Evaluating
Stream Bioassessment Protocols using Data from the Clark Fork’s Ecoregion
Wease Bollman, Rhithron
Biological Associates, 1845 South 12th West, Missoula, MT
ABSTRACT: A
proposed method for the evaluation of macroinvertebrate bioassessment protocols
is described in this study. The Montana Department of Environmental Quality
(Montana DEQ) uses a modification of US EPA’s Rapid Bioassessment Protocols
for stream assessment and monitoring. These protocols use a battery of
macroinvertebrate community descriptors, or metrics, as indicators of biotic
health; the metrics are based upon tenets of ecological theory and field
observations and remained largely untested for sensitivity to the effects of
human activities.
To evaluate the metric battery in current use, 93 stream sites were
sampled in the Montana Valley and Foothill Prairies ecoregion (which includes
the river valleys and foothills of the Clark Fork Basin) . These sites were
classified as highly impacted by human activities, moderately impacted and less
impacted, based upon visual assessment of habitat and watershed information.
Twenty-two metrics, including those comprising the state’s protocol, were
tested. Eight metrics were able to distinguish less impaired sites from highly
impaired sites. Seven of these impact-sensitive metrics were highly correlated
with habitat assessment parameters. Anthropogenic impacts explained over
one-third of the variability in six metrics. Based on these results, a battery
of seven metrics was assembled. This metric battery proved to be more sensitive
to impact, better related to habitat variables, and more consistent in assigning
impairment categories than the battery used by Montana DEQ.
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