Coastal ecosystems connect land and sea through exchanges of material and energy, generating numerous ecosystem services. However, the biosphere at this interface is increasingly vulnerable to all the disturbances linked with climate change, including increased atmospheric CO₂, changes in productivity base or altered carbon and nutrient fluxes from land to sea. As a result of fossil fuels burning, ¹³C/¹²C values of atmospheric CO₂ are decreasing (i.e. the Suess effect). This decrease eventually reflects in the ¹³C/¹²C values of marine organism tissues, which can confound interpretation of e.g. organic carbon cycling, dietary carbon origin or food web dynamics. In a multi-ecosystem study, we measured spanning 1 to 4 decades the ¹³C/¹²C of bivalve tissues, often used as sentinel organisms for environmental change. Our 33 sites are distributed along the French littoral and encompassing a distance gradient from estuaries. We aimed to identify the Suess effect on bivalves and disentangle its signal from other environmental disturbances, especially terrestrial inputs from rivers. Across all sites, we observed a decrease of 0.1 to 1.0 ‰ per decade in ¹³C/¹²C bivalve tissues, with a generally less pronounced decrease for the sites close to estuarine mouths. We ultimately correlated ¹³C/¹²C values with environmental data, especially river inputs, which relate to the use and management of watersheds, in order to explain the ¹³C/¹²C patterns. Our results contribute to the understanding of the complex and interacting effects of human disturbances on coastal ecosystem functioning.

Primary Presenter: Camilla Liénart, University of Bordeaux (camilla.lienart@u-bordeaux.fr)

Authors:

Camilla Liénart, Université de Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France  ()

Alan Fournioux, Université de Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France  ()

Arnaud Lheureux, Unité Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Muséum National d’Histoire Naturelle, CNRS, IRD, Sorbonne Université, Université de Caen Normandie, Université des Antilles, Paris, France  ()

Andrius Garbaras, Center for Physical Sciences and Technology, Vilnius, Lithuania  ()

Valérie David, Université de Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France  ()

Xavier de Montaudouin, Université de Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France  ()

Hugues Blanchet, Université de Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France  ()

Nicolas Briant, IFREMER Centre Atlantique, CCEM, Nantes, France  ()

Pauline Le Monier, IFREMER Centre Atlantique, CCEM, Nantes, France  ()

Anne Grouhel-Pellouin, IFREMER Centre Atlantique, CCEM, Nantes, France  ()

Stanislas Dubois, IFREMER DYNECO/LEBCO, Brest, France  ()

Aline Gagnery, IFREMER DYNECO/LEBCO, Brest, France  ()

Mickael Vasquez, IFREMER DYNECO/LEBCO, Brest, France  ()

Nicolas Savoye, Université de Bordeaux, CNRS, Bordeaux INP, EPOC, UMR 5805, F-33600 Pessac, France  ()