The effects of watershed development on the structural and functional ecology of forested Piedmont stream benthic communities (Virginia)

Suburban development is the fastest growing form of land use in the United States and suburban nonpoint source (NPS) pollution presents a recognized threat to the health of the nation's waterways. Despite knowledge of the destructive nature of suburban NPS pollution, the influence of various regional characteristics on the ecological responses of stream communities to suburban NPS pollution is poorly understood. Test sites in the current study are located within watersheds in the Piedmont ecoregion that represent varying levels of suburban development. Through the identification and quantification of benthic macroinvertebrates collected from these sites, a diverse array of metrics were evaluated in order to determine the effects of suburban development on the functional processes and taxonomic structure of low-order forested Piedmont stream benthic communities. Metrics that responded consistently to the gradation of suburban development, with minimal response to natural variables, were combined to develop a macroinvertebrate index of biotic integrity (MIBI) that is responsive to the specific changes arising from suburban development of forested watersheds. Information gathered from this assessment of the benthic community was applied to an assessment of the effectiveness of best management practices (BMPs) in the region. Results suggest that the benthic communities of streams draining areas of lower density suburban development may retain some of the characteristics of forested stream benthic communities but that streams draining areas of higher density suburban development have benthic communities that are markedly altered from forested streams. BMPs in the region proved to be ineffective at mitigating the impacts imposed by suburban NPS pollution and some had the additional effect of altering the trophic base of downstream reaches and therefore altering the taxonomic structure of downstream benthic communities.