Ecological Responses of Streams to Urbanization: a Review of Results from the U.S. Geological Survey's Urban Streams Studies
Thomas.F. Cuffney
U.S. Geological Survey, North Carolina Water Science Center, 3916 Sunset Ridge Road, Raleigh, North Carolina 27607
Abstract
U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program personnel have been
investigating biological (fish, invertebrates, and algae), chemical (major ions, pesticides, nutrients), and
physical (temperature, stage, discharge, in-stream habitat) responses along gradients of urbanization in 11
major metropolitan areas of the conterminous United States. Results from these studies indicate that
stream biota, water chemistry, and hydrology respond to urbanization in predictable ways, with many
similarities among metropolitan areas that are geologically and climatically different. For example, the
rates at which invertebrate assemblages change along the urban gradient were similar for Birmingham,
AL; Raleigh; NC, Atlanta, GA; Boston, MA; and Salt Lake City, UT.
Invertebrate assemblages exhibited the strongest and most consistent responses to urbanization with
richness and biotic integrity decreasing and average tolerance increasing as urbanization increased. Fish
and algal assemblages also changed as urbanization increased (e.g., decreases in fish biotic integrity,
increases in algal diversity and eutrophic species), but not as frequently nor as strongly as invertebrates.
The mobility of fish, the large number of introduced tolerant species, and the ability of some species to
exploit terrestrial food resources tended to obscure the effects of urbanization. The rapid turnover of
algae made them better indicators of local-scale conditions (e.g., spates) than basin-scale conditions
associated with urbanization. Water chemistry, particularly indices derived from the aggregation of
nutrients and pesticides, increased with increasing urbanization. Changes in all three biological
assemblages, however, typically preceded significant changes in water chemistry. Changes in stream
hydrology (timing and duration of flows) also were frequently associated with increases in urbanization
and changes in biota. Similarities in responses among urban areas and in the environmental factors (e.g.,
amount of developed lands, density of roads) associated with these responses indicate that similar
management and mitigation practices may be effective in metropolitan areas in diverse regions of the
country.
Citation:
Cuffney, T.F., 2006, Ecological responses of streams to urbanization: a review of results from the U.S. Geological Survey's urban streams studies: Proceedings of the National Water-Quality Monitoring Council National Monitoring Conference, May 8-12, 2006, San Jose CA.
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