Aluminum Shadowing–Direct Projection Photomicroscopy of Diatom Frustules

An aluminum shadowing–direct projection method is described which allows high resolution photomicrographic reproduction of diatom preparations in the 200–800× magnification range. The technique is simple and provides an inexpensive alternative to low magnification scanning electron micrographs. While resolution and depth of field are constrained by the limits of conventional optical microscopy, the shadowing technique permits size determination in three dimensions. In addition, routine diatom identification and enumeration can be done directly from photographic prints, which provide a permanent record for storage.Key words: diatom, microscopy, phytoplankton