Seasonal dynamics of trophic relationships among co-occurring suspension-feeders in two shellfish culture dominated ecosystems |
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| Authors: | Sébastien Lefebvre Julio César Marín Leal Stanislas Dubois Francis Orvain Jean-Louis Blin Marie-Paule Bataillé Alain Ourry Robert Galois |
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| Institution: | 1. UMR 100 IFREMER-Université de Caen Basse-Normandie “Physiologie et Ecophysiologie des Mollusques Marins (PE2M)”, Laboratoire de Biologie et Biotechnologies Marines, IBFA, IFR ICORE 146, Esplanade de la Paix, B.P. 5186, 14032 Caen Cedex, France;2. Departamento de Ingeniería Sanitaria y Ambiental, Escuela de Ingeniería Civil, Facultad de Ingeniería, La Universidad del Zulia, Apartado Postal 526, Maracaibo 4001-A, Estado Zulia, Venezuela;3. LIENSs, UMR 6250 CNRS – Université de La Rochelle, 2 rue Olympe de Gouges, 17042 La Rochelle Cedex, France;4. Syndicat Mixte pour l''Équipement du Littoral (SMEL), 50560 Blainville sur Mer, France;5. UMR 950 INRA-Université de Caen Basse-Normandie “Écophysiologie Végétale, Agronomie et Nutrition N.C.S. (EVA)”, Esplanade de la Paix, B.P. 5186, 14032 Caen Cedex, France |
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| Abstract: | The temporal dynamics of carbon and nitrogen isotope values of co-occurring suspension-feeders in two shellfish culture areas (Normandy, France) were investigated over two years to evaluate the inter-specific trophic partitioning and relative contributions of organic matter sources to benthic suspension-feeders' diet. Oysters (Crassostrea gigas), mussels (Mytilus edulis), cockles (Cerastoderma edule), slipper limpets (Crepidula fornicata), and sand-mason worms (Lanice conchilega) were sampled in an estuarine environment (Baie des Veys, east Cotentin, Normandy), while oysters, mussels, slipper limpets, and honeycomb worms (Sabellaria alveolata) were sampled in an open-marine environment (Lingreville-sur-mer, west Cotentin, Normandy). Whatever the sampling period, the bivalves, C. gigas and M. edulis, exhibited the lowest values of δ13C and δ15N compared with the other species. Feeding relationships among suspension-feeders in both C. gigas culture areas exhibited temporal variations due to the marine/estuarine influence and seasonal changes in food supply. In the open-marine ecosystem, the contribution of phytoplankton remained the most important for all species except S. alveolata, while in the estuarine ecosystem, microphytobenthos and/or macroalgae detritus contributed a larger extent to the organisms' diets. During phytoplankton bloom periods (e.g. May and July) suspension-feeders, except for S. alveolata, relied strongly on phytoplankton; however, the majority of suspension-feeders exhibited different opportunistic behaviour in winter when phytoplankton biomass might be a limiting factor. We hypothesized that differences in particle capture and selection by the suspension-feeders influenced their isotopic values. Feeding ecology of suspension-feeders partly explained why competition was limited and why ecosystems can often support unexpectedly large numbers of suspension-feeders. We also showed that understanding ecosystem characteristics of the organic matter sources is of primary importance to determine the extent to which members of the suspension-feeding guild potentially compete for food. |
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| Keywords: | aquaculture plankton Crassostrea gigas feeding food web potential competition stable isotopes France Normandy Baie des Veys |
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