Biological-Community Composition in Small Streams and its Relations to Habitat, Nutrients, and Land Use in Agriculturally Dominated Landscapes in Indiana and Ohio, 2004, and Implications for Assessing Nutrient Conditions in Midwest Streams

The objective of this study was to relate algal-, invertebrate-, and fish-community composition to habitat, nutrients, and land-use variables in small streams in agriculturally dominated landscapes of the Midwest in Indiana and Ohio. Thirty sample locations were selected from a single ecoregion; all were small wadable streams within agriculturally dominated landscapes with similar substrate and canopy. Biological and nutrient samples were collected during stable flow conditions in August 2004. Canonical correspondence analysis was used to determine which variables most influenced each community. Total phosphorus concentrations significantly influenced the depositional-targeted habitat algal-diatom community and the richest-targeted habitat invertebrate community. Multivariate statistical analysis showed that habitat variables were more influential to the richest-targeted habitat algal-diatom and fish communities than nutrient concentrations. Although the nutrient concentrations measured during this study indicate that most streams were not eutrophic, the biological communities were dominated by eutrophic species, suggesting streams sampled were eutrophic. Consequently, it was concluded that biological relations to nutrients in agriculturally dominated landscapes are complex and habitat variables should be included in biological assessments of nutrient conditions in agriculturally dominated landscapes.