Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications
Photochemistry of dissolved organic matter (DOM) plays an important role in marine biogeochemical cycles, including the regeneration of inorganic nutrients. DOM photochemistry affects nitrogen cycling by converting bio-refractory dissolved organic nitrogen to labile inorganic nitrogen, mainly ammoni...
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Copernicus Publications
2012
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00024695 2023-05-15T15:40:18+02:00 Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications Xie, H. Bélanger, S. Song, G. Benner, R. Taalba, A. Blais, M. Tremblay, J.-É. Babin, M. 2012-08 electronic https://doi.org/10.5194/bg-9-3047-2012 https://noa.gwlb.de/receive/cop_mods_00024695 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00024650/bg-9-3047-2012.pdf https://bg.copernicus.org/articles/9/3047/2012/bg-9-3047-2012.pdf eng eng Copernicus Publications Biogeosciences -- http://www.bibliothek.uni-regensburg.de/ezeit/?2158181 -- http://www.copernicus.org/EGU/bg/bg.html -- 1726-4189 https://doi.org/10.5194/bg-9-3047-2012 https://noa.gwlb.de/receive/cop_mods_00024695 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00024650/bg-9-3047-2012.pdf https://bg.copernicus.org/articles/9/3047/2012/bg-9-3047-2012.pdf uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2012 ftnonlinearchiv https://doi.org/10.5194/bg-9-3047-2012 2022-02-08T22:50:02Z Photochemistry of dissolved organic matter (DOM) plays an important role in marine biogeochemical cycles, including the regeneration of inorganic nutrients. DOM photochemistry affects nitrogen cycling by converting bio-refractory dissolved organic nitrogen to labile inorganic nitrogen, mainly ammonium (NH4+). During the August 2009 Mackenzie Light and Carbon (MALINA) Program, the absorbed photon-based efficiency spectra of NH4+ photoproduction (i.e. photoammonification) were determined using water samples from the SE Beaufort Sea, including the Mackenzie River estuary, shelf, and Canada Basin. The photoammonification efficiency decreased with increasing wavelength across the ultraviolet and visible regimes and was higher in offshore waters than in shelf and estuarine waters. The efficiency was positively correlated with the molar nitrogen:carbon ratio of DOM and negatively correlated with the absorption coefficient of chromophoric DOM (CDOM). Combined with collateral measurements of CO2 and CO photoproduction, this study revealed a stoichiometry of DOM photochemistry with a CO2 : CO : NH4+ molar ratio of 165 : 11 : 1 in the estuary, 60 : 3 : 1 on the shelf, and 18 : 2 : 1 in the Canada Basin. The NH4+ efficiency spectra, along with solar photon fluxes, CDOM absorption coefficients and sea ice concentrations, were used to model the monthly surface and depth-integrated photoammonification rates in 2009. The summertime (June–August) rates at the surface reached 6.6 nmol l−1 d−1 on the Mackenzie Shelf and 3.7 nmol l−1 d−1 further offshore; the depth-integrated rates were correspondingly 8.8 μmol m−2 d−1 and 11.3 μmol m−2 d−1. The offshore depth-integrated rate in August (8.0 μmol m−2 d−1) was comparable to the missing dissolved inorganic nitrogen (DIN) source required to support the observed primary production in the upper 10-m layer of that area. The yearly NH4+ photoproduction in the entire study area was estimated to be 1.4 × 108 moles, with 85% of it being generated in summer when riverine DIN input is low. Photoammonification could mineralize 4% of the annual dissolved organic nitrogen (DON) exported from the Mackenzie River and provide a DIN source corresponding to 7% of the riverine DIN discharge and 1400 times the riverine NH4+ flux. Under a climate warming-induced ice-free scenario, these quantities could increase correspondingly to 6%, 11%, and 2100 times. Photoammonification is thus a significant nitrogen cycling term and may fuel previously unrecognized autotrophic and heterotrophic production pathways in the surface SE Beaufort Sea. Article in Journal/Newspaper Beaufort Sea canada basin Mackenzie river Mackenzie Shelf Sea ice Niedersächsisches Online-Archiv NOA Canada Mackenzie River Biogeosciences 9 8 3047 3061 |
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Niedersächsisches Online-Archiv NOA |
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English |
topic |
article Verlagsveröffentlichung |
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article Verlagsveröffentlichung Xie, H. Bélanger, S. Song, G. Benner, R. Taalba, A. Blais, M. Tremblay, J.-É. Babin, M. Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications |
topic_facet |
article Verlagsveröffentlichung |
description |
Photochemistry of dissolved organic matter (DOM) plays an important role in marine biogeochemical cycles, including the regeneration of inorganic nutrients. DOM photochemistry affects nitrogen cycling by converting bio-refractory dissolved organic nitrogen to labile inorganic nitrogen, mainly ammonium (NH4+). During the August 2009 Mackenzie Light and Carbon (MALINA) Program, the absorbed photon-based efficiency spectra of NH4+ photoproduction (i.e. photoammonification) were determined using water samples from the SE Beaufort Sea, including the Mackenzie River estuary, shelf, and Canada Basin. The photoammonification efficiency decreased with increasing wavelength across the ultraviolet and visible regimes and was higher in offshore waters than in shelf and estuarine waters. The efficiency was positively correlated with the molar nitrogen:carbon ratio of DOM and negatively correlated with the absorption coefficient of chromophoric DOM (CDOM). Combined with collateral measurements of CO2 and CO photoproduction, this study revealed a stoichiometry of DOM photochemistry with a CO2 : CO : NH4+ molar ratio of 165 : 11 : 1 in the estuary, 60 : 3 : 1 on the shelf, and 18 : 2 : 1 in the Canada Basin. The NH4+ efficiency spectra, along with solar photon fluxes, CDOM absorption coefficients and sea ice concentrations, were used to model the monthly surface and depth-integrated photoammonification rates in 2009. The summertime (June–August) rates at the surface reached 6.6 nmol l−1 d−1 on the Mackenzie Shelf and 3.7 nmol l−1 d−1 further offshore; the depth-integrated rates were correspondingly 8.8 μmol m−2 d−1 and 11.3 μmol m−2 d−1. The offshore depth-integrated rate in August (8.0 μmol m−2 d−1) was comparable to the missing dissolved inorganic nitrogen (DIN) source required to support the observed primary production in the upper 10-m layer of that area. The yearly NH4+ photoproduction in the entire study area was estimated to be 1.4 × 108 moles, with 85% of it being generated in summer when riverine DIN input is low. Photoammonification could mineralize 4% of the annual dissolved organic nitrogen (DON) exported from the Mackenzie River and provide a DIN source corresponding to 7% of the riverine DIN discharge and 1400 times the riverine NH4+ flux. Under a climate warming-induced ice-free scenario, these quantities could increase correspondingly to 6%, 11%, and 2100 times. Photoammonification is thus a significant nitrogen cycling term and may fuel previously unrecognized autotrophic and heterotrophic production pathways in the surface SE Beaufort Sea. |
format |
Article in Journal/Newspaper |
author |
Xie, H. Bélanger, S. Song, G. Benner, R. Taalba, A. Blais, M. Tremblay, J.-É. Babin, M. |
author_facet |
Xie, H. Bélanger, S. Song, G. Benner, R. Taalba, A. Blais, M. Tremblay, J.-É. Babin, M. |
author_sort |
Xie, H. |
title |
Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications |
title_short |
Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications |
title_full |
Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications |
title_fullStr |
Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications |
title_full_unstemmed |
Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications |
title_sort |
photoproduction of ammonium in the southeastern beaufort sea and its biogeochemical implications |
publisher |
Copernicus Publications |
publishDate |
2012 |
url |
https://doi.org/10.5194/bg-9-3047-2012 https://noa.gwlb.de/receive/cop_mods_00024695 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00024650/bg-9-3047-2012.pdf https://bg.copernicus.org/articles/9/3047/2012/bg-9-3047-2012.pdf |
geographic |
Canada Mackenzie River |
geographic_facet |
Canada Mackenzie River |
genre |
Beaufort Sea canada basin Mackenzie river Mackenzie Shelf Sea ice |
genre_facet |
Beaufort Sea canada basin Mackenzie river Mackenzie Shelf Sea ice |
op_relation |
Biogeosciences -- http://www.bibliothek.uni-regensburg.de/ezeit/?2158181 -- http://www.copernicus.org/EGU/bg/bg.html -- 1726-4189 https://doi.org/10.5194/bg-9-3047-2012 https://noa.gwlb.de/receive/cop_mods_00024695 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00024650/bg-9-3047-2012.pdf https://bg.copernicus.org/articles/9/3047/2012/bg-9-3047-2012.pdf |
op_rights |
uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/bg-9-3047-2012 |
container_title |
Biogeosciences |
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9 |
container_issue |
8 |
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3047 |
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3061 |
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1766372508504686592 |