The planktonic diatoms, Asterionella formosa Kutz. and Synedra acus Hass., were cultivatedin 96-well flat-bottom plastic plates with 100 uL of medium per well. At regular timeintervals, cells were counted using an inverted microscope. Typically, the number of cellsper well increased over 10 days from 50-200 to >1000. The first growth inhibitionexperiments were successfully run at room temperature using natural illumination. However,for better control of the growth conditions, a special micro-incubator was manufactured. Thisdevice hosted two incubation plates and was equipped with Peltier elements for coolingbelow room temperature, and a small luminescent lamp. For automatic counting, two digitalmicro-photographs of each well were taken, first at a 0.2 msec exposure and the second at a5 msec exposure. The images were treated by means of custom software based on ImageProto identify and count the diatom cells. Cultivation of diatoms on the micro-scale proved to bea convenient technique. Using this technique, we were able to study the effects ofmercaptoethanol, Cu~(2+) on A. formosa and Cu~(2+), Hg~(2+), Cd~(2+) and phenanthroline upon thegrowth of S. acus.
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