{"id":23963,"date":"2025-12-06T15:40:10","date_gmt":"2025-12-06T14:40:10","guid":{"rendered":"https:\/\/www.mio.osupytheas.fr\/?p=23963"},"modified":"2025-12-10T16:06:44","modified_gmt":"2025-12-10T15:06:44","slug":"helene-thibault-these","status":"publish","type":"post","link":"https:\/\/www.mio.osupytheas.fr\/fr\/helene-thibault-these\/","title":{"rendered":"F\u00e9licitations \u00e0 H\u00e9l\u00e8ne Thibault qui a soutenu sa th\u00e8se le mercredi 10 d\u00e9cembre 2025"},"content":{"rendered":"\t\t
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H\u00e9l\u00e8ne Thibault<\/strong> a soutenu sa th\u00e8se le mercredi 10 d\u00e9cembre 2025<\/strong> \u00e0 l\u2019Amphith\u00e9\u00e2tre OCEANOMED sur le sujet suivant : R\u00f4le du micronecton dans les flux de carbone de l’Atlantique Nord-Est : approche par mod\u00e9lisation et donn\u00e9es in situ.<\/em><\/p>

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Membres du Jury<\/strong><\/h4>
  • Jean-Christophe POGGIALE, Professeur AMU – Pr\u00e9sident du jury<\/li>
  • Laurent BOPP, Directeur de recherche CNRS – Rapporteur<\/li>
  • Anne LORRAIN, Directrice de recherche IRD – Rapportrice<\/li>
  • Christophe MENKES, Directeur de recherche IRD – Examinateur (en visioconf\u00e9rence depuis la Nouvelle Cal\u00e9donie)<\/li>
  • Tiphaine CHOUVELON, Ing\u00e9nieure de recherche ULR – Examinatrice<\/li>
  • Fr\u00e9d\u00e9ric M\u00e9nard, Directeur de recherche IRD – Co-Directeur de th\u00e8se<\/li>
  • S\u00e9verine MARTINI, Charg\u00e9e de recherche CNRS – Co-Directrice de th\u00e8se<\/li><\/ul>

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    R\u00e9sum\u00e9<\/strong><\/h4>

    The mesopelagic zone (200\u20131,000 m), also referred to as the \u201ctwilight zone\u201d, plays a central role in the ocean\u2019s biological carbon pump (BCP), regulating global climate by transferring organic carbon from surface waters to the deep ocean. Among its inhabitants, micronekton\u2014small fishes, crustaceans, cephalopods, and gelatinous organisms (2\u201320 cm)\u2014are key intermediaries linking zooplankton to top predators and driving active carbon transport through diel vertical migrations (DVM). Despite their ecological importance, major uncertainties remain regarding their biomass, community composition, vertical distribution, and contribution to carbon sequestration due to observational and modeling limitations. This thesis aims to improve understanding of the role of micronekton in midwater ecosystems and their contribution to the BCP by combining field observations, and mechanistic modeling. Using data collected during the APERO campaign in the Northeast Atlantic (PAP-SO), the thesis examines the vertical structure, trophic organization, and functional diversity of micronekton communities through isotopic and functional analyses. Results reveal strong vertical segregation, with migrating functional groups dominating both in abundance and biomass, emphasizing their role in transferring surface-derived carbon to depth and sustaining mesopelagic predators. A mechanistic model was developed to explicitly represent micronekton metabolism and vertical migration. The model quantifies carbon export induced by micronekton DVM under varying environmental conditions of light, temperature, and primary production. Sensitivity analyses identify respiration and capture rates as key parameters controlling active flux, with seasonal, taxonomic, and community size variability modulating export efficiency. Calibrated with acoustic and trawl data, model estimates obtained under post-bloom conditions revealed clear contrasts across mesoscale features: cyclonic eddies of subpolar origin, dominated by the glacier lanternfish Benthosema glaciale, exhibited the highest micronekton biomass and carbon export, highlighting the strong coupling between community structure and biogeochemical fluxes. Altogether, this work contributes to the understanding of micronekton-mediated carbon flow and export by integrating assessment of micronekton ecology and biogeochemical function in a temperate system. The results underline the need for global observation networks and data\u2013model integration to assess the resilience and future role of the twilight zone in ocean carbon cycling in a context of global change.<\/p>

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    Keywords<\/strong><\/h4>

    Micronekton, mesopelagic zone, biological carbon pump, ecology, trophic interactions<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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    H\u00e9l\u00e8ne Thibault a soutenu sa th\u00e8se le mercredi 10 d\u00e9cembre 2025 \u00e0 l\u2019Amphith\u00e9\u00e2tre OCEANOMED sur le sujet suivant : R\u00f4le du micronecton dans les flux de carbone de l’Atlantique Nord-Est […]<\/p>\n","protected":false},"author":319,"featured_media":24327,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[17,1,26],"tags":[],"class_list":["post-23963","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-a-la-une","category-actualites","category-theses"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/posts\/23963","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/users\/319"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/comments?post=23963"}],"version-history":[{"count":26,"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/posts\/23963\/revisions"}],"predecessor-version":[{"id":24334,"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/posts\/23963\/revisions\/24334"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/media\/24327"}],"wp:attachment":[{"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/media?parent=23963"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/categories?post=23963"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/fr\/wp-json\/wp\/v2\/tags?post=23963"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}