among programs [146]. This process is used to evaluate programs with respect to
13 critical elements within three general categories: study design, methods implementation, and data interpretation. The process considers logistic feasibility and
cost-effectiveness, calling for the highest methodological and data-quality standards that are reasonably attainable given existing technological and monetary
constraints. When high-quality methods exist, new bioassessment programs should
employ methods consistent to these to maximize efficiency (i.e., use of preexisting
datasets) and historical significance.
Q: What are the most important recent developments that have improved
comparability among assessment programs?
A: In addition to the critical elements process, the Biological Condition Gradient
approach (BCG, [45]) provides a framework for developing consistent, meaningful,
and understandable aquatic life use standards and is applicable to a wide variety
of monitoring strategies and assemblages. The BCG establishes a baseline by
employing best professional judgment within an organized framework whereby
experts assign bioassessment samples to ecological condition tiers. Biologists
trained to use the BCG produce highly consistent evaluations of site conditions.
The use of the BCG should greatly facilitate the comparability of bioassessments
conducted by different agencies and using different protocols.
Large-scale monitoring programs, such as the USEPA National Aquatic
Resource Survey, are of great importance. This nationwide assessment program
includes standardized sampling protocols and a probabilistic study design for the
assessment of US streams, rivers, lakes, wetlands, and coastal waters. The ongoing
intercalibration exercise, a key component of the European Union (EU) Water
Framework Directive (EC 2000/60/EC; [147]), and resulting multi-country aquatic
ecosystem surveys are other important examples. The major advantage of these
programs is the development of consistent and rigorous protocols that allow for
large-scale biological assessments of aquatic ecosystems.
Expert 2 Simone D. Langhans, Ph.D.—Humboldt Research Fellow, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
Q: What factors are most important in limiting comparability among
bioassessment schemes?
A: Variability in the definition of reference conditions (i.e., the allowable amount
of impairment within the reference dataset) can hinder the comparison of index
scores from different assessment programs. Index scores are typically an expression
of how similar a site is from the reference state; therefore, the use of similar
reference criteria facilitates comparability among assessment indices.
The expression of index scores in a continuous manner, rather than as categorical
ratings, is helpful when aggregating scores derived from different assessment
schemes. Due to their discrete nature, categorical ratings may differ for scores
that are actually quite similar; therefore, the most reliable aggregated indices are
based on continuous scoring systems. For management purposes, categorical
ratings can be applied after aggregation. Langhans et al. [141] present a method
for standardizing metric scores or attribute measures among indices to a continuous
Principles for the Development of Contemporary Bioassessment Indices for. . .
255
13 critical elements within three general categories: study design, methods implementation, and data interpretation. The process considers logistic feasibility and
cost-effectiveness, calling for the highest methodological and data-quality standards that are reasonably attainable given existing technological and monetary
constraints. When high-quality methods exist, new bioassessment programs should
employ methods consistent to these to maximize efficiency (i.e., use of preexisting
datasets) and historical significance.
Q: What are the most important recent developments that have improved
comparability among assessment programs?
A: In addition to the critical elements process, the Biological Condition Gradient
approach (BCG, [45]) provides a framework for developing consistent, meaningful,
and understandable aquatic life use standards and is applicable to a wide variety
of monitoring strategies and assemblages. The BCG establishes a baseline by
employing best professional judgment within an organized framework whereby
experts assign bioassessment samples to ecological condition tiers. Biologists
trained to use the BCG produce highly consistent evaluations of site conditions.
The use of the BCG should greatly facilitate the comparability of bioassessments
conducted by different agencies and using different protocols.
Large-scale monitoring programs, such as the USEPA National Aquatic
Resource Survey, are of great importance. This nationwide assessment program
includes standardized sampling protocols and a probabilistic study design for the
assessment of US streams, rivers, lakes, wetlands, and coastal waters. The ongoing
intercalibration exercise, a key component of the European Union (EU) Water
Framework Directive (EC 2000/60/EC; [147]), and resulting multi-country aquatic
ecosystem surveys are other important examples. The major advantage of these
programs is the development of consistent and rigorous protocols that allow for
large-scale biological assessments of aquatic ecosystems.
Expert 2 Simone D. Langhans, Ph.D.—Humboldt Research Fellow, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
Q: What factors are most important in limiting comparability among
bioassessment schemes?
A: Variability in the definition of reference conditions (i.e., the allowable amount
of impairment within the reference dataset) can hinder the comparison of index
scores from different assessment programs. Index scores are typically an expression
of how similar a site is from the reference state; therefore, the use of similar
reference criteria facilitates comparability among assessment indices.
The expression of index scores in a continuous manner, rather than as categorical
ratings, is helpful when aggregating scores derived from different assessment
schemes. Due to their discrete nature, categorical ratings may differ for scores
that are actually quite similar; therefore, the most reliable aggregated indices are
based on continuous scoring systems. For management purposes, categorical
ratings can be applied after aggregation. Langhans et al. [141] present a method
for standardizing metric scores or attribute measures among indices to a continuous
Principles for the Development of Contemporary Bioassessment Indices for. . .
255