A Case Study for Comparison of NAWQA and EMAP Protocols for Benthic Macroinvertebrates and Habitat

David A. Peterson ¹, Peter R. Wright², and Jeremy R. Zumberge³ 

¹U.S. Geological Survey, 2617 E. Lincolnway, Suite B, Cheyenne, Wy. 82001
²U.S. Geological Survey, 1728 Lampman Drive, Suite D, Billings, Mt. 59104,
³Wyoming Department of Environmental Quality, 1866 South Sheridan Ave., Sheridan, Wy. 82801

Abstract

Benthic macroinvertebrate communities and habitat measurements are compared for data collected following protocols established by the USGS NAWQA program and by the USEPA EMAP Western Pilot. Samples and measurements at 12 sites were collected by the same personnel for both protocols, in a side-by-side fashion at streams in Wyoming, Montana, and Colorado.

Benthic macroinvertebrate community structure was compared between the data sets using individual metrics and multivariate analysis. Differences in total taxa richness and Ephemeroptera taxa richness between the data sets were significant at the p < 0.05 level after removal of ambiguous taxa. Differences in other metrics generally were not significant, such as richness of Plecoptera and Trichoptera, tolerant taxa, functional feeding groups, diversity, and dominance. Scores calculated for a multi-metric index, the Wyoming Stream Integrity Index, were not significantly different between the data sets. Some differences in community structure between the two data sets could be attributed to differences in subsampling and taxonomic identification procedures. Subsampling procedures appeared to have greater effect on individual metrics, whereas reconciliation of the taxa lists resulted in decreased differences between data sets in multivariate analysis. Procedures are discussed to minimize differences and maximize the comparability and potential cross-utilization of the NAWQA and EMAP macroinvertebrate data sets.

Habitat features such as thalweg depth and bankfull height were measured using NAWQA and EMAP protocols for a stream reach defined for this study as the length of 20 wetted channel widths. Differences between the protocols in measuring bank angle and substrate, for example, sometimes resulted in significant differences in the results.

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