Stable isotopes (delta C-13, delta N-15) and modelling as tools to estimate the trophic ecology of cultivated oysters in two contrasting environments
|Author(s)||Leal J1, 2, Dubois Stanislas1, Orvain Francis1, Galois Robert3, Blin J4, Ropert Michel5, Bataille M6, Ourry A6, Lefebvre S1|
|Affiliation(s)||1 : Univ Caen Basse Normandie Physiol & Ecophysiol Mo, IFREMER, Lab Biol & Biotechnol Marines, UMR 100, F-14032 Caen, France.
2 : La Univ Zulia, Fac Ingn, Escuela Ingn Civil, Dept Ingn Sanitaria & Ambiental, Estado Zulia, Venezuela.
3 : Univ La Rochelle, IFREMER, CNRS, CRELA,UMR 6217, F-17137 Lhoumeau, France.
4 : SMEL, F-50560 Blainville Sur Mer, France.
5 : IFREMER, Lab Environm Ressources Normandie, F-14520 Port En Bessin, France.
6 : Univ Caen Basse Normandie Ecophysiol Vegetale Agr, INRA, UMR 950, F-14032 Caen, France.
|Source||Marine Biology (0025-3162) (Springer), 2008-02 , Vol. 153 , N. 4 , P. 673-688|
|WOS© Times Cited||58|
|Abstract||Food sources for cultivated marine bivalves generally are not well identified, although they are essential for a better understanding of coastal ecosystems and for the sustainability of shellfish farming activities. In addition to phytoplankton, other organic matter sources (OMS), such as microphytobenthos and detritus (of terrestrial or marine origins), can contribute significantly to the growth of marine bivalves. The aim of this study was to identify the potential food sources and to estimate their contributions to the growth of the Pacific oyster (Crassostrea gigas) in two contrasting trophic environments of Normandy (France): the Baie des Veys (BDV) and the Lingreville area (LIN). Two sites were studied in the BDV area (BDV-S and BDV-N) and one in the LIN area. To estimate the contribution of each type of OMS, we used a combination of stable natural isotope composition (delta C-13, delta N-15) analysis of OMS and oyster tissue together with a modelling exercise. Field sampling was conducted every 2 months over 1 year. The sampled sources were suspended particulate organic matter from marine (PhyOM) and terrestrial (TOM) origins, microphytobenthos (MPB), detrital organic matter from the superficial sediment (SOM), and macroalgae (Ulva sp., ULV). A statistical mixing model coupled to a bioenergetic model was used to calculate the contributions of each different source at different seasons. Results showed that isotopic composition of the animal flesh varied with respect to the potential OMS over the year within each ecosystem. Significant differences were also observed among the three locations. For instance, the delta C-13 and delta N-15 values of the oysters ranged from -20.0 to -19.1 parts per thousand and from 6.9 to 10.8 parts per thousand at BDV-S, from -19.4 to -18.1 parts per thousand and from 6.4 to 10.0 parts per thousand at BDV-N, and from -21.8 to -19.4 parts per thousand and from 6.3 to 8.3 parts per thousand at LIN. The contributions of the different sources to oyster growth differed depending on the ecosystem and on the period of the year. Phytoplankton (PhyOM) predominated as the principal food source for oysters (particularly in the LIN location). MPB, TOM, and ULV detritus also possibly contributed to oysters' diet during summer and autumn at the BDV-S and BDV-N sites. SOM was not considered an OMS because it was already a mix of the other four OMS, but rather a trophic reservoir that potentially mirrored the trophic functioning of marine ecosystems.|