Denitrification Associated with Stream Periphyton: Chamber Estimates from Undisrupted Communities1
- J. H. Duff,
- F. J. Triska and
- R. S. Oremland2
Undisrupted periphyton communities from a N-rich (NO3− = 63 µmol L−1) and pristine (NO3− = 2.9 µmol L−1) stream were assayed for denitrifying activity (acetylene-blockage technique) in 40-L chambers incubated at in situ temperature and nutrient concentrations. Nitrous oxide formation associated with periphyton from the N-rich stream was immediate and linear (52.1 µmol N2O m−2 h−1) in the dark, anaerobic chamber (50 kPa C2H2). In the corresponding light, aerobic chamber (50 kPa C2H2), N2O production was inhibited by 82% (9.3 µmol N2O m−2 h−1). Nitrous oxide formation was not associated with periphyton from the pristine stream incubated in situ, either with or without NO3− amendment.
Denitrification estimates made with undisrupted periphyton communities at in situ temperature and nutrient concentrations (40-L chambers) were less variable than estimates made with periphyton “scrapings” in small flasks (room temperature). The calculated diel periphyton-associated denitrification rate based on a 14-h light-10-h dark day was 651 µmol N2O m−2 d−1. The data suggest denitrification within periphyton mats may contribute toward removal of NO3− from N-rich fluvial environments.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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