EFFECTS OF RIPARIAN STATUS ON BENTHIC MACROINVERTEBRATE ASSEMBLAGES ALONG AN URBAN GRADIENT IN SOUTHEASTERN PENNSYLVANIA, USA

B. D. Marshall^1,2, T. E. Johnson¹, and W. C. Hession^1,3. ¹Patrick Center for Environmental Research, The Academy of Natural Sciences, Philadelphia, PA 19103, ²Current Address: Department of Ecology, Montana State University, Bozeman, MT 59717, ³Current Address: Department of Civil and Environmental Eng. , University of Vermont, Burlington, VT 05405

Reforestation is a commonly used tactic to restore the biotic integrity of streams in the eastern United States because the function of small streams is intimately associated with the condition of riparian forests. The effectiveness of riparian restoration has been demonstrated for streams in agricultural landscapes and to alleviate impacts associated with timber harvest. Although the effectiveness of this effort has not been evaluated for streams impacted by urbanization, planting riparian vegetation is often a key aspect of restoration efforts for urban streams. To evaluate the effects of reforestation on benthic macroinvertebrate assemblages, we quantitatively sampled two reaches (forested and open) on each of 14 streams along an urban gradient. We compared benthic macroinvertebrate assemblages using metrics, community similarity measures, and biomass. Measures were compared using regression analysis to describe the relationship of each measure to the amount of urbanization in each watershed. We used analysis of covariance to describe differences in regression parameters for forested and open reaches. Biological metrics generally responded very rapidly to urbanization, but differences in riparian status where not significant. However, community similarity measures showed that as urbanization increased, similarity of assemblages increased. Preliminary results of functional feeding group biomass were inconclusive.