Jim Price (left) and Jim Valdes with a prototype of the neutrally buoyant sediment trap. The four small plastic tubes collect sediment and the large central tube houses electronics, a variable displacement device, recovery beacons, and batteries.
A record of pressure measured by a neutrally buoyant sediment trap during a three day-long deployment. The trap is passive for the first three hours after launch, and then begins to check and correct depth at hourly intervals. This instrument was targeted for 150 meters depth, and was slightly heavy as it was launched. At hour four it rose to the target depth by increasing its displacement slightly. It then remained within about 10 meters of its target depth until the end of its mission.
Particle flux scientists employ three main sediment trap designs. The cylindrical, surface-tethered and free-drifting neutrally buoyant traps serve in shallow waters, and the moored conical traps are used for deep waters (drawings are not to scale). Given the generally decreased particle flux at great depths (see graph at left in the figure), the deep traps' conical shape increases the collection area--these traps have a 300 times larger collection area than the shallow water traps.