2023 Early Hearing Detection & Intervention Conference
March 5-7, 2023 • Cincinnati, OH
6/06/2017 | 11:15 AM - 11:30 AM | DO NITROGEN FIXATION AND DENITRIFICATION CO-OCCUR ACROSS A GRADIENT OF STREAM N CONCENTRATIONS IN A WESTERN WATERSHED? | 306A
DO NITROGEN FIXATION AND DENITRIFICATION CO-OCCUR ACROSS A GRADIENT OF STREAM N CONCENTRATIONS IN A WESTERN WATERSHED?
It is frequently assumed that N2 fixation and denitrification do not co-occur in streams because they are favored under different concentrations of reactive nitrogen. Yet, this assumption has not been evaluated because both processes are rarely quantified in the same stream. We asked if these processes could co-exist by measuring rates of N2 fixation using acetylene reduction, denitrification using acetylene block, and net N2 flux using membrane inlet mass spectrometry on rocks and sediment in 8 southeastern Idaho streams encompassing a dissolved inorganic nitrogen (DIN) gradient of 6-615 µg/L. N2 fixation and denitrification rates were 0-218 and 0.41-5.66 µg N/m2/hr, respectively. The highest N2 fixation rates occurred in streams with the lowest DIN concentrations, and denitrification rates generally increased with increasing DIN. However, low rates of both processes occurred across the full gradient, suggesting DIN concentration alone cannot predict their occurrence. In two streams we made measurements of high spatial resolution and found high rates of both processes occurred in close proximity to one another, suggesting that small-scale variation in substrate and environmental conditions facilitates the co-occurrence of these processes.
- C10 Biogeochemistry
- C10 Biogeochemistry
- C10 Biogeochemistry
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Presenters/Authors
Erin Eberhard
(), Michigan Technological University , ekeberha@mtu.edu;
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Amy Marcarelli
(), Michigan Technological University, ammarcar@mtu.edu;
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Colden Baxter
(), Idaho State University, baxtcold@isu.edu;
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