A while back I wrote a diary on microorganisms with a brief mention and several photographs of diatoms. Diatoms are major players in net primary production and sequestering of Carbon. Not least, these remarkable protists as photosynthetic organisms are huge releasers of oxygen (estimated at 20-40% of all oxygen on the planet!) and thus our ability to have breathable air (at least every fifth breath is provided by diatoms!) Other players include cyanobacteria, other "algae" and the terrestrial forests in the tropics and Siberian taiga, plus the other forests. Another bacterium is thought to be the source of the chloroplastid (which is more brownish than usual) found inside each diatom frustule (or shell), which is made of glass and water, in effect opal - SiO2+H20. Each shell has numerous pores which allow gas exchange. The ability to make glass houses is shared by only a relatively few organisms, including radiolarians, glass sponges and silicoflagellates. Most skeletons of other organisms are made from calcium salts, cellulose or chiton.
The pore patterns and shapes of diatoms make them among the most beautiful of microorganisms. Not only do we have numerous living species, but one fossil area alone, the Oamaru Eocene-Oligocene beds in New Zealand, contains around 700 species. Other fossil diatomite is found in Russia, Ireland, California, Maryland and many other localities. The Oamaru sites are especially interesting as they were laid down during the runaway greenhouse of the Paleocene to the Oligocene, when the planet had no ice (things started to cool toward the end of the Eocene and continued to do so fairly steadily into the Pleistocene.) One apparent occurrence during such a warm period is an increase in the rate of speciation and indeed this seems to be so in regard to these amazing photosynthetic microorganisms, few of which reach up to 500 microns, or half a millimeter.
The study of diatoms was one of the favorite natural history pastimes during the late Victorian period and there were numerous mounters of these little gems up until the mid Twentieth Century, with only a handful left in modern times, mainly in Europe. One of the great mounters of diatoms was the German Johann Diedrich Möller, who founded a slide-making company that lasted up into the mid Twentieth Century. He was famous for his type slides, some of at least 400 species mounted by hand! He also arranged diatoms into patterns, sometimes using well over 1000 individual diatoms. Another German, Adolf Schmidt, whose Atlas der Diatomaceenkunde, is still useful today and was continued by later researchers after World War II, was prominent in the field. Many British mounters and some French are also known, and their antique slides are still on the market, some for fairly high prices. Below are a few photos of diatoms on a Möller type slide.
One of a series of diatoms on a Möller type slide. This is an Aulacodiscus
Two more diatoms on the same type slide.
Women took up the speciality, especially after 1900, and today there are a number of women involved and several of the major works on North American species were written or co-written by women.
Despite their small size diatoms are vital to our survival and we would do well not to ignore them. The fate of the oceans and freshwater and saltwater lakes, rivers and creeks will determine their survival, as well as our own. The number of modern species of diatoms alone is great - over 20,000 and maybe more than a million (microorganisms are very poorly known even with all the research over the last few hundred years since the invention of the light microscope.)
The following are a series of mostly fossil species which I photographed using a trinocular phase contrast microscope. Most are in the 50-200 micron range.
A large recent diatom from McMurdo Sound, Antarctica.
Briggera capitata from the Eocene-Oligocene of Oamaru, New Zealand.
Biddulphia capusina from the Eocene-Oligocene of Oamaru, New Zealand.
Aulacodiscus janischii from the Eocene-Oligocene of Oamaru, New Zealand.
Brightwellia coronata, a very rare species, from the Eocene-Oligocene of Oamaru, New Zealand.
Triceratium favus var. quadrata from the Eocene-Oligocene of Oamaru, New Zealand.
Fossil centric diatom from Japan.
A few references:
Mann, David G. Diatoms http://tolweb.org/...
Plankton Chronicles: Diatoms http://www.planktonchronicles.org/...
Schmidt, A. and others 1874 - Atlas der Diatomaceenkunde. Example https://archive.org/...
What are Diatoms? http://westerndiatoms.colorado.edu/...