Seasonal dynamics of trophic relationships among co-occurring suspension-feeders in two shellfish culture dominated ecosystems

• Published in: Estuarine, coastal and shelf science coastal and shelf science, 2009-04, Vol.82 (3), p.415-425
• Main Authors: Lefebvre, Sébastien, Marín Leal, Julio César, Dubois, Stanislas, Orvain, Francis, Blin, Jean-Louis, Bataillé, Marie-Paule, Ourry, Alain, Galois, Robert
• Format: Article
• Language: English
• Subjects: Alveolata; Animal and plant ecology; Animal, plant and microbial ecology; aquaculture; Biological and medical sciences; Brackish; Brackish water ecosystems; Cerastoderma edule; Crassostrea gigas; Crepidula fornicata; feeding; food web; France, Normandy, Baie des Veys; Fundamental and applied biological sciences. Psychology; General aspects; Lanice conchilega; Marine; Mytilus edulis; plankton; potential competition; Sabellaria alveolata; stable isotopes; Synecology
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2009.02.002

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 δ 13C and δ 15N 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.