Plankton Nets

The plankton net or sampler is a device that makes it possible to collect both phytoplankton and zooplankton samples. For quantitative comparisons of different samples, some nets have a flow meter used to determine the amount of water passing through the collecting net.

The plankton net or sampler provides a means of obtaining samples of plankton from various depths so that distribution patterns can be studied. Quantitative determinations can be made by considering the depth of the water column that is sampled. The net can be towed to sample plankton at a single depth (horizontal tow) or lowered down into the water to sample the water column (vertical tow). Another possibility is oblique tows where the net is lowered to a predetermined depth and raised at a constant rate as the vessel moves forward.

On the R/V New Horizon they will be deploying the MOCNESS plankton net system (Multiple Opening/ Closing Net and Environmental Sampling System).  The MOCNESS is lowered into the water and towed behind the ship at a speed of about 1.5 knots. There are nine nets, each of which is controlled by a computer in the ship's lab. One at a time, the nets are opened and closed at desired depths, according to what the scientists want to measure. Instruments at the top of the frame help control the nets, and also report depth, salinity, temperature, chlorophyll fluorescence (a measure of phytoplankton in the water), and flow into the nets.

These photos show the MOCNESS ready to go on the the New Horizon July 30, 2002.