Role of environmental variability on the response of Mediterranean corals to global change

• Main Author: Carbonne, Chloé
• Other Authors: Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, Jean-Pierre Gattuso, Núria Teixido, Steeve Comeau
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2022
• Subjects: Global change; Ocean acidification; Ocean warming; Coral; Mediterranean Sea; CO2 vents; Changement global; Acidification des océans; Réchauffement des océans; Coraux; Mer Méditerranée; Évents de CO2; [SDE.BE]Environmental Sciences/Biodiversity and Ecology
• Online Access: https://theses.hal.science/tel-04125434; https://theses.hal.science/tel-04125434v2/document; https://theses.hal.science/tel-04125434v2/file/CARBONNE_Chloe_these_2022.pdf

The increase of atmospheric CO2 is driving changes in the ocean’s physical and chemical properties. The projections by the IPCC under the high CO2 emission scenario RCP 8.5 suggest global sea surface temperature warming of 3.2°C and a decrease in pH of 0.3 units by the end of the century. Such changes have important consequences for ecosystems and the services they provide to humans. The Mediterranean Sea is a hot-spot of global change with warming sea surface temperature projected to be 20% higher than global projections and an increase in extreme events such as marine heatwaves. The main goal of this thesis is to determine the effects of present and future coastal environmental conditions on Mediterranean corals. Natural populations of corals from two volcanic CO2 vents in Ischia (Italy) are used. Local acidification of seawater occurs around the vents with pH values close to those expected by the end of the century. This research is focused on two Mediterranean long-lived corals that have key relevance for conservation as habitat-forming species: the zooxanthellate Cladocora caespitosa and the azooxanthellate Astroides calycularis. The main research questions are: (1) how present-day and future warming and/or acidification affect the physiology of Cladocora caespitosa and Astroides calycularis at every life stage (adult, gametogenesis, larvae, and recruits) and (2) does previous exposure to low pH at CO2 vents enhance their tolerance to future ocean acidification. To answer these questions, we combined environmental data, ecological field surveys at CO2 vent sites and reference sites with ambient pH, and laboratory experiments with controlled temperature and pH. This thesis provides new insights into the responses of adult colonies to warming on. I assess the physiological impact and potential recovery to different warming scenarios and heatwaves events, based on nine years of temperature data collected at the study site. I then study whether past exposure to low pH conditions confers tolerance to ocean ...