In Arcachon Bay, the intertidal area is mainly occupied by sandbanks, oyster parks and seagrass beds. The aim of this study was to estimate the meiofaunal contribution to the trophic systems of these biotopes. Seven stations from the inlet to the inside of the bay have been studied seasonally during the year 1986. Meiofaunal stratification presents different patterns according to the facies but 75 % to 90 % of the total abundance is restricted to the top cm in all the stations. The meiofauna, strongly dominated by Nematodes (> 75 %), shows a noticeable temporal stability through the year: meiofaunal communities of low density and diversity dominated by omnivorous-predatory Nematodes characterize the open sea sandy stations with low detritus content; on the contrary, the sheltered seagrass and oyster park stations with high organic carbon content have communities of high density and diversity, dominated by deposit and epistrate feeders. From a comparison of the meiofaunal and microphytobenthic biomasses and associated productions, meiofauna is suspected to consume an important part of the yearly benthic primary production: 60 % in sandbanks, 42 % in oyster parks and 76 % in seagrass beds. When the needs of macrofauna are taken into account, it seems unlikely that the primary production can sustain the benthic secondary production, particularly in seagrass bed and oyster park sediments. In these areas, the high content of detrital organic carbon (130 g C mP2) constitutes a substitute food source for meiofauna as well as for macrofauna.