In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 38 ( 2016-09-20), p. 10601-10606
Abstract:
A major percentage of fixed nitrogen (N) loss in the oceans occurs within nitrite-rich oxygen minimum zones (OMZs) via denitrification and anammox. It remains unclear to what extent ammonium and nitrite oxidation co-occur, either supplying or competing for substrates involved in nitrogen loss in the OMZ core. Assessment of the oxygen (O 2 ) sensitivity of these processes down to the O 2 concentrations present in the OMZ core ( 〈 10 nmol⋅L −1 ) is therefore essential for understanding and modeling nitrogen loss in OMZs. We determined rates of ammonium and nitrite oxidation in the seasonal OMZ off Concepcion, Chile at manipulated O 2 levels between 5 nmol⋅L −1 and 20 μmol⋅L −1 . Rates of both processes were detectable in the low nanomolar range (5–33 nmol⋅L −1 O 2 ), but demonstrated a strong dependence on O 2 concentrations with apparent half-saturation constants ( K m s) of 333 ± 130 nmol⋅L −1 O 2 for ammonium oxidation and 778 ± 168 nmol⋅L −1 O 2 for nitrite oxidation assuming one-component Michaelis–Menten kinetics. Nitrite oxidation rates, however, were better described with a two-component Michaelis–Menten model, indicating a high-affinity component with a K m of just a few nanomolar. As the communities of ammonium and nitrite oxidizers were similar to other OMZs, these kinetics should apply across OMZ systems. The high O 2 affinities imply that ammonium and nitrite oxidation can occur within the OMZ core whenever O 2 is supplied, for example, by episodic intrusions. These processes therefore compete with anammox and denitrification for ammonium and nitrite, thereby exerting an important control over nitrogen loss.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.1600359113
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2016
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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