The role of epiphytes in an intertidal Zostera noltii seagrass bed in Marennes-Oléron Bay was assessed in comparison with the other main benthic primary producers (Z. noltii, microphytobenthos) at two bathymetric levels and on a seasonal basis. Assemblage and biomass of epiphytes were studied using Scanning Electron Microscopy (SEM). Zostera noltii and its detrital matter followed a typical seasonal pattern: microphytobenthos was present in large quantities throughout the year representing 21 % of the total biomass while detrital matter, above-ground parts and below-ground parts accounted for 65, 9 and 5% respectively. Only two species of epiphytic diatoms, Cocconeis scutellum and Cocconeis placentula, were 2 observed on seagrass leaves. Epiphyte biomass was very low, representing on average less than 0.001 % of that of microphytobenthos or leaves. This low epiphyte biomass is linked with the absence of macroalgae and also with the low biovolume of Cocconeis, which formed a monolayer of cells on leaves. This can be explained by the severe conditions of the intertidal and the high leaf turn-over of Zostera noltii leaves.