An inexpensive device for sampling large volumes of lake water from discrete depths

SUMMARY 1. A sampler was developed that displaces surface water which is replaced with water from a sampling tube at a set depth.
2. The displacement sampler is inexpensive, easy to build, and is capable of collecting water at 7.5 I min⁻¹.
3. Phytoplankton photosynthesis was higher in water from the displacement sampler than in water collected with a Van-Dorn bottle. Subsequent experiments indicated this was due to inhibition caused by the Van-Dorn bottle.