Characterizing and comparing bioassessment methods and their results: A perspective

Most of the many bioassessment methods currently in use in the United States produce data of unknown quality. The results are: 1) uncertainty as to which methods yield accurate information for a given type of site, and 2) missed opportunities to share data among different programs or organizations having potentially comparable methods and data quality. Using a performance-based methods system (PBMS) and benthic macroinvertebrate assessment methods as examples, we offer a framework for characterizing the data quality achieved by a collection-and-analysis method and for determining the comparability of different methods. This framework incorporates 3 steps that: 1) quantify method precision and bias for a single site, using different field personnel and different site classes; 2) quantify method precision, bias, and performance range using multiple reference sites within at least 2 different site classes; and 3) quantify method sensitivity, bias, performance range and-indirectly-accuracy, using test sites (with different levels or types of probable impairment) as well as reference sites. Comparability of methods is judged by the degree of similarity in their performance characteristics rather than in their respective scores or metric values. The PBMS framework could yield several benefits including: documentation of personnel training in the field; realistic requirements for data quality in bioassessment methods so that information gathered is likely to meet program or project needs; greater flexibility in choice of method used; refinement of methods by agencies responsible for long-term monitoring without the loss of historical data; and more sharing of bioassessment information across political boundaries, thus reducing duplication of efforts.