Baltimore Ecosystem Study Institute of Ecosystem Studies

2010 BES Annual Meeting Presentation and Poster Abstracts

Relative importance of organic C sources for denitrification in hyporheic zones of forested, unrestored, and restored streams
Newcomer, Tamara
Co-Authors: Sujay S. Kaushal, Paul M. Mayer, Amy Shields, Elizabeth A. Canuel, Peter M. Groffman, Arthur J. Gold

Abstract: Organic carbon is important in regulating ecosystem function and its source and lability may be impacted by land use and management. We hypothesized that quantity and quality of organic matter would affect denitrification in forested, restored, and unrestored, urban-degraded streams. We examined hyporheic zone denitification potentials associated with various local organic carbon sources in 2 forested, 2 restored, and 2 unrestored streams in the Baltimore LTER and a suburban stream in Kingston, Rhode Island. Hyporheic sediment samples were incubated with different organic carbon treatments (baseflow, stormflow, leaves, grass, and algae). Denitrification enzyme activity assays were measured following 3-day incubations with organic carbon sources and KNO3. Stable isotope signatures and lipid biomarker analysis suggested that terrestrial organic carbon sources in streams varied based on watershed land use patterns and riparian management. ANOVA followed by Tukey’s test revealed that denitrification potential rates were significantly different between algae:(leaves, baseflow, and stormflow) and grass: (leaves, baseflow, and stormflow) (p<0.05). Denitrification potential rates in unrestored streams responded more strongly to grass with a maximum rate of 7,159 ng N g dry soil/hour. Our results suggest that urbanization and vegetation can influence organic carbon quality and the source of organic matter delivered to streams and have substantial potential impacts on ecosystem services such as denitrification. Stream restoration and riparian management should consider the potential differential effects of vegetation on in-stream N processing.