Use of Benthic Macroinvertebrate Indices to Assess Aquatic Health in a Mixed-Landuse Watershed

ABSTRACT

Seven family-level metrics were determined from benthic macroinvertebrate samples collected monthly across four different landuse sites in the Cazenovia Creek watershed in western New York. We evaluated which metrics were most appropriate for, and effective in, discerning differences among the sites. Dramatic and consistent seasonal differences in metric scores were observed across all sites. All metric scores indicated markedly better biological health during winter months than during summer months. The biological impairment designation was highest in the summer at the suburban and agricultural sites. Coefficients of variation were considerably greater at the lower stream order sites. The metrics that were most appropriate and effective in assessing benthic assemblage health in this study were: richness, percent model affinity, family-level biotic index, and Ephemeroptera-Plecoptera-Trichoptera index. These indices correlated with a low amount of redundancy in a Pearson matrix, had significant discriminatory power in assessing biological impairments across sites, and had low variation within sites and seasons. This suggests these metrics should be selected for bioassessments in similar Great Lakes watersheds.