Target life cycle stage: Veligers
Sampling gear: Standard plankton net (either Student or Wisconsin)
Recommended habitat(s): Nonflowing waters
Type of data collected: Either quantitative or qualitative
Vertical Plankton Tow
Deployment protocol: Using a labeled dropline, lower the net into the water for a known distance. Take care to keep the net vertical and off the bottom. It may be necessary to weight the net to ensure its vertical position in the water column. When the desired depth is reached, pull the net straight up through the water column, rinse the sample down into the collection vessel, drain the net, record the distance, and store the sample for later analysis. Replicate samples are recommended. If possible, 200 L of water should be sampled for each replicate.
Advantages: In deeper habitats, it may be easier to collect quantitative data using this method.
Disadvantages: The net will usually need to be weighted. Care must be taken to keep the net off the bottom and to begin sampling at an appropriate distance (>0.5 m) from the bottom. If sampling is done from a boat, it will need to be stationary to maintain the vertical orientation of the net in the water column.
For information on calculating data retrieved from plankton nets, see Analyzing Plankton Tows, Pumped Samples, and Shallow Water Samples.