Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean
The Southern Indian Ocean hosts diverse oceanic environments, pelagic communities, and predator populations that have recently led to the establishment of conservation areas and UNESCO World Heritage recognition. However, predator populations in this region have displayed signs of decline, likely at...
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Other Authors: | , , , , , , , , , |
Format: | Doctoral or Postdoctoral Thesis |
Language: | French |
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HAL CCSD
2023
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Online Access: | https://theses.hal.science/tel-04524647 https://theses.hal.science/tel-04524647/document https://theses.hal.science/tel-04524647/file/142844_IZARD_2023_archivage.pdf |
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ftuniversailles:oai:HAL:tel-04524647v1 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
Université de Versailles Saint-Quentin-en-Yvelines: HAL-UVSQ |
op_collection_id |
ftuniversailles |
language |
French |
topic |
Southern Indian Ocean Mesopelagic ecosystems Active acoustics Functional data analysis Analyse de données fonctionnelle Océan Indien Sud Écosystèmes mésopélagiques Acoustique active [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
spellingShingle |
Southern Indian Ocean Mesopelagic ecosystems Active acoustics Functional data analysis Analyse de données fonctionnelle Océan Indien Sud Écosystèmes mésopélagiques Acoustique active [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography Izard, Lloyd Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean |
topic_facet |
Southern Indian Ocean Mesopelagic ecosystems Active acoustics Functional data analysis Analyse de données fonctionnelle Océan Indien Sud Écosystèmes mésopélagiques Acoustique active [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography |
description |
The Southern Indian Ocean hosts diverse oceanic environments, pelagic communities, and predator populations that have recently led to the establishment of conservation areas and UNESCO World Heritage recognition. However, predator populations in this region have displayed signs of decline, likely attributed to the impacts of climate change and prey dynamics. These prey populations consist predominantly of zooplankton and micronekton, playing a crucial role in marine ecosystems by influencing biogeochemical cycles and the transfer of energy and biomass along the trophic web. Nevertheless, the study of their structuring is intricate due to their deep distribution in the mesopelagic zone (200-1000 m) and their daily vertical migrations, making it one of the least explored areas on a global scale. In this thesis, we employ active acoustics, which provides high spatial and vertical resolution for tracking these organisms, to investigate the structuring of mesopelagic ecosystems in two contrasting oceanic systems. We initially examined their responses in a transition zone between these oceans, within the Saint-Paul and Amsterdam Islands region. Our findings indicate that nycthemeral migrations are the primary factor vertically structuring pelagic organisms, even within a pronounced transition zone. Three spatially coherent regions were identified, sharing common environmental and acoustic features. Observations at 38 kHz (commonly used in hydroacoustics) confirmed increased biological activity in the subtropical zone and a minimum in the subantarctic zone. However, our analyses also reveal a distinct acoustic response based on the acoustic frequency considered, in terms of vertical structuring and integrated biomass. Additionally, the low levels measured in the Southern Ocean appear inconsistent with the high biomasses consumed by the large marine predator populations in this region. These observations highlight an acoustic resonance issue in the study of these organisms. To investigate this phenomenon, our second ... |
author2 |
Processus et interactions de fine échelle océanique (PROTEO) Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN) Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité) Sorbonne Université Jean-Benoît Charrassin Cédric Cotté |
format |
Doctoral or Postdoctoral Thesis |
author |
Izard, Lloyd |
author_facet |
Izard, Lloyd |
author_sort |
Izard, Lloyd |
title |
Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean |
title_short |
Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean |
title_full |
Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean |
title_fullStr |
Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean |
title_full_unstemmed |
Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean |
title_sort |
spatial structuring and variability of mesopelagic ecosystems in the southern indian ocean |
publisher |
HAL CCSD |
publishDate |
2023 |
url |
https://theses.hal.science/tel-04524647 https://theses.hal.science/tel-04524647/document https://theses.hal.science/tel-04524647/file/142844_IZARD_2023_archivage.pdf |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
https://theses.hal.science/tel-04524647 Océanographie. Sorbonne Université, 2023. Français. ⟨NNT : 2023SORUS621⟩ |
op_relation |
NNT: 2023SORUS621 tel-04524647 https://theses.hal.science/tel-04524647 https://theses.hal.science/tel-04524647/document https://theses.hal.science/tel-04524647/file/142844_IZARD_2023_archivage.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1799467404424642560 |
spelling |
ftuniversailles:oai:HAL:tel-04524647v1 2024-05-19T07:49:00+00:00 Spatial structuring and variability of mesopelagic ecosystems in the southern Indian ocean Structuration spatiale et variabilité des écosystèmes mésopélagiques dans l'Océan Indien Sud Izard, Lloyd Processus et interactions de fine échelle océanique (PROTEO) Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN) Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité) Sorbonne Université Jean-Benoît Charrassin Cédric Cotté 2023-12-19 https://theses.hal.science/tel-04524647 https://theses.hal.science/tel-04524647/document https://theses.hal.science/tel-04524647/file/142844_IZARD_2023_archivage.pdf fr fre HAL CCSD NNT: 2023SORUS621 tel-04524647 https://theses.hal.science/tel-04524647 https://theses.hal.science/tel-04524647/document https://theses.hal.science/tel-04524647/file/142844_IZARD_2023_archivage.pdf info:eu-repo/semantics/OpenAccess https://theses.hal.science/tel-04524647 Océanographie. Sorbonne Université, 2023. Français. ⟨NNT : 2023SORUS621⟩ Southern Indian Ocean Mesopelagic ecosystems Active acoustics Functional data analysis Analyse de données fonctionnelle Océan Indien Sud Écosystèmes mésopélagiques Acoustique active [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography info:eu-repo/semantics/doctoralThesis Theses 2023 ftuniversailles 2024-04-25T00:16:01Z The Southern Indian Ocean hosts diverse oceanic environments, pelagic communities, and predator populations that have recently led to the establishment of conservation areas and UNESCO World Heritage recognition. However, predator populations in this region have displayed signs of decline, likely attributed to the impacts of climate change and prey dynamics. These prey populations consist predominantly of zooplankton and micronekton, playing a crucial role in marine ecosystems by influencing biogeochemical cycles and the transfer of energy and biomass along the trophic web. Nevertheless, the study of their structuring is intricate due to their deep distribution in the mesopelagic zone (200-1000 m) and their daily vertical migrations, making it one of the least explored areas on a global scale. In this thesis, we employ active acoustics, which provides high spatial and vertical resolution for tracking these organisms, to investigate the structuring of mesopelagic ecosystems in two contrasting oceanic systems. We initially examined their responses in a transition zone between these oceans, within the Saint-Paul and Amsterdam Islands region. Our findings indicate that nycthemeral migrations are the primary factor vertically structuring pelagic organisms, even within a pronounced transition zone. Three spatially coherent regions were identified, sharing common environmental and acoustic features. Observations at 38 kHz (commonly used in hydroacoustics) confirmed increased biological activity in the subtropical zone and a minimum in the subantarctic zone. However, our analyses also reveal a distinct acoustic response based on the acoustic frequency considered, in terms of vertical structuring and integrated biomass. Additionally, the low levels measured in the Southern Ocean appear inconsistent with the high biomasses consumed by the large marine predator populations in this region. These observations highlight an acoustic resonance issue in the study of these organisms. To investigate this phenomenon, our second ... Doctoral or Postdoctoral Thesis Southern Ocean Université de Versailles Saint-Quentin-en-Yvelines: HAL-UVSQ |