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The planktonic diatoms, Asterionella formosu Kutz. and Synedru acus Hass., were cultivated in 96-well flat-bottom plastic plates with 100 pL of medium per well. At regular time intervals, cells were counted using an inverted microscope. Typically, the number of cells per well increased over 10 days from 50-200 to >1000. The first growth inhibition experiments were successfully run at room temperature using natural illumination. However, for better control of the growth conditions, a special micro-incubator was manufactured. This device hosted two incubation plates and was equipped with Peltier elements for cooling below room temperature, and a small luminescent lamp. For automatic counting, two digital micro-photographs of each well were taken, first at a 0.2 msec exposure and the second at a 5 msec exposure. The images were treated by means of custom software based on ImagePro to identify and count the diatom cells. Cultivation of diatoms on the micro-scale proved to be a convenient technique. Using this technique, we were able to study the effects of mercaptoethanol, Cu2+ on A. formosa and Cu2+, Hg2+, Cd2* and phenanthroline upon the growth of S. ucus.

No abstract