Impact of ocean acidification and warming on the diversity and the functioning of macroalgal communities

• Main Author: Legrand, Erwann
• Other Authors: Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff Roscoff (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris VI, Sophie Martin, Pascal Riera
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2017
• Subjects: Climate change; Marine community; Température; Co2; Bancs de maërl; Cuvettes intertidales; Communauté; Interactions spécifiques; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Ocean acidification
• Online Access: https://theses.hal.science/tel-01813201; https://theses.hal.science/tel-01813201/document; https://theses.hal.science/tel-01813201/file/2017PA066505.pdf

Predicted ocean acidification and warming for the end of the century may have drastic consequences on the structure and functioning of marine ecosystems. However, a lack of knowledge persists on the impact of future changes on the response of marine communities. This thesis aims to provide new understanding of the impact of ocean acidification and warming at the community level. For this, two ecosystems have been considered: rockpools, characterized by high physico-chemical variations, and maerl beds, with smaller variations. In the laboratory, artificial assemblages were created from the main calcareous and fleshy macroalgal and grazer species present in these two ecosystems. Created assemblages have been subjected to ambient and future temperature and pCO2 conditions. Ocean acidification and warming altered the structure and functioning of maerl bed assemblages, through an increase in the productivity of non-calcareous macroalgae and a decline in maërl calcification rates. The physiology of grazers is negatively impacted by future changes, which altered assemblages’ trophic structure. On the other hand, ocean acidification and warming had no effect on the productivity of rockpool assemblages. The highly variable environment may thus increase the resistance of rockpool communities to future changes, compared to communities from more stable environments, such as maerl beds. L'acidification et le réchauffement des océans prévus pour la fin du siècle sont susceptibles d'avoir des conséquences drastiques sur la structure et le fonctionnement des écosystèmes marins. Un manque de connaissance persiste cependant quant à l'impact des changements futurs sur la réponse des communautés marines. Cette thèse a pour objectif de fournir de nouveaux éléments de compréhension de l'impact de l'acidification et du réchauffement des océans à l'échelle communautaire, en considérant un écosystème aux propriétés physico-chimiques hypervariables, les cuvettes intertidales, et un écosystème plus stable, les bancs de maërl. Des ...