Heterogeneity in urbanization-induced stream ecosystem degradation between two physiographic regions of the Mid-Atlantic United States

Watershed urbanization severely degrades the ecological integrity of streams. However, the degree of impact along gradients of urban development may not be uniform among geoclimatic settings. We present evidence of heterogeneity in stream ecosystem responses to urbanization between the Coastal Plain and Piedmont physiographic provinces of the Mid-Atlantic United States. Sensitive fish and macroinvertebrate taxa undergo population reduction or extirpation at lower levels of catchment urbanization in Coastal Plain streams relative to those of the Piedmont. Hydrologic analyses revealed that flood frequency and severity are relatively low in rural watersheds, yet more impacted by impervious surfaces, in Coastal Plain streams. Chemical assessments demonstrated comprehensive differences between provinces in rural streams but uniform degradation along urban gradients. Conversely, Piedmont stream temperatures, benthic sediment structure, and particle transport and deposition are relatively more impacted by impervious surfaces. Our findings highlight the relatively acute vulnerability to urbanization in Piedmont stream ecosystems and identify potential mechanistic causes that render Coastal Plain streams more resilient. Further, our results demonstrate the need to consider geoclimatic context when assessing all stream ecosystem responses to land use stressors.