An in situ experimental column for the study of vertical migration in plankton

SUMMARY. 1. An experimental column that can be installed in situ to manipulate the behaviour of planktonic organisms is described. 2. The column incorporates a profiling system for collecting water samples and measuring water temperature, oxygen and underwater light, and can be fitted with a battery‐powered lighting unit for ‘photoperiod’ experiments. 3. Tests showed that this equipment can be rapidly deployed from a small boat to enclose a relatively undisturbed column of water. 4. Experiments with planktonic rotifers showed that the pattern of vertical migration recorded inside the column was very similar to that recorded outside.