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Marine Ecology Progress Series

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MEPS 387:167-177 (2009)  -  DOI:

Determination of diet in Manila clams by spatial analysis of stable isotopes

C. Dang1,2,*, P. G. Sauriau3, N. Savoye1,2, N. Caill-Milly4, P. Martinez5,6, C. Millaret1,2, J. Haure7, X. de Montaudouin1,2

1Université de Bordeaux and 2CNRS, UMR 5805, Station Marine d’Arcachon, 2 rue du Pr Jolyet, 33120 Arcachon, France
3LIENSs, Université de La Rochelle, CNRS, 2 rue Olympe de Gouge, 17000 La Rochelle, France
4IFREMER, Laboratoire Ressources Halieutiques Aquitaine, 1, allée du parc Montaury, 64600 Anglet, France
5Université de Bordeaux and 6CNRS, UMR 5805, Avenue des Facultés, 33405 Talence, France
7IFREMER, Laboratoire Génétique et Pathologie, Polder des Champs, 85230 Bouin, France

ABSTRACT: Spatial changes in the dietary regime of Ruditapes philippinarum from intertidal sediments of Arcachon Bay were depicted by analyzing stable isotope ratios in both its adductor muscles and potential trophic sources. Manila clams were collected from 50 sites in May to June 2006. Dietary reconstruction was based on the IsoSource mixing model, considering trophic enrichments of 3.5‰ for carbon and 3.0‰ for nitrogen, which were determined experimentally. δ13C and δ15N values, respectively, averaged –28.2 and 5.2‰ for riverine particulate organic matter (POM), –20.6 and 4.7‰ for inner bay phytoplankton, –21.0 and 5.6‰ for outer bay phytoplankton, –16.8 and 4.8‰ for microphytobenthos, –18.4 and 3.9‰ for sedimentary organic matter (SOM) and 11.8 and 4.0‰ for Zostera noltii. Clam muscle δ13C and δ15N values ranged from –20.5 to –16.4‰, and from 7.6 to 9.3‰, respectively. δ15N significantly decreased from southern to northern parts of the bay, while δ13C values increased with tidal elevation. Outer bay phytoplankton was the major diet component of clams. Clams from the southeast mainly incorporated outer bay phytoplankton despite the proximity of the Leyre River, whereas clams from the northwest incorporated approximately equal parts of inner and outer bay phytoplankton, riverine POM, microphytobenthos and SOM. These patterns were consistent with spatial gradients driven by the dominant role of tidal hydrodynamics within the bay and land-use characteristics of the catchment.

KEY WORDS: Ruditapes philippinarum · Muscle · C and N stable isotopes · Trophic sources · Mixing model · Spatial variability · Arcachon Bay · SW France

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Cite this article as: Dang C, Sauriau PG, Savoye N, Caill-Milly N and others (2009) Determination of diet in Manila clams by spatial analysis of stable isotopes. Mar Ecol Prog Ser 387:167-177.

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