Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions
This paper presents whole water column data for nitrate N, O isotopic composition for the Kerguelen Plateau area and the basin extending east of Heard Island, aiming at understanding the N-cycling in this naturally iron fertilized area that is characterized by large re-current phytoplankton blooms....
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Copernicus Gesellschaft Mbh
2015
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Online Access: | https://doi.org/10.5194/bg-12-1459-2015 https://archimer.ifremer.fr/doc/00260/37085/35584.pdf https://archimer.ifremer.fr/doc/00260/37085/73105.pdf https://archimer.ifremer.fr/doc/00260/37085/ |
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fttriple:oai:gotriple.eu:10670/1.tvyhd8 2023-05-15T16:33:56+02:00 Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions Dehairs, F. Fripiat, F. Cavagna, A. -j. Trull, T.w. Fernandez, C. Davies, D. Roukaerts, A. Fonseca Batista, D. Planchon, F. Elskens, M. 2015-03-05 https://doi.org/10.5194/bg-12-1459-2015 https://archimer.ifremer.fr/doc/00260/37085/35584.pdf https://archimer.ifremer.fr/doc/00260/37085/73105.pdf https://archimer.ifremer.fr/doc/00260/37085/ en eng Copernicus Gesellschaft Mbh doi:10.5194/bg-12-1459-2015 10670/1.tvyhd8 https://archimer.ifremer.fr/doc/00260/37085/35584.pdf https://archimer.ifremer.fr/doc/00260/37085/73105.pdf https://archimer.ifremer.fr/doc/00260/37085/ lic_creative-commons other Archimer, archive institutionnelle de l'Ifremer Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2015-03-05 , Vol. 12 , N. 5 , P. 1459-1482 envir geo Text https://vocabularies.coar-repositories.org/resource_types/c_18cf/ 2015 fttriple https://doi.org/10.5194/bg-12-1459-2015 2023-01-22T17:57:10Z This paper presents whole water column data for nitrate N, O isotopic composition for the Kerguelen Plateau area and the basin extending east of Heard Island, aiming at understanding the N-cycling in this naturally iron fertilized area that is characterized by large re-current phytoplankton blooms. The KEOPS 2 expedition (October-November 2011) took place in spring season and complements knowledge gathered during an earlier summer expedition to the same area (KEOPS 1, February-March 2005). As noted by others a remarkable condition of the system is the moderate consumption of nitrate over the season (nitrate remains >20 mu M) while silicic acid becomes depleted, suggesting significant recycling of nitrogen. Nitrate isotopic signatures in the upper water column do mimic this condition, with surprising overlap of spring and summer regressions of delta O-18(NO3) vs. delta N-15(NO3) isotopic compositions. These regressions obey rather closely the (18)epsilon/(15)epsilon discrimination expected for nitrate uptake ((18)epsilon/(15)epsilon = 1), but regression slopes as large as 1.6 were observed for the mixed layer above the Kerguelen Plateau. A preliminarily mass balance calculation for the early bloom period points toward significant nitrification occurring in the mixed layer and which may be equivalent to up to 47% of nitrate uptake above the Kerguelen Plateau. A further finding concerns deep ocean low delta O-18(NO3) values (<2%) underlying high chlorophyll waters at the Polar Front Zone and which cannot be explained by remineralization and nitrification of the local particulate nitrogen flux, which is too small in magnitude. However, the studied area is characterized by a complex recirculation pattern that would keep deep waters in the area and could impose a seasonally integrated signature of surface water processes on the deep waters. Text Heard Island Southern Ocean Unknown Heard Island Kerguelen Southern Ocean Biogeosciences 12 5 1459 1482 |
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fttriple |
language |
English |
topic |
envir geo |
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envir geo Dehairs, F. Fripiat, F. Cavagna, A. -j. Trull, T.w. Fernandez, C. Davies, D. Roukaerts, A. Fonseca Batista, D. Planchon, F. Elskens, M. Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions |
topic_facet |
envir geo |
description |
This paper presents whole water column data for nitrate N, O isotopic composition for the Kerguelen Plateau area and the basin extending east of Heard Island, aiming at understanding the N-cycling in this naturally iron fertilized area that is characterized by large re-current phytoplankton blooms. The KEOPS 2 expedition (October-November 2011) took place in spring season and complements knowledge gathered during an earlier summer expedition to the same area (KEOPS 1, February-March 2005). As noted by others a remarkable condition of the system is the moderate consumption of nitrate over the season (nitrate remains >20 mu M) while silicic acid becomes depleted, suggesting significant recycling of nitrogen. Nitrate isotopic signatures in the upper water column do mimic this condition, with surprising overlap of spring and summer regressions of delta O-18(NO3) vs. delta N-15(NO3) isotopic compositions. These regressions obey rather closely the (18)epsilon/(15)epsilon discrimination expected for nitrate uptake ((18)epsilon/(15)epsilon = 1), but regression slopes as large as 1.6 were observed for the mixed layer above the Kerguelen Plateau. A preliminarily mass balance calculation for the early bloom period points toward significant nitrification occurring in the mixed layer and which may be equivalent to up to 47% of nitrate uptake above the Kerguelen Plateau. A further finding concerns deep ocean low delta O-18(NO3) values (<2%) underlying high chlorophyll waters at the Polar Front Zone and which cannot be explained by remineralization and nitrification of the local particulate nitrogen flux, which is too small in magnitude. However, the studied area is characterized by a complex recirculation pattern that would keep deep waters in the area and could impose a seasonally integrated signature of surface water processes on the deep waters. |
format |
Text |
author |
Dehairs, F. Fripiat, F. Cavagna, A. -j. Trull, T.w. Fernandez, C. Davies, D. Roukaerts, A. Fonseca Batista, D. Planchon, F. Elskens, M. |
author_facet |
Dehairs, F. Fripiat, F. Cavagna, A. -j. Trull, T.w. Fernandez, C. Davies, D. Roukaerts, A. Fonseca Batista, D. Planchon, F. Elskens, M. |
author_sort |
Dehairs, F. |
title |
Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions |
title_short |
Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions |
title_full |
Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions |
title_fullStr |
Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions |
title_full_unstemmed |
Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions |
title_sort |
nitrogen cycling in the southern ocean kerguelen plateau area: evidence for significant surface nitrification from nitrate isotopic compositions |
publisher |
Copernicus Gesellschaft Mbh |
publishDate |
2015 |
url |
https://doi.org/10.5194/bg-12-1459-2015 https://archimer.ifremer.fr/doc/00260/37085/35584.pdf https://archimer.ifremer.fr/doc/00260/37085/73105.pdf https://archimer.ifremer.fr/doc/00260/37085/ |
geographic |
Heard Island Kerguelen Southern Ocean |
geographic_facet |
Heard Island Kerguelen Southern Ocean |
genre |
Heard Island Southern Ocean |
genre_facet |
Heard Island Southern Ocean |
op_source |
Archimer, archive institutionnelle de l'Ifremer Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2015-03-05 , Vol. 12 , N. 5 , P. 1459-1482 |
op_relation |
doi:10.5194/bg-12-1459-2015 10670/1.tvyhd8 https://archimer.ifremer.fr/doc/00260/37085/35584.pdf https://archimer.ifremer.fr/doc/00260/37085/73105.pdf https://archimer.ifremer.fr/doc/00260/37085/ |
op_rights |
lic_creative-commons other |
op_doi |
https://doi.org/10.5194/bg-12-1459-2015 |
container_title |
Biogeosciences |
container_volume |
12 |
container_issue |
5 |
container_start_page |
1459 |
op_container_end_page |
1482 |
_version_ |
1766023685732302848 |