Bioassessment of streams using macroinvertebrates: are the chironomidae necessary?

We compared the sensitivity of commonly used bioassessment metrics to detect organic impairment of streams using data sets that varied only in the inclusion or exclusion of Chironomidae identified to genus. We evaluated situations in two contrasting ecoregions of Missouri, U.S.A., the Ozark ecoregion and the Prairie ecoregion where Chironomidae comprise an average of 32 and 42%, respectively, of the total number of individuals. The without-Chironomidae data showed either identical or greater sensitivity than with Chironomidae data in every case when using the metrics total taxa, biotic index. Shannon's diversity index, and % dominant taxon. We conclude that bioassessment programs employing commonly-used metrics that usually incorporate Chironomidae may become more efficient by eliminating Chironomidae from the protocols and using those resources for analyzing additional sites.