Despite their small size, foraminifera often reach high standing stocks and play a significant role in structuring the top layers of the sediment. However, the behavioral and ecological interactions of foraminifera with the surrounding sediments have been rarely investigated. In order to study these poorly known aspects of foraminiferal ecology, living foraminifera from bathyal and shallower water depths were successfully maintained in microcosms and their relationship with the sediment was investigated. Sediment-interactions of foraminifera take part mainly as a result of 1) locomotion, 2) deposit feeding with ingestion and egestion within different sediment layers, thus causing constant bioturbation, and 3) the use of particles for the formation of cysts for feeding, reproduction, chamber building or protection. Movement by foraminifera results in the ventilation of the sea floor as demonstrated by the active and passive transport of luminescent particles. From the experiment conducted, a high mixing rate (Db ≈ 0.2 cm 2/day) for the foraminiferal assemblage was calculated. Thus, benthic foraminifera contribute significantly to the bioturbation of surface sediments. These observations are discussed in relation to microhabitats and the fate of organic matter at and below the sediment-water interface.