In:
Biogeosciences, Copernicus GmbH, Vol. 17, No. 8 ( 2020-04-22), p. 2263-2287
Abstract:
Abstract. Oxygen-deficient zones (ODZs) are major sites of net natural
nitrous oxide (N2O) production and emissions. In order to understand
changes in the magnitude of N2O production in response to global
change, knowledge on the individual contributions of the major microbial
pathways (nitrification and denitrification) to N2O production and
their regulation is needed. In the ODZ in the coastal area off Peru, the
sensitivity of N2O production to oxygen and organic matter was
investigated using 15N tracer experiments in combination with quantitative PCR (qPCR) and
microarray analysis of total and active functional genes targeting archaeal amoA
and nirS as marker genes for nitrification and denitrification, respectively.
Denitrification was responsible for the highest N2O production with a
mean of 8.7 nmol L−1 d−1 but up to 118±27.8 nmol L−1 d−1 just below the oxic–anoxic interface. The highest N2O production
from ammonium oxidation (AO) of 0.16±0.003 nmol L−1 d−1
occurred in the upper oxycline at O2 concentrations of 10–30 µmol L−1 which coincided with the highest archaeal amoA transcripts/genes.
Hybrid N2O formation (i.e., N2O with one N atom from NH4+
and the other from other substrates such as NO2-) was the dominant
species, comprising 70 %–85 % of total produced N2O from
NH4+, regardless of the ammonium oxidation rate or O2
concentrations. Oxygen responses of N2O production varied with
substrate, but production and yields were generally highest below 10 µmol L−1 O2. Particulate organic matter additions increased
N2O production by denitrification up to 5-fold, suggesting increased
N2O production during times of high particulate organic matter export.
High N2O yields of 2.1 % from AO were measured, but the overall
contribution by AO to N2O production was still an order of magnitude
lower than that of denitrification. Hence, these findings show that
denitrification is the most important N2O production process in low-oxygen conditions fueled by organic carbon supply, which implies a positive
feedback of the total oceanic N2O sources in response to increasing
oceanic deoxygenation.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-17-2263-2020
DOI:
10.5194/bg-17-2263-2020-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2158181-2
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