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...
Published in: | Global Biogeochemical Cycles |
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American Geophysical Union
2016
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ftcaltechauth:oai:authors.library.caltech.edu:71310 2023-05-15T13:55:46+02:00 Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean Kemeny, P. C. Weigand, M. A. Zhang, R. Carter, B. R. Karsh, K. L. Fawcett, S. E. Sigman, D. M. 2016-07 application/pdf application/msword https://authors.library.caltech.edu/71310/ https://authors.library.caltech.edu/71310/1/Kemeny_et_al-2016-Global_Biogeochemical_Cycles.pdf https://authors.library.caltech.edu/71310/2/gbc20435-sup-0001-Supplementary.doc https://resolver.caltech.edu/CaltechAUTHORS:20161020-083251171 en eng American Geophysical Union https://authors.library.caltech.edu/71310/1/Kemeny_et_al-2016-Global_Biogeochemical_Cycles.pdf https://authors.library.caltech.edu/71310/2/gbc20435-sup-0001-Supplementary.doc Kemeny, P. C. and Weigand, M. A. and Zhang, R. and Carter, B. R. and Karsh, K. L. and Fawcett, S. E. and Sigman, D. M. (2016) 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. doi:10.1002/2015GB005350. https://resolver.caltech.edu/CaltechAUTHORS:20161020-083251171 <https://resolver.caltech.edu/CaltechAUTHORS:20161020-083251171> other Article PeerReviewed 2016 ftcaltechauth https://doi.org/10.1002/2015GB005350 2021-11-18T18:39:26Z 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 Caltech Authors (California Institute of Technology) Antarctic Antarctic Ocean Pacific Southern Ocean The Antarctic Global Biogeochemical Cycles 30 7 1069 1085 |
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Open Polar |
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Caltech Authors (California Institute of Technology) |
op_collection_id |
ftcaltechauth |
language |
English |
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, P. C. Weigand, M. A. Zhang, R. Carter, B. R. Karsh, K. L. Fawcett, S. E. Sigman, D. M. |
spellingShingle |
Kemeny, P. C. Weigand, M. A. Zhang, R. Carter, B. R. Karsh, K. L. Fawcett, S. E. Sigman, D. M. Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean |
author_facet |
Kemeny, P. C. Weigand, M. A. Zhang, R. Carter, B. R. Karsh, K. L. Fawcett, S. E. Sigman, D. M. |
author_sort |
Kemeny, P. C. |
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 |
American Geophysical Union |
publishDate |
2016 |
url |
https://authors.library.caltech.edu/71310/ https://authors.library.caltech.edu/71310/1/Kemeny_et_al-2016-Global_Biogeochemical_Cycles.pdf https://authors.library.caltech.edu/71310/2/gbc20435-sup-0001-Supplementary.doc https://resolver.caltech.edu/CaltechAUTHORS:20161020-083251171 |
geographic |
Antarctic Antarctic Ocean Pacific Southern Ocean The Antarctic |
geographic_facet |
Antarctic Antarctic Ocean Pacific Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Antarctic Ocean Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctic Ocean Southern Ocean |
op_relation |
https://authors.library.caltech.edu/71310/1/Kemeny_et_al-2016-Global_Biogeochemical_Cycles.pdf https://authors.library.caltech.edu/71310/2/gbc20435-sup-0001-Supplementary.doc Kemeny, P. C. and Weigand, M. A. and Zhang, R. and Carter, B. R. and Karsh, K. L. and Fawcett, S. E. and Sigman, D. M. (2016) 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. doi:10.1002/2015GB005350. https://resolver.caltech.edu/CaltechAUTHORS:20161020-083251171 <https://resolver.caltech.edu/CaltechAUTHORS:20161020-083251171> |
op_rights |
other |
op_doi |
https://doi.org/10.1002/2015GB005350 |
container_title |
Global Biogeochemical Cycles |
container_volume |
30 |
container_issue |
7 |
container_start_page |
1069 |
op_container_end_page |
1085 |
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1766262599261880320 |