Water Collection Techniques

Van Dorn

A Van Dorn is a water collection device that is used to collect samples for primary production, water chemistry, and ciliate and rotifer analysis. Plugs are pulled against the tube housing by an elastic rubber tube and then held open by loops of metal cable attached to a trigger mechanism. Once triggered, the plugs snap back into place, sealing the tube and capturing the water from that depth. Van Dorns come in various sizes, capturing different volumes. The Van Dorn is used as a primary collection device, immediately to be poured into secondary containers that return to the lab for the various analyses.

Schindler Trap

A Schindler Trap consists of a clear box with hinged top and bottom. Water flows through as it decends and the top and bottom close as it reaches the desired depth and drawn upward. This prevents further water from entering or leaving and retains a sample of known volume.

Schindler Traps are mainly used to sample for zooplankton collection, as the volume enables the researcher to count the number of zooplankton per unit volume. The enclosure is made of clear material to minimize the visual effect of agile species.