2007 BES Annual Meeting Presentation and Poster Abstracts
Particulate and Dissolved Organic Matter in Urban Streams: Fluxes, Spatial Patterns and the Effects of Urban Hydrology along the Urban Stream Continuum.
Co-Authors: Kenneth Belt, Sujay Kaushal, Christopher Swan, Richard Pouyat, Peter Groffman
Abstract: The large drainage densities of urban catchments facilitate OM (organic matter) transport, creating a "gutter subsidy" to streams that likely dwarfs riparian input. Catchments with roads and other impervious features therefore present an "Urban Stream Continuum" (USC) in which these upland features increasingly determine dissolved (DOC) or Particulate (POM) carbon fluxes to streams. We discuss a conceptual framework for the USC and describe several years of data for 16 streams of the BES LTER network. Storm and dry weather DOC, TSS (total suspended solids), and FPOM (fine particulate OM) revealed high temporal variance, with high OM fluxes and concentrations. Spatially, OM concentrations were greater in the catchments with the least and most dense storm drainage networks (highest levels in the densest catchments.) This may be due to gutter mediated inputs and associated increases in stream productivity such that greater fluxes occur even during base flow. Hydrologic drivers exerted great influence on both DOC and FPOM/TSS concentrations, with storm runoff flows producing very high concentrations and lower FPOM/TSS ratios. Even post (surface) runoff flows produced high OM levels, suggesting that transport is influenced by post storm groundwater flows and channel storage. Conversely, drought produced low DOC concentrations, indicating a flow threshold that these source areas that is possibly facilitated by buried stream systems. These results suggest that the altered drainage pathways and strong terrestrial-aquatic linkages of urban catchments may combine to produce high OM fluxes. This has important implications for aquatic food webs and productivity, for associated pollutants, and the management of these inputs.