Little attention has been given to the assessment of macroinvertebrate assemblages in low gradient streams occurring within agricultural regions of the Central Irregular Plains ecoregion of Missouri. These landscapes are mosaics of pastures, row crops, and small forests with scattered patches of urbanization and conservation areas. To determine appropriate metrics for assessing community differences, six stream sites adjacent to agricultural land uses (combined influence of pasture and row crop) or within conservation areas were sampled for aquatic macroinvertebrates in spring 2002. Six metrics (taxonomic richness, Biotic Index, EPT richness, Shannon diversity, percent Oligochaeta, and percent Diptera and non-insects) were used to compare community structures among sites. Most sites were dominated by Oligochaeta and other taxa in the collector/gatherer functional feeding group. Individual t-tests for each metric were used to test for differences between land uses. The Biotic Index was the only metric to show a significant difference between the two land use types (p=0.038). The mean Biotic Index value of the conservation areas was lower than that of the agricultural land uses. The Biotic Index had the lowest coefficient of variation whereas the EPT richness had the highest, indicating that certain metrics may be more useful than others for comparing community structures in this region.
Keywords: biological monitoring, filter strips
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