Publication - National Water-Quality Assessment Program
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Samples of benthic macroinvertebrates were collected side-by-side from riffles at 12 stream sites in Wyoming, Colorado, and Montana during 2000-2001, following protocols established by the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program and the U.S. Environmental Protection Agency Environmental Monitoring and Assessment Program (EMAP). Samples from riffles were collected following NAWQA protocols, using a sampler with 425-micron net mesh-opening size from a total area of 1.25 m2 per sample in multiple riffles. Samples also were collected following EMAP protocols, using a sampler with 500-micron net mesh-opening size from a total area of 0.72 m2 per sample in multiple riffles. The taxonomic identification and enumeration of the samples followed procedures established for each program. Benthic macroinvertebrate community structure was compared between the data sets using individual metrics, a multimetric index, and multivariate analysis.
Comparisons between the macroinvertebrate community structures were made after sequentially adjusting both data sets for: (1) ambiguous taxa, (2) taxonomic inconsistencies, and (3) differences in laboratory subsampling. After removal of ambiguous taxa, pair-wise differences in total taxa richness and Ephemeroptera taxa richness were statistically significant (p < 0.05). Differences between the data sets generally were not significant for richness of other taxa, tolerant taxa, semi-voltine taxa, functional feeding groups, diversity, and dominance. Sample scores calculated using the Wyoming Stream Integrity Index were not significantly different between the two data sets. After reconciling both data sets for taxonomic inconsistencies, total taxa richness and Ephemeroptera taxa richness remained significantly different between the data sets. After adjusting the data for differences in laboratory subsampling, the differences in taxa richness were no longer significant. Bray-Curtis similarity coefficients and non-metric multi-dimensional scaling were used to examine macroinvertebrate community structure. Similarity in community structure between sites was affected to a greater extent by taxa reconciliation than by adjustment for subsampling.
Purpose and Scope
Description of the Study Area
Comparison of Macroinvertebrate Community Structure
Initial Data Set
Adjustment for Subsampling
Synopsis of Comparisons
Summary and Conclusions
1. Map showing locations of sampling sites, NAWQA-EMAP comparative study, Wyoming, Colorado, and Montana, 2000-2001.
2–4. Graphs showing:
2. Selected metrics of macroinvertebrate community structure and scores from the Wyoming Stream Integrity Index for 12 paired NAWQA and EMAP samples, comparative study, Wyoming, Colorado, and Montana, 2000-2001.
3. Total taxa richness in NAWQA and EMAP data sets after taxa reconciliation and subsampling, comparative study, Wyoming, Colorado, and Montana, 2000-2001.
4. Non-metric multi-dimensional plots of macroinvertebrate community structure,comparative study, Wyoming, Colorado, and Montana, 2000-2001.
1. Macroinvertebrate sampling sites in comparative study, Wyoming, Colorado, and Montana, 2000-2001.
2. Metrics used in the Wyoming Stream Integrity Index to compute scores for mountain and non-mountain streams, comparative study, Wyoming, Colorado, and Montana, 2000-2001.
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