Spatial variability of stable isotope ratios in oysters (Crassostrea gigas) and primary producers along an estuarine gradient (Bay of Brest, France)

• Published in: Estuaries and Coasts
• Main Authors: Marchais, Violette, Schaal, Gauthier, Grall, Jacques, Lorrain, Anne, Nerot, Caroline, Richard, Pierre, Chauvaud, Laurent
• Other Authors: Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-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)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), INSU EC2CO program ISOBENT; GIS- Europole Mer
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: biofilm; carbon; nitrogen; food web; estuary; Bay of Brest; [SDV.EE.IEO]Life Sciences [q-bio]/Ecology; environment/Symbiosis; Inner Bay; Crassostrea gigas
• Online Access: https://hal.archives-ouvertes.fr/hal-00832092; https://hal.archives-ouvertes.fr/hal-00832092v2/document; https://hal.archives-ouvertes.fr/hal-00832092v2/file/publication_version_HAL.pdf; https://doi.org/10.1007/s12237-012-9584-x

International audience This study aimed at characterizing the diet of the oyster Crassostrea gigas along an estuarine gradient in the Bay of Brest (France), through stable isotope (δ13C and δ15N) measurements in primary producers and wild oysters. The contribution of different potential food sources to the diet of C. gigas was estimated at high spatial resolution (over a gradient of 40 km with samplings every 2 km) to identify ecological transition zones, and highlighted the dominance of resuspended biofilm in oysters diet. Although the different primary producers did not display any obvious pattern along the estuarine gradient, the stable isotope signatures of C. gigas differed among estuarine, inner Bay and open sea sites. In particular, a striking 15N depletion pattern was found along the gradient which allowed to identify seven homogeneous groups. Moreover, some unexpected values found at two stations within the estuary revealed localized anthropogenic disturbances. Overall, our results suggest that suspension-feeders might be better indicators of ecosystem functioning than primary producers, and reflect the different ecological processes occurring along estuarine gradients, including localized anthropogenic inputs. We suggest that the usefulness of suspension-feeders as indicators of ecosystem functional typology lies in the dominance of benthic material in their diet, which results in locally occurring processes being reflected in oysters' stable isotope ratios.