HR: 1330h
AN: NB33K-07    [Abstracts]
TI: Carbon Limited Heterotrophic Activity in an Urban Stream
AU: * Hassett, B
EM: bhassett@umd.edu
AF: University of Maryland, Department of Entomology, College Park, MD 20742 United States
AU: Bernhardt, E
AF: Duke University, Department of Biology, Durham, NC 27708 United States
AU: Palmer, M
AF: University of Maryland, Department of Entomology, College Park, MD 20742 United States
AB: Urban streams are characterized by flashy hydrographs, heavily incised channels, and scoured bed materials. Because of frequent scour, benthic organic matter in urban streams tends to be extremely low relative to nonurban streams. Recent research has related low organic matter availability to low rates of nitrogen uptake. We hypothesized that urban streams are carbon limited, and tested this hypothesis by adding a pulse of labile carbon (as potassium acetate) to the Stewart April tributary of Paint Branch, which drains a heavily urbanized watershed 73% impervious cover) in the suburbs of Washington, D.C. We predicted that the magnitude of the carbon effect on stream metabolism and N processing would be reduced as a result of litter inputs, and compared the stream response before and after peak litterfall. Adding labile dissolved organic carbon to the stream immediately increased metabolism in the stream channel during both additions, but this increase in heterotrophic activity did not lead to reductions in dissolved inorganic nitrogen concentrations. This indicates that while heterotrophs in this stream are carbon limited, the microbial community was not able to respond quickly enough to the pulse addition to appreciably reduce DIN concentrations in this eutrophic stream.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly