First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic)
International audience Although not systematically considered as oxygen minimum zones, River-dominated Ocean Margins are sensitive to oxygen depletions. For example, the continental shelf off the Gironde, which flows into the Bay of Biscay, had not yet been studied from this perspective although rec...
Published in: | Frontiers in Marine Science |
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Format: | Article in Journal/Newspaper |
Language: | English |
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2022
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Online Access: | https://hal.science/hal-03824842 https://hal.science/hal-03824842/document https://hal.science/hal-03824842/file/fmars-09-1006453.pdf https://doi.org/10.3389/fmars.2022.1006453 |
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ftunivnantes:oai:HAL:hal-03824842v1 2023-05-15T17:38:36+02:00 First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic) Dubosq, Nicolas Schmidt, Sabine Sudre, Joël Rigaud, Sylvain Lamarque, Bastien Danilo, Martin Grémare, Antoine Deflandre, Bruno UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC) Observatoire aquitain des sciences de l'univers (OASU) Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE) Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS) 2022-10-07 https://hal.science/hal-03824842 https://hal.science/hal-03824842/document https://hal.science/hal-03824842/file/fmars-09-1006453.pdf https://doi.org/10.3389/fmars.2022.1006453 en eng HAL CCSD Frontiers Media info:eu-repo/semantics/altIdentifier/doi/10.3389/fmars.2022.1006453 hal-03824842 https://hal.science/hal-03824842 https://hal.science/hal-03824842/document https://hal.science/hal-03824842/file/fmars-09-1006453.pdf doi:10.3389/fmars.2022.1006453 http://creativecommons.org/licenses/by/ info:eu-repo/semantics/OpenAccess ISSN: 2296-7745 Frontiers in Marine Science https://hal.science/hal-03824842 Frontiers in Marine Science, 2022, 9, ⟨10.3389/fmars.2022.1006453⟩ deoxygenation continental shelf seasonal evolution stratification Bay of Biscay dissolved oxygen [SDE.MCG]Environmental Sciences/Global Changes info:eu-repo/semantics/article Journal articles 2022 ftunivnantes https://doi.org/10.3389/fmars.2022.1006453 2023-02-08T02:16:21Z International audience Although not systematically considered as oxygen minimum zones, River-dominated Ocean Margins are sensitive to oxygen depletions. For example, the continental shelf off the Gironde, which flows into the Bay of Biscay, had not yet been studied from this perspective although recent simulations suggested that this area should already have experienced deoxygenations in recent decades. To fill this gap, profiles of temperature, salinity and dissolved oxygen were performed in the water column of the continental shelf off the Gironde during seven cruises distributed over the different seasons between 2016 and 2021. Turbidity, chlorophyll- a and pH were also measured during some of these cruises. In winter, the water column was slightly stratified due to high river flows. Then, a seasonal thermal stratification was present from spring to autumn. Similarly, dissolved oxygen showed a seasonal dynamic with: a well-oxygenated water column in winter, an oxygen oversaturation in the first 20 meters during the spring bloom, and then a progressive oxygen depletion in bottom waters until reaching an oxygen saturation minimum down to 45% in autumn. These deoxygenations are explained by the seasonal stratification that isolates the bottom waters from spring to autumn, and are likely enhanced by the advection of deoxygenated waters from the north of the Bay of Biscay and the settling of the organic matter produced in surface waters. A better understanding of these processes in the context of global warming undoubtedly requires better documentation of dissolved oxygen variability through the implementation of a long-term and continuous in situ monitoring. Article in Journal/Newspaper North East Atlantic Université de Nantes: HAL-UNIV-NANTES Frontiers in Marine Science 9 |
institution |
Open Polar |
collection |
Université de Nantes: HAL-UNIV-NANTES |
op_collection_id |
ftunivnantes |
language |
English |
topic |
deoxygenation continental shelf seasonal evolution stratification Bay of Biscay dissolved oxygen [SDE.MCG]Environmental Sciences/Global Changes |
spellingShingle |
deoxygenation continental shelf seasonal evolution stratification Bay of Biscay dissolved oxygen [SDE.MCG]Environmental Sciences/Global Changes Dubosq, Nicolas Schmidt, Sabine Sudre, Joël Rigaud, Sylvain Lamarque, Bastien Danilo, Martin Grémare, Antoine Deflandre, Bruno First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic) |
topic_facet |
deoxygenation continental shelf seasonal evolution stratification Bay of Biscay dissolved oxygen [SDE.MCG]Environmental Sciences/Global Changes |
description |
International audience Although not systematically considered as oxygen minimum zones, River-dominated Ocean Margins are sensitive to oxygen depletions. For example, the continental shelf off the Gironde, which flows into the Bay of Biscay, had not yet been studied from this perspective although recent simulations suggested that this area should already have experienced deoxygenations in recent decades. To fill this gap, profiles of temperature, salinity and dissolved oxygen were performed in the water column of the continental shelf off the Gironde during seven cruises distributed over the different seasons between 2016 and 2021. Turbidity, chlorophyll- a and pH were also measured during some of these cruises. In winter, the water column was slightly stratified due to high river flows. Then, a seasonal thermal stratification was present from spring to autumn. Similarly, dissolved oxygen showed a seasonal dynamic with: a well-oxygenated water column in winter, an oxygen oversaturation in the first 20 meters during the spring bloom, and then a progressive oxygen depletion in bottom waters until reaching an oxygen saturation minimum down to 45% in autumn. These deoxygenations are explained by the seasonal stratification that isolates the bottom waters from spring to autumn, and are likely enhanced by the advection of deoxygenated waters from the north of the Bay of Biscay and the settling of the organic matter produced in surface waters. A better understanding of these processes in the context of global warming undoubtedly requires better documentation of dissolved oxygen variability through the implementation of a long-term and continuous in situ monitoring. |
author2 |
UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC) Observatoire aquitain des sciences de l'univers (OASU) Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE) Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Dubosq, Nicolas Schmidt, Sabine Sudre, Joël Rigaud, Sylvain Lamarque, Bastien Danilo, Martin Grémare, Antoine Deflandre, Bruno |
author_facet |
Dubosq, Nicolas Schmidt, Sabine Sudre, Joël Rigaud, Sylvain Lamarque, Bastien Danilo, Martin Grémare, Antoine Deflandre, Bruno |
author_sort |
Dubosq, Nicolas |
title |
First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic) |
title_short |
First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic) |
title_full |
First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic) |
title_fullStr |
First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic) |
title_full_unstemmed |
First observations of seasonal bottom water deoxygenation off the Gironde estuary (Bay of Biscay, North East Atlantic) |
title_sort |
first observations of seasonal bottom water deoxygenation off the gironde estuary (bay of biscay, north east atlantic) |
publisher |
HAL CCSD |
publishDate |
2022 |
url |
https://hal.science/hal-03824842 https://hal.science/hal-03824842/document https://hal.science/hal-03824842/file/fmars-09-1006453.pdf https://doi.org/10.3389/fmars.2022.1006453 |
genre |
North East Atlantic |
genre_facet |
North East Atlantic |
op_source |
ISSN: 2296-7745 Frontiers in Marine Science https://hal.science/hal-03824842 Frontiers in Marine Science, 2022, 9, ⟨10.3389/fmars.2022.1006453⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.3389/fmars.2022.1006453 hal-03824842 https://hal.science/hal-03824842 https://hal.science/hal-03824842/document https://hal.science/hal-03824842/file/fmars-09-1006453.pdf doi:10.3389/fmars.2022.1006453 |
op_rights |
http://creativecommons.org/licenses/by/ info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.3389/fmars.2022.1006453 |
container_title |
Frontiers in Marine Science |
container_volume |
9 |
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1766139109481381888 |