A CURRENT-ACTIVATED SEDIMENT TRAP

A current-activated sediment trap is described that collects particles based on preselected cur-rent speed and direction criteria. The colle ctor incorporates a steep-walled funnel, a motor-driven carousel with sample cups, an absolute optical shaft encoder, and an acoustic curren t meter. A field trial of the trap was carried out in a shallow marine embayment over 3 d where it correctly positioned cups in response to tidal changes in current speed and direction. Particle organic content and sedimentation rates calculated over hourly intervals were similar to measurements with a standard sequential sampling trap over several hours when the two traps were deployed simultaneously.