Scientific Investigations Report 2010–5051
This study evaluated the relations between algal, invertebrate, and fish assemblages and physical environmental characteristics of streams at the reach, segment, and watershed scale in agricultural settings in the Midwest. The 86 stream sites selected for study were in predominantly agricultural watersheds sampled as part of the U.S. Geological Survey’s National Water-Quality Assessment Program. Species abundance and over 130 biological metrics were used to determine which aspects of the assemblages were most sensitive to change at the three spatial scales. Digital orthophotograph-based riparian land use/land cover was used for analyses of riparian conditions at the reach and segment scales. The percentage area of different land-use/land-cover types was also determined for each watershed. Out of over 230 environmental characteristics examined, those that best explained variation in the biotic assemblages at each spatial scale include the following: 1) reach: bank vegetative cover, fine silty substrate, and open canopy angle; 2) segment: woody vegetation and cropland in the 250-m riparian buffer, and average length of undisturbed buffer; and 3) watershed: land use/land cover (both total forested and row crop), low-permeability soils, slope, drainage area, and latitude. All three biological assemblages, especially fish, correlated more with land use/land cover and other physical characteristics at the watershed scale than at the reach or segment scales. This study identifies biotic measures that can be used to evaluate potential improvements resulting from agricultural best-management practices and other conservation efforts, as well as evaluate potential impairment from urban development or other disturbances.
First posted September 28, 2010
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Hambrook Berkman, J.A., Scudder, B.C., Lutz, M.A., and Harris, M.A., 2010, Evaluation of aquatic biota in relation to environmental characteristics measured at multiple scales in agricultural streams of the Midwest, 1993–2004: U.S. Geological Survey Scientific Investigations Report, 2010–5051, 24 p.
Purpose and Scope
Relations between Biological Assemblages, Biological Metrics, and Environmental Characteristics
Spatial and Temporal Variability of Biological Metrics
Relations between Biota and Multiscale Environmental Characteristics
Biological Assemblages with Environmental Characteristics
At the Reach Scale
At the Segment Scale
At the Watershed Scale
Biological Metrics with Environmental Characteristics
Spatial and Temporal Variability of Metrics
Discussion of Findings and Comparison with Other Studies
Implications for the Use of Aquatic Biota in Evaluations of Agricultural Best-Management Practices
Summary and Conclusions