Institute of Ecosystem Studies

2007 BES Annual Meeting Presentation and Poster Abstracts

Patchiness in Microbial Nitrogen Cycling Processes in Forested and Urban Streams
Harrison, Melanie
Co-Authors: M.D.Harrison¹ and P.Groffman², ¹Univeristy of Maryland Baltimore County, Baltimore, MD and ²Institute of Ecosystem Studies, Millbrook, NY
Abstract: The health of our waters is essential for sustainable life on earth. Yet, ensuring healthy streams is especially difficult in urban areas where population shifts and land use changes greatly affect ecosystem functioning and services. Urban streams are typically degraded, characterized by highly incised channels, eroded stream banks, disconnected floodplains, and high peak flows. Of particular concern is increasing nitrogen loadings that threaten stream health, and as a consequence, the healthy functioning of our coastal oceans and estuaries. Our main goal is to identify if stream restoration gives a functional payoff that is, high anaerobic denitrification activity (DEA) in stream features resulting in the removal of nitrate. In this study, we measured a suite of microbial variables (denitrification potential, net nitrification, organic matter content and soil moisture), in urban, rural, and suburban streams features in the Baltimore Metropolitan Area. Results show that DEA rates were highly correlated with carbon and nitrogen -related variables. There were no significant differences in DEA potential across all sites for pool-riffle features however, nitrification rates were much higher in suburban streams. Organic debris dams were sampled in only reference streams and as expected, pristine (reference) streams have significantly higher denitrification activity than restored or degraded streams. This suggest that the incorporation of organic debris structures in urban stream restoration projects could create potential "hotspots" for denitrification in urban streams.