Cascading Effects of Ocean Acidification in a Rocky Subtidal Community

• Published in: PLoS ONE
• Main Authors: Asnaghi, Valentina, Chiantore, Mariachiara, Mangialajo, Luisa, Gazeau, Frédéric, Francour, Patrice, Alliouane, Samir, Gattuso, Jean-Pierre
• Other Authors: Department of Earth, Environmental and Life Sciences (DISTAV), Università degli studi di Genova = University of Genoa (UniGe), Ecosystèmes Côtiers Marins et Réponses aux Stress (ECOMERS), Université Nice Sophia Antipolis (1965 - 2019) (UNS)-Centre National de la Recherche Scientifique (CNRS)-Université Côte d'Azur (UniCA), Laboratoire d'océanographie de Villefranche (LOV), Observatoire océanologique de Villefranche-sur-mer (OOVM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [SDV.EE.BIO]Life Sciences [q-bio]/Ecology; environment/Bioclimatology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Ocean acidification
• Online Access: https://hal.sorbonne-universite.fr/hal-01535594; https://hal.sorbonne-universite.fr/hal-01535594/document; https://hal.sorbonne-universite.fr/hal-01535594/file/journal.pone.0061978.PDF; https://doi.org/10.1371/journal.pone.0061978

International audience Temperate marine rocky habitats may be alternatively characterized by well vegetated macroalgal assemblages or barren grounds, as a consequence of direct and indirect human impacts (e.g. overfishing) and grazing pressure by herbivorous organisms. In future scenarios of ocean acidification, calcifying organisms are expected to be less competitive: among these two key elements of the rocky subtidal food web, coralline algae and sea urchins. In order to highlight how the effects of increased pCO 2 on individual calcifying species will be exacerbated by interactions with other trophic levels, we performed an experiment simultaneously testing ocean acidification effects on primary producers (calcifying and non-calcifying algae) and their grazers (sea urchins). Artificial communities, composed by juveniles of the sea urchin Paracentrotus lividus and calcifying (Corallina elongata) and non-calcifying (Cystoseira amentacea var stricta, Dictyota dichotoma) macroalgae, were subjected to pCO 2 levels of 390, 550, 750 and 1000 matm in the laboratory. Our study highlighted a direct pCO 2 effect on coralline algae and on sea urchin defense from predation (test robustness). There was no direct effect on the non-calcifying macroalgae. More interestingly, we highlighted diet-mediated effects on test robustness and on the Aristotle's lantern size. In a future scenario of ocean acidification a decrease of sea urchins' density is expected, due to lower defense from predation, as a direct consequence of pH decrease, and to a reduced availability of calcifying macroalgae, important component of urchins' diet. The effects of ocean acidification may therefore be contrasting on well vegetated macroalgal assemblages and barren grounds: in the absence of other human impacts, a decrease of biodiversity can be predicted in vegetated macroalgal assemblages, whereas a lower density of sea urchin could help the recovery of shallow subtidal rocky areas affected by overfishing from barren grounds to assemblages dominated ...