Bioassessment of streams using macroinvertebrates: Are the chironomidae necessary?

We compared the sensitivity of commonly used bioassessment metrics to detec t organic impairment of streams using data sets that varied only in the inc lusion or exclusion of Chironomidae identified to genus. We evaluated situa tions in two contrasting ecoregions of Missouri, U.S.A., the Ozark ecoregio n and the Prairie ecoregion where Chironomidae comprise an average of 32 an d 42%, respectively, of the total number of individuals. The without-Chiron omidae data showed either identical or greater sensitivity than with Chiron omidae data in every case when using the metrics total taxa, biotic index, Shannon's diversity index, and % dominant taxon. We conclude that bioassess ment programs employing commonly-used metrics that usually incorporate Chir onomidae may become more efficient by eliminating Chironomidae from the pro tocols and using those resources for analyzing additional sites.