Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean
In the Southern Ocean, the nitrogen (N) isotopes of organic matter and the N and oxygen (O) isotopes of nitrate (NO 3 − ) have been used to investigate NO 3 − assimilation and N cycling in the summertime period of phytoplankton growth, both today and in the past. However, recent studies indicate the...
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ftunivtasecite:oai:ecite.utas.edu.au:114803 2023-05-15T13:49:03+02:00 Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean Kemeny, PC Weigand, MA Zhang, R Carter, BR Karsh, KL Fawcett, SE Sigman, DM 2016 application/pdf https://doi.org/10.1002/2015GB005350 http://ecite.utas.edu.au/114803 en eng Amer Geophysical Union http://ecite.utas.edu.au/114803/1/114803 final.pdf http://dx.doi.org/10.1002/2015GB005350 Kemeny, PC and Weigand, MA and Zhang, R and Carter, BR and Karsh, KL and Fawcett, SE and Sigman, DM, Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean, Global Biogeochemical Cycles, 30, (7) pp. 1069-1085. ISSN 0886-6236 (2016) [Refereed Article] http://ecite.utas.edu.au/114803 Earth Sciences Oceanography Chemical Oceanography Refereed Article PeerReviewed 2016 ftunivtasecite https://doi.org/10.1002/2015GB005350 2019-12-13T22:14:37Z In the Southern Ocean, the nitrogen (N) isotopes of organic matter and the N and oxygen (O) isotopes of nitrate (NO 3 − ) have been used to investigate NO 3 − assimilation and N cycling in the summertime period of phytoplankton growth, both today and in the past. However, recent studies indicate the significance of processes in other seasons for producing the annual cycle of N isotope changes. This study explores the impact of fall conditions on the 15 N/ 14 N (δ 15 N) and 18 O/ 16 O (δ 18 O) of NO 3 − and nitrite (NO 2 − ) in the Pacific Antarctic Zone using depth profiles from late summer/fall of 2014. In the mixed layer, the δ 15 N and δ 18 O of NO 3 − + NO 2 − increase roughly equally, as expected for NO 3 − assimilation; however, the δ 15 N of NO 3 − -only (measured after NO 2 − removal) increases more than does NO 3 − -only δ 18 O. Differencing indicates that NO 2 − has an extremely low δ 15 N, often < −70 versus air. These observations are consistent with the expression of an equilibrium N isotope effect between NO 3 − and NO 2 − , likely due to enzymatic NO 3 − -NO 2 − interconversion. Specifically, we propose reversibility of the nitrite oxidoreductase (NXR) enzyme of nitrite oxidizers that, having been entrained from the subsurface during late summer mixed layer deepening, are inhibited by light. Our interpretation suggests a role for NO 3 − -NO 2 − interconversion where nitrifiers are transported into environments that discourage NO 2 − oxidation. This may apply to surface regions with upwelling, such as the summertime Antarctic. It may also apply to oxygen-deficient zones, where NXR-catalyzed interconversion may explain previously reported evidence of NO 2 − oxidation. Article in Journal/Newspaper Antarc* Antarctic Antarctic Ocean Southern Ocean eCite UTAS (University of Tasmania) Antarctic Southern Ocean The Antarctic Pacific Antarctic Ocean Global Biogeochemical Cycles 30 7 1069 1085 |
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eCite UTAS (University of Tasmania) |
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ftunivtasecite |
language |
English |
topic |
Earth Sciences Oceanography Chemical Oceanography |
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Earth Sciences Oceanography Chemical Oceanography Kemeny, PC Weigand, MA Zhang, R Carter, BR Karsh, KL Fawcett, SE Sigman, DM Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean |
topic_facet |
Earth Sciences Oceanography Chemical Oceanography |
description |
In the Southern Ocean, the nitrogen (N) isotopes of organic matter and the N and oxygen (O) isotopes of nitrate (NO 3 − ) have been used to investigate NO 3 − assimilation and N cycling in the summertime period of phytoplankton growth, both today and in the past. However, recent studies indicate the significance of processes in other seasons for producing the annual cycle of N isotope changes. This study explores the impact of fall conditions on the 15 N/ 14 N (δ 15 N) and 18 O/ 16 O (δ 18 O) of NO 3 − and nitrite (NO 2 − ) in the Pacific Antarctic Zone using depth profiles from late summer/fall of 2014. In the mixed layer, the δ 15 N and δ 18 O of NO 3 − + NO 2 − increase roughly equally, as expected for NO 3 − assimilation; however, the δ 15 N of NO 3 − -only (measured after NO 2 − removal) increases more than does NO 3 − -only δ 18 O. Differencing indicates that NO 2 − has an extremely low δ 15 N, often < −70 versus air. These observations are consistent with the expression of an equilibrium N isotope effect between NO 3 − and NO 2 − , likely due to enzymatic NO 3 − -NO 2 − interconversion. Specifically, we propose reversibility of the nitrite oxidoreductase (NXR) enzyme of nitrite oxidizers that, having been entrained from the subsurface during late summer mixed layer deepening, are inhibited by light. Our interpretation suggests a role for NO 3 − -NO 2 − interconversion where nitrifiers are transported into environments that discourage NO 2 − oxidation. This may apply to surface regions with upwelling, such as the summertime Antarctic. It may also apply to oxygen-deficient zones, where NXR-catalyzed interconversion may explain previously reported evidence of NO 2 − oxidation. |
format |
Article in Journal/Newspaper |
author |
Kemeny, PC Weigand, MA Zhang, R Carter, BR Karsh, KL Fawcett, SE Sigman, DM |
author_facet |
Kemeny, PC Weigand, MA Zhang, R Carter, BR Karsh, KL Fawcett, SE Sigman, DM |
author_sort |
Kemeny, PC |
title |
Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean |
title_short |
Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean |
title_full |
Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean |
title_fullStr |
Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean |
title_full_unstemmed |
Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean |
title_sort |
enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the antarctic ocean |
publisher |
Amer Geophysical Union |
publishDate |
2016 |
url |
https://doi.org/10.1002/2015GB005350 http://ecite.utas.edu.au/114803 |
geographic |
Antarctic Southern Ocean The Antarctic Pacific Antarctic Ocean |
geographic_facet |
Antarctic Southern Ocean The Antarctic Pacific Antarctic Ocean |
genre |
Antarc* Antarctic Antarctic Ocean Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctic Ocean Southern Ocean |
op_relation |
http://ecite.utas.edu.au/114803/1/114803 final.pdf http://dx.doi.org/10.1002/2015GB005350 Kemeny, PC and Weigand, MA and Zhang, R and Carter, BR and Karsh, KL and Fawcett, SE and Sigman, DM, Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean, Global Biogeochemical Cycles, 30, (7) pp. 1069-1085. ISSN 0886-6236 (2016) [Refereed Article] http://ecite.utas.edu.au/114803 |
op_doi |
https://doi.org/10.1002/2015GB005350 |
container_title |
Global Biogeochemical Cycles |
container_volume |
30 |
container_issue |
7 |
container_start_page |
1069 |
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1085 |
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1766250689820884992 |