HR: 0800h
AN: B11B-0146    [Abstracts]
TI: Effects of Urbanization on the Condition of Streams in the Piedmont of North Carolina: Responses of Benthic Macroinvertebrate Assemblages
AU: * Cuffney, T F
EM: tcuffney@usgs.gov
AF: U.S. Geological Survey Water Resources Discipline, 3916 Sunset Ridge Rd., Raleigh, NC 27607 United States
AU: Harned, D A
EM: daharned@usgs.gov
AF: U.S. Geological Survey Water Resources Discipline, 3916 Sunset Ridge Rd., Raleigh, NC 27607 United States
AU: McMahon, G
EM: gmcmahon@usgs.gov
AF: U.S. Geological Survey Water Resources Discipline, 3916 Sunset Ridge Rd., Raleigh, NC 27607 United States
AU: Giddings, E M
EM: giddings@usgs.gov
AF: U.S. Geological Survey Water Resources Discipline, 3916 Sunset Ridge Rd., Raleigh, NC 27607 United States
AB: The effects of urbanization on the physical, chemical, and biological characteristics of streams in the North Carolina Piedmont were investigated as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program. Over 1,200 candidate basins (2-3rd order streams) were identified using a 30-m digital elevation model. A multimetric urban intensity index (UII) derived from population, infrastructure, land use, land cover, and socioeconomic factors was used to characterize the degree of urbanization in each basin. Candidate basins were grouped together based on natural features (e.g., ecoregion, elevation, relief, and soil characteristics) and a subset of 30 basins was selected for study on the basis of uniformity in natural features, representation of the urban gradient (i.e., low to high UII), and accessibility. Biological (fish, benthic macroinvertebrates, and algae), physical (stream stage, temperature, and habitat), and chemical (nutrients, pesticides, and major ions) characteristics were measured in each stream and related to changes in the UII. Biological responses were assessed using multivariate (i.e., assemblage ordinations) and multimetric (i.e., assemblage metrics) methods. The relations between invertebrate responses, the UII, and characteristics of urbanization are described in this paper. These relations were examined using correlations and regressions. Invertebrate assemblages exhibited strong responses to the UII based on ordination site scores (Y = -0.013X + 1.613, R$^{2}$ = 0.78, P $<$ 0.001) and assemblage metrics (e.g., EPT richness Y = -0.165X + 17.004, R$^{2}$ = 0.78, P $<$ 0.001 and richness-based tolerance Y= 0.013X + 5.047, R$^{2}$ = 0.75, P $<$ 0.001). The relations between invertebrate responses and UII were linear and did not show any initial resistance to urbanization. Response rates in the North Carolina Piedmont were similar to response rates reported for the Boston, MA (ordination -0.016, EPT richness -0.268, tolerance 0.015), Birmingham, AL (ordination -0.017, EPT richness -0.168, tolerance 0.015), and Salt Lake City, UT (ordination -0.012, EPT richness -0.169, tolerance 0.021) metropolitan areas based on previous NAWQA Program urban gradient studies. The characteristics of urbanization most strongly associated with degradation of invertebrate assemblages were road density, percentage of population in urban areas, density of households, percentage of basin in developed lands, percentage of basin in urban/recreational grasses, percentage of stream buffer in urban land cover, percentage of homes with utility-supplied natural gas, and density of toxic-release inventory sites. Characteristics associated with high-quality invertebrate assemblages were percentage of basin in forest, percentage of basin in agricultural grasslands, percentage of stream buffers in forest, percentage of stream buffers in agricultural grasses, percentage of homes fueled with bottled gas, and percentage of owner-occupied homes. These driving factors were similar to the factors that were important in NAWQA Program urban gradient studies conducted in Boston, Birmingham, and Salt Lake City indicating a strong commonality in urban effects across the US.
UR: http://nc.water.usgs.gov/albe/General/ulug/index.html
DE: 4804 Benthic processes/benthos
DE: 4857 Pollution
DE: 4239 Limnology
DE: 1803 Anthropogenic effects
DE: 1871 Surface water quality
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting