Effects of Urbanization on Stream Ecosystems

<em>Abstract.</em>—We evaluated a comprehensive set of natural and land-use attributes that represent the major facets of urban development at fish monitoring sites in the rapidly growing Raleigh-Durham, North Carolina metropolitan area. We used principal component and correlation analysis to obtain a nonredundant subset of variables that extracted most variation in the complete set. With this subset of variables, we assessed the effect of urban growth on fish assemblage structure. We evaluated variation in fish assemblage structure with nonmetric multidimensional scaling (NMDS). We used correlation analysis to identify the most important environmental and landscape variables associated with significant NMDS axes. The second NMDS axis is related to many indices of land-use/landcover change and habitat. Significant correlations with proportion of largest forest patch to total patch size (<em>r </em>= –0.460, <EM>P </EM>< 0.01), diversity of patch types (<em>r </em>= 0.554, <EM>P </EM>< 0.001), and population density (<em>r </em>= 0.385, <EM>P </EM>< 0.05) helped identify NMDS axis 2 as a disturbance gradient. Positive and negative correlations between the abundance of redbreast sunfish <em>Lepomis auritus </em>and bluehead chub <em>Nocomis leptocephalus</em>, respectively, and NMDS axis 2 also were evident. The North Carolina index of biotic integrity and many of its component metrics were highly correlated with urbanization. These results indicate that aquatic ecosystem integrity would be optimized by a comprehensive integrated management strategy that includes the preservation of landscape function by maximizing the conservation of contiguous tracts of forested lands and vegetative cover in watersheds.