What is a Sediment Trap?

A sediment trap is a type of large container that has been used by scientists since the late 1970s to collect samples of small and large particles falling to the sea floor. The trap acts as a kind of water filter, collecting and storing various particles and elements for analysis by researchers at a later date. Sediment traps provide a wealth of valuable information about the ocean and the sea-life that inhabits it.

There are three types of sediment traps that scientists use: buoyant traps, moored traps and surface traps. A buoyant trap that drifts freely through the ocean water at different depths and is designed to catch sediment drifting in the ocean current. Information about the sediments found in buoyant traps allows researchers to investigate which nutrients and elements create good fishing areas as certain particles are pushed through the current.

A moored sediment trap is tethered to weights on or near the ocean floor, and it collects sediment that gives scientists a greater understanding of how and in what quantities different elements and nutrients reach the plant and fish life near the bottom. Surface traps provide information about how nutrients and elements travel from the surface of the ocean to greater depths and allows for a comparison of surface sediment to floor sediment.

While in the water, a sediment trap must remain in a vertical position in order to work properly. Sediment samples can and do become compromised if the position of the trap is incorrect for an extended period of time. Samples also can be compromised in instances where zooplankton, small living organisms found in ocean water, permeate the sediment trap filter and consume the samples, although this is more common in traps placed closer to the ocean floor.

The length of time that sediment traps remain submerged varies, but most typically remain at a given location for close to a year. Sediment traps are equipped with beacons for recovery purposes and often have other technologies housed in or on the trap itself to provide further information about changes in water conditions or the tilt angle of the trap. Sediment traps are constructed out of titanium, which allows for long-term use and immediate redeployment after collection of samples.