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Biological Response Signatures

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Ohio Case Studies

Biological indicators are both accurate and sensitive measures of the health of waterways and they can also be used to diagnose sources and causes of pollution. Definite patterns exist in the responses of biological communities to stress (pollution), and finding these patterns can show what types of pollution are present, and sometimes the source of those problems. When the response patterns of the various metrics and components of IBIs (Indices of Biotic Integrity) are identified, these unique combinations of biological community characteristics that aid in distinguishing one impact type over another are referred to as "Biological Response Signatures."

Metrics

When conducting biological assessments, measurements are taken in the field or lab. Metrics (or biological attributes) for each assemblage sample (e.g., benthic invertebrates, fish, periphyton, macrophytes) are calculated from these measurements. The following table presents an example of representative metrics for each type of assemblage.

Biological Assemblage Metric Response to Stress
Benthic Macroinvertebrates No. of taxa Reduced
ETO taxa (ephemeroptera, trichoptera, odonates) Reduced under enrichment, DO, stress
% intolerant species Reduced
% suspension feeders Reduced
Fish No. of taxa Reduced
% piscivores Reduced
No. of intolerant species Reduced
No. of sunfish species Reduced
Macrophytes No. of taxa Low
% dominant species (by weight) High
No. of exotic species High
Periphyton Species richness Not Determined
Pollution Tolerance Index for Diatoms Not Determined
Achnanthes minutissima Not Determined
Shannon Diversity (for diatoms) Not Determined

Each metric is then assigned a score which is related to its deviation from the reference (or expected) site values. In more complicated studies, multimetric indices can be calculated, which is the sum of all the metric scores within each biological assemblage. <more on metrics>

For more information on biological response signatures:

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Please see the discussions on the diagnostic value of biological indicators in EPA's Stressor Identification Evaluation Manual and Ohio EPA's discussion on Biological Response Signatures (pdf file) and the Area of Degradation Value.

To learn more about metrics please visit the following sites:

Biological Indicators | Aquatic Biodiversity | Statistical Primer

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