Sediment trap

Sediment traps are instruments used in oceanography and limnology to measure the quantity of sinking particulate organic (and inorganic) material in aquatic systems, usually oceans, lakes, or reservoirs.

[1] Sediments traps normally consist of an upward-facing funnel that directs sinking particulate matter (e.g. marine snow) towards a mechanism for collection and preservation.

Typically, traps operate over an extended period of time (weeks to months) and their collection mechanisms may consist of a series of sampling vessels that are cycled through to allow the trap to record the changes in sinking flux with time (for instance, across a seasonal cycle).

Preservation of collected material is necessary because of these long deployments, and prevents sample decomposition and its consumption by zooplankton "swimmers".

Lagrangian traps must surface at a predetermined time, and report their position (usually via satellite) in order to be recovered.

Model of a sediment trap : It mainly consists of a huge funnel , a ring of Glass floats (3 are visible) and a revolving wheel with sample bottles.
Sediment trap deployment in Thermaikos Gulf, Greece, 2000. The sediment trap has H/D 5.5, internal diameter 127 mm, and a net at the top. The sediment trap had been cast at 25-30 m depth and 3 m above seabed. The anchor (chain) of the mooring can also be seen.