Life at River Bottom
A freshwater mussel groupie ponders what the loss of these mollusks means for humans and wildlife
On a March day in 2009, nine years after Chewacla Creek dried up, I stood in the roadside weeds near a county road bridge in Alabama. The creek – the city of Auburn’s water supply – was flowing again, thanks to legal protection. I was wiggling first my legs, then my arms, into a borrowed wet suit. I left it unzipped while I bent over, one hand on the truck’s tailgate for balance. My other hand reached to shoehorn my sneakers over neoprene booties. I straightened, returning my attention to the zipper. It gaped like an open shell, displaying my pregnant belly, almost four months round. With effort, I zipped up the two halves, encasing myself. My first child would dangle below me while I snorkeled – something I’d never done before.
illustration Josée Bisaillon / joseebisaillon.com
I had joined this Auburn University crew of freshwater biologists on a whim, based on a last-minute invitation. One these biologists was my husband, Andrew. We thrashed along, dropping down a steep bank, departing the road where it headed over the bridge. Stepping into the creek, we spread out and moved upstream, away from the bridge where we had parked the truck. I sank to my knees, letting cool water flow over my thighs. It was shallower than a bathtub. When I eased forward onto my hands, the water didn’t even cover my back. Biting the snorkel mouthpiece, I submerged my head through a layer of crisp-edged leaves and into another world.
A fish darted close. Its gills clapped against its head as if it was slowly applauding my green-rimmed face. The creek filled my wet suit and filled my ears, dimming other sounds, gurgling through my head like a pitcher pouring into an endless glass. I reveled in the bright underwater world, delighting at each colorful darter slipping in and out of view. Sediment stayed on the creekbed, leaving the water clear until my fingers swept the rocks, raising a cloud. I grazed my belly upstream into better visibility, moving slowly to the rhythm of my breath whooshing up and down my snorkel.
Months later, when I learned the word for this creekbed world – benthos – I would remember each curled snail and crayfish scooting backward.
Then I lifted my head and realized I had fallen well behind the others. I slurped myself to a standing position and waded toward the bank. They had told me that the creek’s edges often held many hidden freshwater mussels. Finding those mussels was our purpose for snorkeling Chewacla Creek in March.
Look for two small openings, they told me. Like two short tubes often sticking up just a bit from the mud. “Once you get your search image, it’s easy,” Professor Jim Stoeckel, a compact man who rarely stood still, assured me from across the creek. “You’ll really start seeing mussels.”
After about an hour, the extent of Stoeckel’s optimism became apparent. I had plucked and flipped and groped at least fifty rocks, leaves, twigs, and lumps in the mud. I’d never seen a mussel in the wild. My search image, which resembled two short drinking straws poking out of the mud, wavered like a mirage.
I refocused, remembering photos I’d seen, and tried to imagine our quarry. These are not the coal-black ocean mollusks clinging like butterflies to rocks or jumbled on plates under decadent sauces. Neither are they the notorious zebra mussels, Dreissena polymorpha, invasive species plaguing rivers and lakes north of here. The family Unionidae, native freshwater mussels, lives in creeks and rivers and includes almost three hundred species in North America. Nearly 70 percent of them are imperiled.
These freshwater mussels live mostly buried. Their shell edges are parted like a surprised gasp, exposing two apertures. One intakes and the other releases water, which is how mussels eat, breathe, and even gather sperm to meet their eggs. Those apertures actually look like Georgia O’Keefe paintings – flowers, female anatomy – elegant ovals decorated with variously shaped and colored papillae. Apertures, papillae, curve of a shell. This is our search image.
Although I did not see her, a mussel was there, near my feet. Sometimes, sidling along with one meaty foot, this mussel would leave a trail, but now she nestled into sandy clay. Above this mussel, water flowed. We stood in our wet suits, leaning toward the creekbank. Andrew pointed; I struggled to see what he described. Between my protruding abdomen and taut wet suit, I couldn’t bend my waist, so I bent my knees and tipped forward.
“She’s displaying,” he told me. He waited while I stared.
Mussels’ peril is our own. We need the same thing – plentiful clean water.
Then the mussel seemed to materialize, differentiating from the leaves and rocks. Before my eyes, the creek bottom gained a dimension as I perceived its complexity. A little spectaclecase, Villosa lienosa, was doing the work of a freshwater mussel – filtering. She was also doing the work of many females this time of year – displaying. Her gills bulged with offspring that she’d brooded for months. Now the time had come. Above those offspring waved her mantle lure, decorated with multiple tentacles that looked like a clump of small black worms. The bait.
Ripe with progeny, the female mussel must attract a fish to deliver her babies into the world. Striking the bait, a fish will release thousands of these larval mussels, which will hitch a ride on the fish’s gills, transforming into independent juveniles and then letting go and sinking into their new creekbed lives. I was impressed. Delivering offspring into the world clearly demanded heroic efforts.
Watching a wild mussel display her lure opened a door in my mind, like my first kiss. I became a freshwater mussel groupie. I fawned over their photographs, mussels ranging in size from thumbnail to dinner plate, building glassy or ridged or pimpled shells that are brown or black or yellow, with or without dark stripes fanning across them, and always paved inside with pearl – white, pink, deep violet. I stalked them from a distance, writing their names in my notebooks: fatmucket, pistolgrip, heelsplitter, shinyrayed pocketbook, spectaclecase, pigtoe, snuffbox. I pored over their bios. Posters of mussels hung in our bedroom.
Freshwater mussels are old. As a group, they have persisted and adapted across, some scientists estimate, around five hundred million years. Mussels share a family-tree branch with other mollusks. Their phylum, Mollusca, includes snails and slugs, squids and octopus, and clams and scallops, to name a few. Their class, Bivalvia, notably features multitasking gills. These versatile organs help with respiration, excretion, and reproduction. Breathing, defecating, and making babies all coincide in one efficient organ.
Mussels’ finest ecosystem service is filtration, not unlike the fuel filter in an engine. Sift out the extra stuff – eat some, package some for deposit in the substrate – and leave the water cleaner. An assembly of mussels can filter from 10 to 100 percent of water in a creek or river section each day, depending on the density of mussels and flow of water. The water flowing in Alabama’s creeks and rivers, the water sitting in catfish ponds and reservoirs, the water gushing from my own faucet has probably passed through the interiors of freshwater mussels. As they filter feed, mussels also ingest contaminants into their sensitive bodies. Since they burrow at the intersection of water and earth, they suffer with disruptions to both creek channel and water. Their life cycle requires fish to host their parasitic larvae, linking mussels to vulnerable fish diversity. In these ways, mussels embody the whole river.
These mussels have been called naiads, after Greek mythology’s freshwater nymphs – beautiful and powerful, ancient and ageless, epic and endemic – each linked inextricably to a particular stream or river. Naiads give life and draw life from the water. If a river is destroyed, so is its naiad. When a waterway changes, mussels are the first to know. They may simply die, or they may live but be unable to lure fish to their offspring. If their reproduction is thwarted for too long, they go extinct. Aquatic ecologists who study freshwater mussels have been sounding alarms for decades. As eminent biologist and Alabama native E. O. Wilson insists in his foreword to Freshwater Mussels of Alabama and the Mobile Basin, “Mussels are not dismissible, even by those who have little interest in the natural world.”
Mussels’ peril is our own. We need the same thing – plentiful clean water in healthy creeks and rivers. I think of mussels as I watch the kitchen spigot run. I heed their dwindlings and extinctions as a smoke detector piercing the night. Feel alarmed, they insist. Get up and look around. The house just might be on fire.
Tell almost anyone that you’re working with freshwater mussels, and they will leap to culinary conclusions. Whether at a family reunion, a bar, or a boat ramp, people will picture your unionids as the distantly related marine mussels appearing in delicious sauces. They will furrow their brow or wrinkle their nose or grin expectantly and ask the question posed to all mussel biologists: “Can you eat ’em?”
It’s a valid question, worth investigating. When Kentucky-based mussel biologist Wendell Haag was writing North American Freshwater Mussels – an excellent science and history read that deeply explores everything about these mussels – he decided that his research was incomplete. He had never actually eaten a freshwater mussel.
Determined to truly understand these old friends, Haag – accompanied by his intrepid wife and a coworker – eventually tasted them. They cooked up a sampling of freshwater mussels, including Asian clams, species of Quadrula, species of Lampsilis, and Obliquaria reflexa – the three-horned wartyback. They fried some. They boiled some. They roasted some. They made some cocktail sauce to lubricate the eating process but otherwise adhered to their goal of assessing the mussels’ flavor and ate them unadorned.
Haag noted that the smaller mussels, including the Asian clams, were actually quite tender but almost completely lacked flavor. Feeling adventuresome, the wartyback-eating Haags tried some more hefty unionid mussels, which were a different story. “They were very tough and had an odd and disagreeable taste,” Haag reported in his book, adding, “maybe this was the putrescine.” (Freshwater mussels are said to contain a disproportionate amount of putrescine, a chemical characteristic of decaying animal tissue.) Overall, Haag concluded, mussels taste like they smell – peculiar and pungent. While the taste testers didn’t actually become ill from eating the mussels, Haag noted, “the unpleasant memory of the flavor stayed with me for several days.”
Wendell Haag and Andrew and I belong to a group of newcomers on the freshwater mussel scene. Long before anyone donned wet suits to study mussels, humans in North America consumed mussels as a supplementary food source and used their shells as early as ten thousand years ago. Excavated piles of discarded shells, called middens, contain large mussel shells, some fashioned into hoes and scrapers. In the Choctaw Nation – now in Oklahoma – artists carved some shells into spoons or finely made jewelry. Another practice involved burning mussel shells and then crushing them into tiny flakes that, when incorporated into clay, strengthened the Choctaws’ pottery.
These often-massive middens, however, mostly hold smaller, uncarved mussel shells, discarded after people ate the animal inside. Haag suspects that Native people avoided eating larger, tougher mussels and may have had ways of preparing mussels that improved their flavor and digestibility. “I’ll bet you could eat them fine if you got used to them,” he told me. “Especially if you were hungry.” Another possibility – given the decline of water quality and mussels’ embodiment of that water – is that mussels simply used to taste better. Native people’s use of freshwater mussels – for food or tools or art – speaks of an intimacy with creeks and rivers. A perception of subtleties and knowledge of the creek bottom must accompany a reliance on mussels for their meat or shells, especially when harvesting in moderation to preserve a steady supply.
Lacking sufficient hunger or Haag’s gastric courage, however, I have never cooked or tasted freshwater mussels. Eventually, I regretted missing that opportunity. Just months after we ultimately left the South and its wealth of mussels, I discussed eating mussels with newly five-year-old Sam – my first child who visited Chewacla Creek in utero – over a bowl of clam chowder. “I always kind of wanted to try eating mussels,” I said. “I’ll bet we could make some good mussel chowder.”
“No. We couldn’t do that,” Sam said, eyes round.
“Because mussels are part of the Earth!”
“And to make mussel chowder, you’d have to kill them,” he added, scandalized, despite his status as an informed omnivore who delights when he has pig or deer on his plate. He leaned toward me, “You wouldn’t want to kill your favorite animals, would you?”
My favorite animals, being soft bodied, can’t live without their most salient features – hard shells – and their shells, unlike their meat, have continued to attract humans throughout recent history. Mussels build their shells around themselves like snails. A mussel secretes its shell from the thin tissue called a mantle, wrapped like a cloak around the organs. As mussels mature, calcium carbonate joins a material called chitin – the tough yet flimsy stuff of insects’ exterior skeletons – to form a harder composite material.
A mussel grows at the outer edge, laying down curved rings of shell to slowly expand from lentil size to mature mussel size, which can range from the size of your thumb to the size of your face. Mussels grow their shells in layers, adding regular growth rings. Remarkably, they can live for decades, with a few species reaching one hundred years old or more. Cross sections of a shell reveal close estimates of a mussel’s age, although recent evidence suggests that mussels might not create a growth ring every year. If this is true, counting rings could underestimate mussel age, meaning that some mussels might be hundreds of years old.
Mussels sketch a history into the most durable part of themselves. The rings etch into the outermost layer of the mussels’ three-layer shells, which is most often black or brown, sometimes with earthy yellow, green, or reddish colors. We can read clues about the years encoded into these shells, decades of river stories recorded in calcium carbonate. Wendell Haag, among others, has studied these growth rings, carefully cross dating by comparing one mussel’s rings to other mussels' in the same and other rivers. His findings suggest that mussels’ rings respond to large environmental influences, especially stream flow. Like the rings of tree trunks, turtle shells, and fish ear bones, mussel shells are a map of time. Through time, their shells have also been mussels’ downfall, drawing the attention of humans, whose infatuations with these shells killed many mussels.
Hiding inside a mussel’s record of the past, the shell’s most startling layer – the nacre – coats the shell interior. Nacre is the stuff of pearls. Luminous and delicately hued, it ranges from white to pale pink to barely lavender to deep purple. The nacre makes you want to invert the shell to display the mussel’s inner splendor, but because opening them wide kills them, we can only admire the nacre of dead mussels.
Like certain oysters, freshwater mussels can make pearls. Their mantle exudes extra nacre to surround a speck of irritating foreign material, including certain parasites, just inside their shell. Freshwater mussel pearls are typically small and oddly shaped, lacking value. It is rare to find a large or uniform pearl in mussels, such as the one that triggered a pearl rush when a carpenter in New Jersey stumbled upon a ninety-three-grain pearl in 1857. The rarity of this find only enhanced its value and fueled pearl hunters’ imaginations. Over the next 40 years, crowds flocked to creeks and rivers, swarming on banks and sandbars to snatch up bivalved treasure chests.
Then-abundant mussel populations, which flourished in the still-healthy streams, shrank under the onslaught of pearl prospectors, who chased glimmering illusions of fast money. When a stream’s mussel supply faded, the rush shifted elsewhere, spreading from the Northeast to places like Arkansas, Wisconsin, Tennessee, Louisiana, and Texas. By 1900, the pearl fishery folded, but a new mussel craze had taken hold.
As pearl hunters were following reports of mussel populations across the country, they typically pried open a mussel, looked for pearls, and then tossed aside the seemingly worthless shell. In the 1890s, however, those shells got a new reputation. During a snapshot of time, created by a 75-year blaze of industry, freshwater mussel shells appeared on clothing. More precisely, pearly circles of polished nacre served as buttons, holding almost everyone’s clothes together. The mussels whose shell bits fastened so many garments once lived in the Mississippi River, the Alabama River, and elsewhere, harvested by the thousands for their shells.
Habitat destruction is a daunting hurdle for recovering mussel populations.
In factories, circular saws punched pearl buttons from mussel shells. Muscatine, Iowa, a small town whose main streets hug a wide curve of the Mississippi River, became the heart of the button industry. At its peak, this impressive industry relied heavily on large mussel beds in rivers of at least 22 states, throughout the Midwest and into the Southeast. Thousands of people found work harvesting mussels for buttons. These shellers often lived in riverside or houseboat communities and could sell mussels as fast as they could harvest them. They collected mussels with long tongs and rakes. They also snagged mussels by taking advantage of the mussels’ reflexive closure when something poked into their slightly open shell. Several setups worked in similar ways. The crowfoot involved a bar with ropes that held hooks to snag the mussels. Brail boats employed brails – poles or boards that dangled short chains ending in hooks tipped with small beads. The boat dragged the brail along the bottom, and mussels clamped onto the beads. Other mussel hunters dove to the bottom, with or without a surface-air supply line.
In those days of abundant mussels and little regard for preserving habitat or sustainable populations, capturing mussels seemed to require less subtlety and aperture identification than our searches today. Collecting large numbers of mussels from big rivers with no intention of nesting them back into place clearly expedited the process. Mussel harvest for pearl buttons peaked in 1916 but continued into the 1940s, significantly depleting many native mussel populations in large rivers. Some mussel species have since rebounded, after harvesting pressure stopped, just as some populations of crocodiles recovered from depletion after hunting for their skins decreased. In most places, mussel harvest missed just enough individuals to later reestablish a mussel bed. For both mussels and crocodiles, however, habitat destruction became a daunting hurdle for recovering populations.
The pearl button industry was eventually struck down by overexploitation of mussel shells, the invention and mass production of plastic buttons, and the increasing popularity of zippers.
Freshwater mussel harvesting has mostly become a thing of the past. But we seem to be good at wrecking mussels’ lives in other ways, which can more profoundly and enduringly decimate their populations. We destroy the foundations of their homes, poison their water, clog their gill leaflets with particles, render them infertile by removing their host fish, or simply kill them wholesale by drying up the water bodies they live in. Scientists, however, urge us to protect mussels, now finding that we can reap the benefits of mussels by increasing, not decreasing, their numbers and diversity in rivers. As we learn about river health and its relevance to our tenuous water supply, native freshwater mussels emerge as valuable for reasons that do not require us to destroy them.
Adapted from Immersion by writer and veterinarian Abbie Gascho Landis. Reproduced by permission of Island Press, Washington, DC.