This research was conducted to (1) determine an optimal suite of macroinvertebrate metrics and (2) test the effectiveness of standard EPA biological assessment methods for identification of stream degradation. Invertebrate samples were taken from 18 sites on Bachelor and Brookfield Creeks in Moody County, South Dakota once per month from April through September 1998 and 1999. Data were applied to 51 invertebrate metrics which were (1) randomly selected in sets of 10, (2) grouped as per Plafkin et al. (1989) (3) optimized by minimizing reference site variability and maximizing site discriminatory power (Barbour et al., 1999), and (4) optimized using principal components analysis (PCA). Plafkin and randomly selected metric sets resulted in 60% of stream sites classified as slightly impaired and 40% of sites as moderately impaired. Optimized metrics resulted in 20% of stream sites classified as unimpaired, 47% of sites as slightly impaired, and 33% of sites as moderately impaired. PCA metrics resulted in 47% of sites classified as unimpaired and 53% of sites as slightly impaired. Three sites categorized as slightly impaired using the Plafkin set were considered non-impaired using the optimized set. All sites categorized as slightly impaired using the Plafkin set were considered non-impaired using the PCA set. These results suggest that objective selection of core metrics is necessary to prevent type I errors from biomonitoring investigations.
Proceedings of the South Dakota Academy of Science
Larson, A. M. and Troelstrup, Nels H. Jr., "Optimal Macroinvertebrate Metrics for the Assessment of a Northern Prairie Stream" (2001). Oak Lake Field Station Research Publications. 40.