REDEVELOPMENT OF THE WYOMING STREAM INTEGRITY INDEX (WSII) FOR ASSESSING THE BIOLOGICAL CONDITION OF WADEABLE STREAMS IN WYOMING By Eric G. Hargett 1 and Jeremy R. ZumBerge 2 WYOMING DEPARTMENT OF ENVIRONMENTAL QUALITY WATER QUALITY DIVISION 1Wyoming Department of Environmental Quality - Water Quality Division, Herschler Bldg. 4W, 122 W. 25 th St., Cheyenne, WY 82002 USA 2Wyoming Department of Environmental Quality - Water Quality Division, 1866 S. Sheridan Ave., Sheridan, WY 82801 USA November, 2006 CONTENTS EXECUTIVE SUMMARY ..............................................................................................................................iii INTRODUCTION...........................................................................................................................................1 METHODS AND MATERIALS ......................................................................................................................4 Study Area ................................................................................................................................................................ 4 Site Selection ..............................................................................................................................................5 Macroinvertebrates .....................................................................................................................................6 Chemical and Physical Habitat Data...........................................................................................................6 Site Classification…………………………………………………………………………………………………..7 Metric Selection and Screening ..................................................................................................................9 Metric and Index Scoring ..........................................................................................................................10 Index Evaluation and Validation................................................................................................................10 Temporal Variabiltiy ..................................................................................................................................11 Data Analysis ............................................................................................................................................11 RESULTS....................................................................................................................................................11 Site Classification......................................................................................................................................11 Metric Selection and Screening…………………………………………………………………………..……..16 Index Scoring ............................................................................................................................................17 Index Evaluation and Validation………………………………………………… ………………………….....17 Temporal Variabilty ...................................................................................................................................18 DISCUSSION..............................................................................................................................................18 Classification of Wyoming Streams ........................................................................................................18 Metric Selection.......................................................................................................................................21 Model Performance.................................................................................................................................23 Temporal Variability ................................................................................................................................25 Assessment of Anthropogenic Disturbance............................................................................................25 WSII Limitations ......................................................................................................................................26 Conclusions.............................................................................................................................................27 ACKNOWLEDGMENTS..............................................................................................................................28 REFERENCES............................................................................................................................................29 i TABLES Table 1 – Classification efficiencies for sites used to build the discriminant model and delinate bioregions (1993-1999 dataset) and validation sites (2000-2001 dataset) ..................................................................32 Table 2 – Strengths of three stream classifications for benthic macroinvertebrate assemblages from the 157 reference calibration stations……........................................................................................................33 Table 3 – Pearson product-moment correlations of latitude, longitude, elevation, and watershed area with NMS axes....................................................................................................................................................34 Table 4 – Discrimination efficiencies of the initial 86 metrics for each bioregion and the combined Rockies group…........................................................................................................................................................35 Table 5 – Spearman rank correlations of metric values with environmental variables...............................38 Table 6 – Metrics rejected during the metric screening process by reason. ..............................................40 Table 7 – Final metrics included in the Wyoming Stream Integrity Index (WSII)........................................41 Table 8 – Metrics and scoring criteria for each bioregion...........................................................................42 Table 9 – Mean WSII Scores, p-values, and F-values for comparisons between bioregions for both reference calibration and test samples…....................................................................................................44 Table 10 – Scoring thresholds by narrative criteria for each bioregion for the period of record (1993-2001). ....................................................................................................................................................................45 FIGURES Figure 1 – Location of reference (solid circles) and test (open circles) in relation to major perennial streams in Wyoming ……………………………………………………………………………………………….46 Figure 2 - UPGMA cluster analysis dendrogram that shows the fifteen biologically similar groups derived from the reference calibration dataset……………………………………………………………………………47 Figure 3 – Reference (solid circles) and test (open circles) sites in relation to the bioregions of Wyoming ....................................................................................................................................................................48 Figure 4 – NMS ordination plot of reference calibration site data showing spatial patterns for seven bioregions along axes 1 and 2…. ...............................................................................................................49 Figure 5 – Distribution of Wyoming Stream Integrity Index (WSII) values for reference (R), stressed (S), and test (T) samples for seven bioregions with associated discrimination efficiencies (DE) and 90% confidence intervals (CI) in the insert table…. ............................................................................................50 Figure 6 – Linear regressions of Wyoming Stream Integrity Index (WSII) scores with physicochemical variables......................................................................................................................................................51 Figure 7 – Box and whisker plot distribution of referenc calbiration (R) and reference validation (RV) Wyoming Stream Integrity Index (WSII) scores…………………………………………………………………54 Figure 8 – Distribution of WSII scores by narrative aquatic life use support rating in relation to the new bioregions....................................................................................................................................................55 APPENDICES Appendix A - Operational taxonomic units (OTUs) derived from the reference calibration dataset...........56 Appendix B – WSII scores and narrative ratings for samples by bioregion................................................60 ii EXECUTIVE SUMMARY Over the past six years, the Wyoming Department of Environmental Quality – Water Quality Division (WDEQ/WQD) has invested considerable effort in the development of effective indicators for assessment of biological condition of Wyoming streams. Much of the focus has been on developing and refining a statewide multimetric index (MMI) for Wyoming named the Wyoming Stream Integrity Index (WSII). Originally developed in 2000 and later revised in 2002, the WSII is based on macroinvertebrate community-level attributes or metrics designed to assess the degree to which biological communities are different from that expected to occur under reference or baseline conditions. The WSII is one of several tools the WDEQ/WQD uses to understand