The volume of plankton can be determined by settling. The preserved plankton sample is allowed to settle in a graduated cylinder. The results obtained using this method have some inherent inaccuracies. Nevertheless, the technique gives some idea of plankton abundance and is useful for comparing plankton densities in various areas. It is also simple and fast.

Plankton sample (preserved in 3-5% formalin), graduated cylinder (size depends on sample size)

1. Pour the sample into the graduated cylinder and let the sample settle for at least an hour.

2. Read and record the volume of the plankton settled (in millimeters)_______ millimeters of plankton.

3. Plankton abundance may be calculated by dividing the volume of plankton in millimeters by the volume of water sampled in cubic meters:

Plankton abundance = volume of plankton

volume of water sampled

Calculate and record the plankton abundance for your sample:

Plankton = Volume of plankton =

abundance volume of water sampled

Plankton abundance = _____________________ ml/ M³