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.
Legrand E., 2017. Impact of ocean acidification and warming on the diversity and the functioning of macroalgal communities. PhD thesis, Université Pierre et Marie Curie, Paris. 285 p. Thesis.
