ABSTRACT: The chemical and physical (water content) changes in sediment profiles beneath and around fish farm cages were investigated on a seasonal basis in Cephalonia Bay, Greece, a relatively enclosed marine area with weak currents and silty substrate. Thesurface concentrations and the vertical distribution of the sedimentary variables studied (organic matter, organic carbon/nitrogen, chlorophyll, phaeopigments, water content and total phosphorus) varied substantially with distance from the cages and withseason. The black-coloured top layer (farm sediment) showed high concentrations of organic matter, phaeopigments and total phosphorus as well as high water content while the compact subsurface layer had concentrations close to (or lower than) those at thecontrol site. The thickness of the farm sediment layer under the cages varied with season, while in all seasons it decreased rapidly with increasing distance from the cages.