“…So, using classical tissue enrichment factors and average stable isotope values of muscle (δ 13 C = -15.2‰; δ 15 N = 9.4‰) and whole body (δ 13 C and δ 15 N calculated whole body = -16.6 and 8.5‰ respectively), one should expect the isotopic ratios of the filter-feeder's diet to be about -16.2 (muscle) or -17.6‰ A classical mixing model (see Raikow and Hamilton, 2001) could predict that Pecten maximus consume a mixed diet with a minority of phytoplankton, or conversely, that it consume mainly phytoplankton together with a small amount of another food of very enriched δ 13 C value. As in mussels, the P. maximus diet might include dissolved organic carbon (Roditi et al, 2000), deposit material (Raikow and Hamilton, 2001), benthic algae, microheterotrophs and bacteria (Kang et al, 1999;Kreeger and Newell, 2001;Nichols and Garling, 2000). As we did not have stable isotope values of these potential food sources in the Bay of Brest, (but only overall POM) we cannot evaluate the scallop's diet in detail.…”