Effects of urbanization on habitats and fish communities of Midwestern headwater streams

Cecil Frank Rich, Purdue University

Abstract

Headwater streams have had a history of degradation due to human activities. Although impacts of intensive agriculture on stream health have received more attention, urban expansion into agricultural watersheds has led to an increasing emphasis on better understanding urban stream processes. In the present study 24 stream sites within eight watersheds in central Indiana (USA) representing an agriculture-urban land use gradient were examined to determine trends between urbanization and stream quality and to identify potential physical and biotic indicators of urbanization on fish community change. Current land use and impervious area for the study watersheds were determined by classification of satellite images. Historic streamflow records suggest that increased imperviousness has led to increased runoff and downstream channel instability in the most urbanized watersheds. This study found significant correlations between impervious area, channel morphological change, reduced habitat quality, and the loss of sensitive components of fish communities. Relative to nearby agricultural streams, streams with the highest percentage of watershed imperviousness had increased stream power and bankfull discharge per unit watershed area, loss of in-stream habitat quality (QHEI) and riparian buffer integrity. Significance of relations between environmental variables and fish species traits were assessed using the fourth-corner method, a new permutation technique designed to link traits of species to the habitat characteristics of the locations at which they are found. Urban stream fish communities lacked sensitive species including those highly dependent on the substrate for feeding and reproduction (darters, sculpin and several Cyprinid species; P = 0.001). Associations between urbanization and the fish community identified in this study that were recommended for further development as urbanization indicators include: impervious area, high density urban land cover, forested land cover of the catchment and riparian buffer scales, and new variables of stream power, bankfull discharge per unit watershed area, qualitative habitat index (QHEI), Johnson channel stability index, percent eroded banks, number of darter species, functional fish community measures of reproductive guild, habitat orientation, substrate preference, and tolerance to silt. These results provide insights into the ways in which urbanization impacts stream fish communities and identifies potential tools for monitoring development-related impacts on stream ecosystems.

Degree

Ph.D.

Advisors

Spacie, Purdue University.

Subject Area

Ecology|Forestry

COinS