Shine On You Crazy Diatom

Sometimes the scum of the Earth is filled with inherent beauty. For example, within the slimy, green film that skirts intertidal rocks and gives this aquarium glass a translucent, fluorescent hue, glistens some of the most beautiful and important organisms on Earth-diatoms.

Diatoms are single-celled algae with special cell walls made from silicon dioxide. Viewed under a microscope, the ostensible sludge becomes a collection of minute, sparkling sculptures. Crystalline ridges and ribs, spikes and spines, ornament cylinders and 3D-stars in near-perfect symmetry.

But diatoms provide more than beauty. Like plants, these microscopic protists are photosynthetic and form the base of aquatic food chains. Some species thrive in highly acidic environments, while others prefer deep, cold waters or warm, shallow ones. By studying diatom distributions, scientists can monitor water quality and the effects of pollution, for example, or glean a timeline of climate change from fossilized diatoms.

When diatoms die, they accumulate by the millions on the bottom of lakes and oceans. These deposits are commercially harvested as "diatomaceous earth" and added to a wide range of products from cleaning abrasives to swimming pool filters to cat litter. Not bad, for scum.

Example of apennate, bilateral form of diatom.
Photo: SEM image by Sarah Spaulding

Diatoms are either symmetric bilaterally, the way humans are, or around a central axis, much like a starfish is.
Photo: SEM image of marine diatom by Elizabeth Ruck.
Diatoms proliferate by cell division accompanied by a reduction in size. Once the cells reach a certain size, sexual reproduction (accomplished through meiosis) is induced.