"Linkages between denitrification and organic matter quality, Boulder Creek Watershed, CO"
- Denitrification potential is linked to dissolved organic matter characteristics
- Aerobic metabolism rates provide insight on sediment denitrification potentials
- DOM optical properties may improve predictions of watershed nitrogen removal
the chemical composition of DOM was related to denitrification rates. Laboratory bioassays measured denitrification potentials using the acetylene block technique and carbon mineralization via aerobic bioassays, while organic matter characteristics were evaluated using spectroscopic and fractionation methods. Denitrification potentials under ambient and elevated nitrate concentrations were strongly correlated with aerobic respiration rates and the percent mineralized carbon, suggesting that information about the aerobic metabolism of a system can provide valuable insight regarding the ability of the system to additionally reduce nitrate. Multiple linear regressions (MLR) revealed that under elevated nitrate concentrations denitrification potentials were positively related to the presence of protein-like fluorophores and negatively related to more aromatic and oxidized fractions of the DOM pool. Using chemical characterization of the DOM pool along with carbon and nitrate concentrations approximately 70-78% of the observed variability in denitrification potential under elevated and ambient nitrate conditions, respectively, was explained by MLR. Thus, it seems likely that DOM optical properties could help to improve predictions of nitrate removal in the environment. Finally, fluorescence measurements revealed that bacteria used both protein and humic-like organic molecules during denitrification providing further evidence that larger, more aromatic molecules are not necessarily recalcitrant in the environment.
Received 4 May 2011; accepted 1 December 2011.
Citation: (2011), Linkages between denitrification and organic matter quality, Boulder Creek Watershed, CO, J. Geophys. Res., doi:10.1029/2011JG001749, in press.