High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice
We report concentration and nitrogen and oxygen isotopic measurements of nitrate, total dissolved nitrogen, and particulate nitrogen from Antarctic landfast sea ice, covering almost the complete seasonal cycle of sea ice growth and decay (from April to November). When sea ice forms in autumn, ice al...
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ftunivbruxelles:oai:dipot.ulb.ac.be:2013/205410 2023-05-15T13:44:43+02:00 High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice Fripiat, François Sigman, Daniel M Massé, Guillaume Tison, Jean-Louis 2015-04 1 full-text file(s): application/pdf http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/205410 https://dipot.ulb.ac.be/dspace/bitstream/2013/205410/3/205410.pdf en eng uri/info:doi/10.1002/2014JC010583 uri/info:scp/84929170240 https://dipot.ulb.ac.be/dspace/bitstream/2013/205410/3/205410.pdf http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/205410 1 full-text file(s): info:eu-repo/semantics/restrictedAccess Journal of geophysical research. Oceans, 120 (4 Sciences de l'espace Phénomènes atmosphériques Géographie physique Sciences de la terre et du cosmos Antarctic isotopes nitrogen nutrients sea ice info:eu-repo/semantics/article info:ulb-repo/semantics/articlePeerReview info:ulb-repo/semantics/openurl/article 2015 ftunivbruxelles 2022-06-12T21:10:22Z We report concentration and nitrogen and oxygen isotopic measurements of nitrate, total dissolved nitrogen, and particulate nitrogen from Antarctic landfast sea ice, covering almost the complete seasonal cycle of sea ice growth and decay (from April to November). When sea ice forms in autumn, ice algae growth depletes nitrate and accumulates organic N within the ice. Subsequent low biological activity in winter imposes minor variations in the partitioning of fixed N. In early spring, the coupling between nitrate assimilation and brine convection at the sea ice bottom traps a large amount of fixed N within sea ice, up to 20 times higher than in the underlying seawater. At this time, remineralization and nitrification also accelerate, yielding nitrate concentrations up to 5 times higher than in seawater. Nitrate δ 15 N and δ 18 O are both elevated, indicating a near-balance between nitrification and nitrate assimilation. These findings require high microbially mediated turnover rates for the large fixed N pools, including nitrate. When sea ice warms in the spring, ice algae grow through the full thickness of the ice. The warming stratifies the brine network, which limits the exchange with seawater, causing the once-elevated nitrate pool to be nearly completely depleted. The nitrate isotope data point to light limitation at the base of landfast ice as a central characteristic of the environment, affecting its N cycling (e.g. allowing for nitrification) and impacting algal physiology (e.g. as reflected in the N and O isotope effects of nitrate assimilation). Key Points: Spring accumulation of fixed nitrogen above seawater values High turnover rates of fixed N pool, including nitrate Light availability affects sea ice nitrate isotopes distribution SCOPUS: ar.j FLWIN SCOPUS: ar.j info:eu-repo/semantics/published Article in Journal/Newspaper Antarc* Antarctic ice algae Sea ice DI-fusion : dépôt institutionnel de l'Université libre de Bruxelles (ULB) Antarctic |
institution |
Open Polar |
collection |
DI-fusion : dépôt institutionnel de l'Université libre de Bruxelles (ULB) |
op_collection_id |
ftunivbruxelles |
language |
English |
topic |
Sciences de l'espace Phénomènes atmosphériques Géographie physique Sciences de la terre et du cosmos Antarctic isotopes nitrogen nutrients sea ice |
spellingShingle |
Sciences de l'espace Phénomènes atmosphériques Géographie physique Sciences de la terre et du cosmos Antarctic isotopes nitrogen nutrients sea ice Fripiat, François Sigman, Daniel M Massé, Guillaume Tison, Jean-Louis High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice |
topic_facet |
Sciences de l'espace Phénomènes atmosphériques Géographie physique Sciences de la terre et du cosmos Antarctic isotopes nitrogen nutrients sea ice |
description |
We report concentration and nitrogen and oxygen isotopic measurements of nitrate, total dissolved nitrogen, and particulate nitrogen from Antarctic landfast sea ice, covering almost the complete seasonal cycle of sea ice growth and decay (from April to November). When sea ice forms in autumn, ice algae growth depletes nitrate and accumulates organic N within the ice. Subsequent low biological activity in winter imposes minor variations in the partitioning of fixed N. In early spring, the coupling between nitrate assimilation and brine convection at the sea ice bottom traps a large amount of fixed N within sea ice, up to 20 times higher than in the underlying seawater. At this time, remineralization and nitrification also accelerate, yielding nitrate concentrations up to 5 times higher than in seawater. Nitrate δ 15 N and δ 18 O are both elevated, indicating a near-balance between nitrification and nitrate assimilation. These findings require high microbially mediated turnover rates for the large fixed N pools, including nitrate. When sea ice warms in the spring, ice algae grow through the full thickness of the ice. The warming stratifies the brine network, which limits the exchange with seawater, causing the once-elevated nitrate pool to be nearly completely depleted. The nitrate isotope data point to light limitation at the base of landfast ice as a central characteristic of the environment, affecting its N cycling (e.g. allowing for nitrification) and impacting algal physiology (e.g. as reflected in the N and O isotope effects of nitrate assimilation). Key Points: Spring accumulation of fixed nitrogen above seawater values High turnover rates of fixed N pool, including nitrate Light availability affects sea ice nitrate isotopes distribution SCOPUS: ar.j FLWIN SCOPUS: ar.j info:eu-repo/semantics/published |
format |
Article in Journal/Newspaper |
author |
Fripiat, François Sigman, Daniel M Massé, Guillaume Tison, Jean-Louis |
author_facet |
Fripiat, François Sigman, Daniel M Massé, Guillaume Tison, Jean-Louis |
author_sort |
Fripiat, François |
title |
High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice |
title_short |
High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice |
title_full |
High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice |
title_fullStr |
High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice |
title_full_unstemmed |
High turnover rates indicated by changes in the fixed N forms and their stable isotopes in Antarctic landfast sea ice |
title_sort |
high turnover rates indicated by changes in the fixed n forms and their stable isotopes in antarctic landfast sea ice |
publishDate |
2015 |
url |
http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/205410 https://dipot.ulb.ac.be/dspace/bitstream/2013/205410/3/205410.pdf |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic ice algae Sea ice |
genre_facet |
Antarc* Antarctic ice algae Sea ice |
op_source |
Journal of geophysical research. Oceans, 120 (4 |
op_relation |
uri/info:doi/10.1002/2014JC010583 uri/info:scp/84929170240 https://dipot.ulb.ac.be/dspace/bitstream/2013/205410/3/205410.pdf http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/205410 |
op_rights |
1 full-text file(s): info:eu-repo/semantics/restrictedAccess |
_version_ |
1766205112481480704 |