INTRODUCTION
Determination of human impacts on stream ecosystems has been a topic of concern for many years
(1-4). Many attempts have been made to quantify the ecological damage to streams caused by pollution
and/or habitat degradation (5-11). Monitoring of chemical water quality alone fails to include biological
water quality parameters that may be critical to a valid assessment of impact. Chemical monitoring
often does not account for human-caused habitat perturbation that can impair stream function. Effective
monitoring programs include assessments of physical habitat and biotic integrity because the ability to
sustain balanced biotic communities is a reliable indicator of stream health (10,12).
Ecological assessments of this sort are based on the premise that sites can be compared to
nonimpacted or minimally impacted reference sites (4,12-14). Reference streams are streams that have
been assessed and determined to have satisfactory water quality, habitat quality, or both. Positive
reference streams have both high water quality and habitat quality; these streams are often located in
areas of minimal anthropogenic influence and have optimal conditions for their ecoregion. Negative
reference streams have high water quality but poor habitat quality; these streams demonstrate alteration
of stream function by habitat degradation only.
Biological integrity is the ability to support and maintain a balanced, integrated, adaptive
community of organisms having a species composition, diversity, and functional organization
comparable to that of the natural habitat of the region (8). The Index of Biotic Integrity (IBI) is a
broad-based, quantitative, multi-parameter tool based on the composition of fish or other biological
communities (2). IBI uses several metrics that vary by ecoregion. These metrics examine both structural
and functional characteristics of biological communities. Each metric is qualitatively assigned a
quantitative score that is indica62
A.
INTRODUCTIONDetermination of human impacts on stream ecosystems has been a topic of concern for many years(1-4). Many attempts have been made to quantify the ecological damage to streams caused by pollutionand/or habitat degradation (5-11). Monitoring of chemical water quality alone fails to include biologicalwater quality parameters that may be critical to a valid assessment of impact. Chemical monitoringoften does not account for human-caused habitat perturbation that can impair stream function. Effectivemonitoring programs include assessments of physical habitat and biotic integrity because the ability tosustain balanced biotic communities is a reliable indicator of stream health (10,12).Ecological assessments of this sort are based on the premise that sites can be compared tononimpacted or minimally impacted reference sites (4,12-14). Reference streams are streams that havebeen assessed and determined to have satisfactory water quality, habitat quality, or both. Positivereference streams have both high water quality and habitat quality; these streams are often located inareas of minimal anthropogenic influence and have optimal conditions for their ecoregion. Negativereference streams have high water quality but poor habitat quality; these streams demonstrate alterationof stream function by habitat degradation only.Biological integrity is the ability to support and maintain a balanced, integrated, adaptivecommunity of organisms having a species composition, diversity, and functional organizationcomparable to that of the natural habitat of the region (8). The Index of Biotic Integrity (IBI) is abroad-based, quantitative, multi-parameter tool based on the composition of fish or other biologicalcommunities (2). IBI uses several metrics that vary by ecoregion. These metrics examine both structuraland functional characteristics of biological communities. Each metric is qualitatively assigned aquantitative score that is indica62A.
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