Paul Freeman, Effects Of Watershed Land Use On The Benthic Macroinvertebrate Assemblages In Ridge And Valley Streams In Chattanooga, Tennessee
Faculty Chair: Dr. Mark Schorr
A total of 20 sites in five Ridge and Valley streams located in Chattanooga, Tennessee were sampled May 8, 1998 to June 18, 1998 using quantitative and qualitative macro invertebrate sampling techniques. All streams sampled were part of the Tennessee River drainage system and eventually contribute to Nickajack Reservoir. The 20 sites were second- to fourth-order streams with drainage areas of 3.8 to 46.9 km2 and elevations of 195 to 232 m. Sites with different percentages of agricultural, urbanized and forested land use were selected to best evaluate the resulting impacts of urbanization and other anthropogenic activities on the invertebrate community and over all water quality.
Characterizations of stream sites were made using indices commonly used to qualitatively compare invertebrate assemblages including the total number of taxa (richness), and the number of families of insects belonging to the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT taxa richness). Qualitative sampling efforts collected 76 family level taxa with individual sites ranging from 21 to 41 and a mean of 29.8 (SD = 5.1). The EPT taxa index resulted in site scores ranging from 3 (poor) to 16 (good) with a mean of 7.4 (fair) (SD = 3.7). This wide range of scores indicates portions of the local watersheds were healthy while other portions were quite degraded. Differences in stream sites were explored more fully by quantitative analyses of 22,613 invertebrates collected in 79 Hess samples. Field collections showed marked differences in taxa richness, mean abundance, and percent taxa composition across study sites. Habitat conditions and benthic indices varied between sites within study streams. This study revealed relationships between benthic indices and water quality, habitat conditions and land use. Relationships between watershed land use and instream substrate (cobble and fine sediments) were evident. Portions of local watersheds were quite degraded while other sections approached "reference-stream" quality. The sub-watersheds of Black Creek, Mountain Creek and Ninemile Branch show more degradation of water quality and habitat in the lower reaches than in the upper, less developed portions. The upper Black Creek study site indicated the best assemblage of invertebrates in the study, while Friar Branch and the lower Ninemile Branch sites showed the poorest, most degraded communities. Significant correlations (P<0.1) observed in this study underscore the negative effects of agricultural and urban land use on invertebrate assemblages and habitat quality in streams.