
09/07/2025
Mussels: The River’s Silent Engineers
By K. Brad Barfield
When you stoop on an Ashley County sandbar and pick up a “black mussel” shell, you’re holding more than just a relic of yesterday’s river. You’re touching a living system—one that has been at work for tens of millions of years. Freshwater mussels are some of the most quietly influential engineers in Arkansas’s rivers, shaping the very water we depend on.
What does a mussel do? The answer lies in its method: filtering. Each mussel, half-buried in sand or mud, opens its shell and siphons river water in through one tube (the incurrent siphon), then expels it through another (the excurrent siphon). While inside, the water is sieved by gills—gills adapted not only for breathing but for straining out plankton, bacteria, algae, and suspended organic particles. What comes out is clearer, cleaner water.
A single adult mussel can filter anywhere from 10 to 20 gallons of water per day. In a healthy river, thousands upon thousands of mussels may carpet a single sandbar, filtering millions of gallons daily. Collectively, they are a living purification system—removing silt, excess nutrients, and even heavy metals or bacteria from the flow. It’s not just “cleaning,” either; this filtration creates zones of clarity where fish can hunt and aquatic plants can photosynthesize.
But their work goes even deeper. Mussels cycle nutrients, making food available to other river life. As they feed, their waste products enrich the sediment, feeding bacteria and micro-invertebrates—the base of the aquatic food web. The shells themselves become habitat: after a mussel dies, its shell may shelter small fish, crayfish, or even the next generation of baby mussels.
Now zoom out to the “mussel bed”—a multi-species community, rooted for centuries in the same spot. Mussels anchor the bottom, slow the current, and even stabilize riverbanks, resisting erosion. In ancient times, a single mussel bed could stretch for miles, home to dozens of species. These beds acted as natural water treatment plants long before towns or levees were built.
How long have they been doing this work? Fossils of the Unionidae family date back more than 60 million years, their basic design nearly unchanged. The same species now found in Bayou Bartholomew and the Saline River are virtual “living fossils,” descendants of a lineage older than the Ouachita Mountains themselves.
So the next time you wade the Saline or Bayou Bartholomew and see those dark shells half-buried in gravel, remember: you’re not just looking at the past, you’re seeing the ancient, ongoing labor of the river’s oldest engineers—creatures whose quiet work supports everything else that lives in these waters.
Sources:
This essay is based on the following works, all of which we found in the Ovid T. Switzer, Jr. Collection, of which we have on loan:
Bayou Bartholomew: A Regional Stream, by Clifton L. Birch (1999, C. Birch Publishing)
Bayou D’Arbonne Swamp: A Naturalist’s Memoir of Place, by Kelby Ouchley (2022, LSU Press)
Arkansas: A Narrative History, by Jeannie M. Whayne, Thomas A. DeBlack, George Sabo III, and Morris S. Arnold (2013, University of Arkansas Press)
The Ashley County Eagle archive
U.S. Fish & Wildlife Service and Arkansas Game & Fish Commission reports
Local oral histories and archival material
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