HR: 11:00h
AN: NB22E-03 INVITED     [Abstracts]
TI: Nitrogen-Sulfur Coupling in Freshwater Sediments: Implications for Nitrate Removal by Wetlands, Lakes and Streams
AU: * Burgin, A J
EM: burginam@msu.edu
AF: Kellogg Biological Station and Michigan State University, 3700 Gull Lake Dr., Hickory Corners, MI 49060
AU: Hamilton, S K
EM: hamilton@kbs.msu.edu
AF: Kellogg Biological Station and Michigan State University, 3700 Gull Lake Dr., Hickory Corners, MI 49060
AB: Nitrate disappearance in sediments is usually assumed to be due to respiratory denitrification, an important process for improving water quality. While performing tracer experiments in aquatic sediments of Michigan, we found that nitrate removal coincided with sulfate production, and that sulfate removal commenced only after nitrate was depleted. Because this activity appears to be biological, we hypothesize that the nitrate removal is due to sulfur oxidizing bacteria that use nitrate to oxidize reduced sulfur forms to sulfate. Sulfur oxidizers do not necessarily denitrify nitrate to dinitrogen, but may instead produce ammonium via a form of dissimilatory nitrate reduction to ammonium (DNRA). Push-pull experiments in streams, lakes and wetlands revealed a persistent pattern of sulfate production during nitrate removal. The data also suggest that nitrate introduction is associated with ammonium production and sulfide removal when compared to controls (bromide introduction only). If this is a form of DNRA, nitrate removed via this pathway would remain in a biologically available form, in contrast to respiratory denitrification. The sulfur-oxidizing pathway of nitrate removal has important implications for water quality by coupling nitrate removal to sulfur cycling.
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly