We report results from free-drifting sediment trap deployments at 200 m depth which enable measurement of the diel variations in the downward flux of detrital particulate dimethylsulphoniopropionate (DMSPp) over periods of 24-72 hours in three contrasting trophic regimes of the tropical northeastern Atlantic Ocean off Mauritania. The source of DMSPp was the phytoplankton living in surficial water layers. The three regimes exhibited similar strong diel cycles, the nocturnal fluxes being up to 100-fold lower than the daytime fluxes. High (or low) detrital DMSPp, fluxes were associated with high (or low) numbers of pteropods trapped inside the sampling cups. Thus, contamination of sinking material is likely to have occurred, promoting an overestimate of the daytime fluxes. It is concluded that the transport of DMSPp at depths deeper than 200 m is strongly influenced by the downward migration of pteropods during the daylight: hours. This mode of transport is shown to be a general process in tropical waters for accelerating DMSPp sedimentation. Under these oceanic and experimental conditions the daily DMSPp flux at 200 m accounted for only about 0.1 % of the DMSPp standing stock. Hence, the DMSPp downward flux is likely to have a minor influence in the upper ocean budget of DMSPp.