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Steps in Developing a Bioassessment and Biocriteria Program
Biocriteria Links
Biological Assessment of Reference Sites
Conducting Bioassessments
Biological assessment is essentially an interpretive function. It seeks to evaluate the biological condition of a waterbody by directly measuring resident biota in surface waters and other data, and then comparing the results against criteria that describe the qualities that must be present to support a desired condition in a waterbody. The intent is to detect biological responses to pollution or other perturbations, distinguishing between changes due to natural variability and those impacts due to human activities. Coupled with habitat assessment, bioassessment helps identify probable causes of impairment not detected by physical and chemical water quality analyses alone, such as non-point source pollution and contamination, erosion, poor or changing land-use practices.
Both the biotic and physical habitat characteristics are surveyed using standardized methods within each ecosystem classification. To develop the discriminatory power of the metrics within a class, the survey should include both impaired and minimally impaired sites, and should sample two or more biological assemblages (e.g., infauna, fish, epifauna, macrophytes, plankton). Expanding survey tiers offer increasing refinement and complexity of the survey effort from the number of individuals and biological assemblages sampled, to the taxonomic level of identification, the extent of the physical environment sampled, and the number of sample replicates taken. Each tier represents a greater investment of resources over lower tiers, and a greater level of resolution.
Chapter 6 of Biological Criteria: National Program Guidance for Surface Waters (1990), provides more information on biological assessments including selecting aquatic community components, biological survey design, and sampling design.
For further information on biological assessment, see:
On-Line Publications on Biological Indicators, Assessment and Criteria.