Invisible World: Diatoms

Diatoms are single-celled organisms that reside in water at the bottom of the food chain. They are tiny and virtually invisible to the naked eye. But what a story they can spin.

The Academy of Natural Sciences of Drexel University has the second-largest collection of diatoms in the world with more than 220,000 slides — each containing hundreds, if not thousands, of diatoms — dating as far back as the 1850s.

In the 1950s, the collection was named the Diatom Herbarium by the Academy’s late environmental scientist Ruth Patrick. Patrick was a world authority on freshwater ecosystems who developed methods to monitor water pollution and its effects on aquatic organisms.

She identified diatoms as key indicators of environmental quality — certain species flourish in certain environmental conditions, so the abundance or lack of a particular species speaks to the health of a waterway.

Today, the Diatom Herbarium is under the care of a group of scientists led by Assistant Curator Marina Potapova, who refers to the tiny organisms as “environmental archives” because the silica skeletons they leave behind inform scientists about the past.

Potapova is in the middle of a multi-year project with more than 50 other international collaborators to build a comprehensive database of diatom flora of the United States, for use in applied research. She is adding species from the existing Diatom Herbarium, as well as those collected in the field, and “bumping into new species all the time” along the way, she says.

Tetracyclus glans gravitates toward cold lakes. This one was collected from an unnamed lake in Russia.

Post by Katie Clark. This article first appeared in EXEL, Drexel University’s research magazine.

To learn more about the Diatom Herbarium and the digitization process, click on this link to the Young Diatomists Blog of the International Society of Diatom Research. 

One comment

  1. Since seeing his first diatom arrangement an intricate pattern of algae crafted by German microscopist J.D. M ller Matthew Killip has been enthralled with the Victorian art form. “I love seeing the hand of man display the work of nature so beautifully,” he says.

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