Grazers increase the sensitivity of coralline algae to ocean acidification and warming

• Published in: Journal of Sea Research
• Main Authors: Legrand, Erwann, Riera, Pascal, Lutier, Mathieu, Coudret, Jérôme, Grall, Jacques, Martin, Sophie
• Other Authors: Adaptation et diversité en milieu marin (ADMM), Institut national des sciences de l'Univers (INSU - CNRS)-Station biologique de Roscoff = Roscoff Marine Station (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Station biologique de Roscoff = Roscoff Marine Station (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), 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), ANR-10-BTBR-0004,IDEALG,Biotechnologies pour la valorisation des macroalgues(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Global change; Algal-herbivore interactions; CO2; Temperature; Calcareous algae; Grazing; [SDE]Environmental Sciences; [SDE.MCG]Environmental Sciences/Global Changes; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Ocean acidification
• Online Access: https://hal.science/hal-02360270; https://doi.org/10.1016/j.seares.2019.03.001

International audience Coralline algae are expected to be adversely impacted by ocean acidification and warming. Most research on these algae has involved experiments on isolated species, without considering species interactions, such as grazing. This myopic view is challenging because the impact of climate change on coralline algae will depend on the direct impacts on individual coralline species and the indirect effects of altered interactions with other species. Here, we tested the influence of grazing on the response of the coralline alga Lithothamnion corallioides to near-future ocean acidification and warming. Two three-month experiments were performed in the winter and summer seasons in mesocosms under crossed conditions of pCO(2) (ambient and high pCO(2)) and temperature (ambient and +3 degrees C) in the presence and absence of grazers. In the winter, L. corallioides photosynthesis decreased with rising temperature in the presence of grazers, while calcification increased. It is likely that increased calcification may act as a structural protection to prevent damage from grazing. However, increasing calcification rates in the presence of grazers may be detrimental to other physiological processes, such as photosynthesis. In the summer, L. corallioides primary production, respiration, and calcification were higher in the presence of grazers than in their absence. Light calcification rates were reduced under high pCO(2) in the presence of grazers only. Moreover, dark calcification rates were more adversely affected by pCO(2) increase in the presence of grazers. Through their feeding activity, grazers may alter the structural integrity of thalli and increase the sensitivity of coralline algae to ocean acidification. Our results indicate that both season and grazing play a key role in the response of L. corallioides to acidification and warming. Seasonal variations and species interactions are thus critical to consider to make ecologically relevant predictions of the effects of future environmental changes.