropogenic stress over large spatial scales.