Abstract.An intertidal mud sediment in the Kerguelen Archipelago was sampled weekly from January 1982 to March 1983. Measurements were taken for organic matter (carbon and nitrogen) and biological (bacteria, microphytobenthos, and mciofauna) parameters. The sediment is rich in organic matter, with a mean organic carbon content of 130gC‐ m‐2. Benthic living components yield low mean biomasscs in relation to the total organic pool. Besides some marine inputs, the main allochthonous source was identified as terrestrial inputs. Benthic activities seemed strongly governed by food availability and not by temperature. Obvious seasonal changes in bacterial abundances (direct counts), primary production, and mciofauna distributions were observed. Photosynthctic production reached high values (up to 2275 mg C‐m‐2‐d‐1), reflecting the presence of a dense microphytobenthos. Preliminary energy budgets for two seasons (spring and winter) have been constructed. In both periods, the measured primary production can support the high mciofauna