Functioning of Arctic and sub-Arctic shallow benthic ecosystems in highly-stratified coastal systems

• Main Author: Bridier, Guillaume
• Other Authors: Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne occidentale - Brest, Laurent Chauvaud
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2020
• Subjects: Benthic macrofauna; Stratification; Food webs; Shallow Coastal ecosystems; High-Arctic; Sub-Arctic; Macrofaune benthique; Réseaux trophiques; Ecosystèmes côtiers peu profonds; Haut-Arctique; Sub-Arctique; [SDV.EE.ECO]Life Sciences [q-bio]/Ecology; environment/Ecosystems; Arctic; Greenland; Arctic Archipelago; Arctique*; Climate change; Newfoundland
• Online Access: https://theses.hal.science/tel-03588863; https://theses.hal.science/tel-03588863/document; https://theses.hal.science/tel-03588863/file/These-2020-SML-Ecologie_marine-BRIDIER_Guillaume.pdf

Under climate change, Arctic and sub-Arctic Coastal Systems expérience one of the largest increases in stratification at the global scale due to warming and/or freshening of their surface waters. However, the subséquent impacts of these environmental changes on the functioning of Coastal benthic ecosystems is still poorly understood. This thesis aims to study how future increases in stratification in these ecosystems could affect the organic matter quality, pelagic-benthic coupling intensity and benthic food web structures. Two Coastal Systems subject to strong seasonal variations in sea surface température and salinity were studied: a high- arctic fjord (Young Sound, NE Greenland) characterized by strong haline stratification and a sub-Arctic archipelago (Saint-Pierre-et-Miquelon, Newfoundland continental shelf) exposed to strong thermal stratification. In the first part of this PhD we show that strong stratification reduces the quality of pelagic organic matter sources and intensity of organic matter transfers from surface waters toward the benthic compartiment. On the other hand, no impact was observed on the quality of benthic organic matter sources. In the second part we show that stratification does not alter benthic food web structures thanks to the high trophic plasticity of primary consumers and high levels of omnivory in the community. In addition, benthic primary production in Coastal environment could potentially provide an alternative source of organic matter to pelagic primary production for primary consumers during high stratification conditions. Through these results, we propose several conceptual models describing the potential évolutions of these ecosystems under climate change and we show the importance of considering the singularity of coastal ecosystems as well as their small-scale spatial variations. Face au changement climatique, les systèmes côtiers Arctiques et sub-Arctiques subissent l’une des plus fortes augmentions de stratification à l’échelle de la planète en raison d’un ...