Effects of urbanization on instream habitat and fish assemblages in the chattanooga metropolitan area, Tennessee-Georgia

摘要

Twenty-one stream sites in the Ridge and Valley ecoregion of Tennessee and Georgia were studied in 2008 to evaluate the effects of watershed urbanization on instream environmental parameters and fish assemblages. I also investigated changes in urbanization and stream conditions at 10 sites over a 10-year period (1998-2008). Electrofishing yielded 12,329 fish, composed of 38 species from eight families. Urbanization in the study watersheds was measured (using ArcGIS 9.3; released June, 2008) by calculating the building density and percent urban land use. Correlation analysis revealed that more urbanized watersheds were characterized by increased proportions of fine sediments and pool areas, coupled with reduced variation in channel complexity. Urbanized watersheds exhibited declines in biotic integrity, species diversity, richness and evenness. Watershed urbanization was also correlate d with declines of the proportions of cyprinids and percids, as well as an increase in centrarchid proportions. Findings from this study suggest that urban development has induced adverse transformations in both habitat quality and biotic health in Chattanooga area streams. Percent urban land use was found to be a stronger correlate of stream conditions than building density. Results from the 10-year comparison suggest that urban development induces stream habitat degradation at both low and moderate levels of urbanization, although the type and magnitude of degradation may be related to growth rates and specific stages of urban development. Intensive degradation of fish communities likely occurs in watersheds during periods of accelerated urbanization.