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Abstract:
An indoors large scale tower-tank system that allows creation of a well controlled vertical stratification of temperature and chemical conditions is described. The system consists of two 11.2 m high stainless steel columns (diameter 86 cm) filled with water from a nearby lake. The temperature control system can maintain any temperature profile with a vertical resolution of 0.5 m. Each column has 23 sampling ports and eight observation windows. Constructional details and maintenance experiences are given. The system provides one with the ability to perform experiments on a large scale which cannot be carried out in the field as climatic conditions cannot be controlled. The design of two typical experiments is described. The first one measures the effect of varying mixing depth on algal competition. The second tests the existence of a chemical cue for the induction of vertical migration of zooplankton.