Phenotypic plasticity of oysters to ocean acidification in temperate and tropical environments

• Main Author: Lutier, Mathieu
• 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, Fabrice Pernet
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2022
• Subjects: Ocean acidification; Oyster; Phenotypic plasticity; Reaction norms; Tipping point; Acidification des océans; Huître; Normes de réaction; Plasticité phénotypique; Point de bascule; [SDV.BA]Life Sciences [q-bio]/Animal biology; Pacific; Pacific oyster
• Online Access: https://theses.hal.science/tel-04213535; https://theses.hal.science/tel-04213535/document; https://theses.hal.science/tel-04213535/file/These-2022-SML-Biologie_marine-LUTIER_Mathieu.pdf

Phenotypic plasticity is the first defense of organisms against global changes, buffering their impact on individual fitness. However, this buffering capacity is limited by the tipping point beyond which species will have to adapt or disappear. These tipping points are determined by modeling the reaction norms for phenotypic traits over a wide range of environmental conditions. This approach is used anecdotally to study the impacts of ocean acidification (OA) on marine organisms. Therefore, tipping points remain unknown for the Pacific oyster and the pearl oyster whose population decline would have a great economic an environmental impact. This thesis work establishes the first holistic reactions norms, at macrophysiological (physiological rates, shell parameters) and molecular scales (transcriptomic, lipidomic), in organisms exposed to a wide range of pH in temperate and tropical environments.Thus, we identified a tolerance threshold at pH 7.3-6.9 below which the fitness of Pacific oyster and that of pearl oyster are impacted. Short-term exposure to pH below the tipping points will have a long-term impact on the Pacific oyster which will not be able to compensate for growth stunting. The tolerance threshold to OA is already reached in habitats of the Pacific oyster during extreme acidification events which must increase in the future, threatening natural and farmed populations. The ambient pH conditions encountered by pearl oysters remain unknown, requiring the establishment of large-scale pH monitoring in order to conclude on the future of the species. La plasticité phénotypique est la première ligne de défense des espèces face aux changements globaux, tamponnant leur impact sur la fitness individuelle. Toutefois, cet effet tampon est limité par un point de bascule au-delà duquel les espèces devront s’adapter ou disparaître. Ces points de bascule sont déterminés en modélisant les normes de réaction des traits phénotypiques sur une large gamme de variations environnementales. Cette approche reste anecdotique ...