Monday, March 23, 2009

Diatoms under a Scanning Electron Microscope

This is a colorized scanning electron microscope image of a sample of freshwater diatoms collected from a creek in Pennsylvania. Diatoms are a type of algae and are commonly found growing on the glass of fish tanks. In nature they are the brown coating on rocks in a stream, or any body of water on earth. There are thousands of types of living diatoms and probably millions of types in the fossil record. The diatoms are mainly constructed from silicon dioxide – commonly called quartz by geologists. This very rugged and stable material allows the skeletons of these microscopic animals to become fossils.

It is near impossible to sum up the topic of diatoms in a short space. As a group they have a very rich scientific history as they have shaped both geology and biology studies. Specimens mounted on microscope slides were viewed for entertainment in Victorian England. There is little doubt that their variation in form and shape makes them interesting to study.


Recently I was asked to photograph a large number of microscopic organisms in the modern HDTV format. It has been at least ten years since I photographed many of these species, so it was nice to return with modern cameras and see what I could do. The Vovlox is a favorite of students, looking like a geodesic dome with replicas of itself in side; it is really a form of algae. When students first look at microscopic algae they think it will just be stationary but the opposite is true. Volvox are very fast moving, each of the cells has two tails that help with transportation. The cells all work together in a colony that spins and bumps through the water. Volvox is a freshwater algae.