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“Have you thanked a diatom today?”

This 1970s slogan circulated among members of the scientific community who pay homage to the value and contribution of the many species of microscopic diatoms.

This article will explain what a diatom is and why we ought to be thankful diatoms exist. It will also explain what diatoms tell us about the Cedar River, and recognize the efforts of a local scientist who has devoted his academic career to understanding diatoms.

What is a diatom?

The diatom is a single celled type of golden brown algae. Diatoms are jewel-like with a tough outer cell made of glass-like silica.

Like snowflakes, diatoms are natural, beautiful, and symmetrical. The similarities seem to stop there. Diatoms are colorful, tinier, and far more durable than snowflakes. For their size, they are stronger than steel.

Classified by shape, diatoms likely evolved before dinosaurs and are encased in the planet’s fossil record. Diatoms live in oceans, freshwater, and damp places. They are efficient little buggers, storing solar energy in the form of high energy oil instead of starch. Diatoms are the basis of both marine and freshwater food chains.

Dr. Main studies Cedar River diatoms

“The reason fish taste fishy is because diatoms produce the Omega 3 oils that fish are known for,” says biologist and Wartburg emeritus professor Stephen P. Main who quite accidentally began his Ph.D. studies studying diatoms on ocean kelp or seaweed.

Mention the word ‘diatom’ and Dr. Main’s face lights up. Main and wife Elaine have made Waverly their home since 1972. Far from those Pacific Coast waters, Dr. Main applied his research to study the Cedar River’s diatoms. It’s taken a lifetime of record keeping to begin to understand that slice of life he examines under the microscope.

“Diatoms secrete a slippery mucilage or slime on rocks and river bottoms that is often brownish. That brown slime is alive,” Main explains.

Diatoms deserve gratitude. Not only are they the foundation of aquatic food chains, but these single-celled algae capture solar energy and photosynthesize, producing 20% of what we breathe. Diatoms also provide a fossil record, recording floods and our planet’s changes over time.

In the future, diatoms may be used in biotechnology. Diatoms could be genetically programed to make material for computer chips. “Diatoms could do this more efficiently and without producing industrial waste,” Main says.

Main presented to a study session of the Waverly City Council on Sept. 23 (Oct. 1 Bremer County Independent) as a representative of the Upper Cedar Watershed Management Improvement Authority. That group has advisory power only. At that presentation Main advised that created wetlands are an effective method of nitrate reduction.

With high water levels and air and water temperatures hovering around the freezing point, Main cautiously stepped into the fast flowing main channel of the Cedar River. Brookwood Park near the Green Bridge has been his sampling site for over 40 years. Main also took samples from the eddies or slow-moving water that sides a river naturally.

So what happens when a river is channelized or straightened?

There are fewer diatoms, and less nutrition for fish and other species up the food chain. Like wetlands, an eddy houses a greater quantity and more diversity of diatom species.

Diatoms attach to submerged surfaces, like the rock we turned over in an eddy. Dr. Main collected diatoms. Other living things wriggled about, still active in freezing water.

Like many species abundance, diversity and adaptation are keys to success. A hundred species of diatoms make their homes in the Cedar River.

“Diatoms continue to respond to their environments. They are dynamic. As the volume of water in the Cedar River has increased, water temperatures vary less. Diatoms used to be seasonally reduced,” says Main, explaining that the Cedar River once experienced a spring and fall “bloom” of diatoms. Now, they grow all summer.

Is that a good thing?

“Diatoms provide food for mussels and insects. As they multiply, responding to nutrients like nitrates and phosphates, they also die and decompose. That uses up oxygen in the water and contributes to the Dead Zone in areas like the Gulf of Mexico,” Main says.

On this wintry day, the water of the Cedar River showed little turbidity. That is, the water was quite clear. (See photo) A 2013-2015 study of Main’s correlated diatoms and turbidity. As river turbidity increased, there were fewer diatoms.

With the humility of a true scientist, Main admits that there is more that is unknown than what humans know. Today, there are only a couple hundred American scientists studying the diatom, and Main is one of just three in Iowa. He continues to study Cedar River diatoms and unlock their secrets.