Citizen Mussels

North America's freshwater mussels are facing a mass extinction crisis, and ecologists are jumping into rivers to figure out why.

| October 2019

mussel-survey

We’re knee deep in the Farmington River, the four of us, about two miles north of Otis, Massachusetts and somewhere south of Jacob’s Pillow. Ayla Skorupa, the one who called us here, is leaning on a protruding rock in a faded teal wetsuit, my mesh bag of freshwater mussels open at her side. A PhD student at the University of Massachusetts Amherst and researcher with the state’s Cooperative Fish and Wildlife Research Unit, Skorupa puzzles out the species of each mussel, one at a time, notching her fingers along its prominently curved umbo, then drops the most common species, the eastern elliptio, back into the water. The sun’s hot overhead, another 90-degree day in September. The water that pools in my orange sneakers—my lawn-mowing shoes—is startlingly cold.

Behind her, Tim Warren, a colleague with the US Fish and Wildlife Service, is doing the same with the other volunteer’s bag, only faster. He flicks the elliptio a bit further down the mesohabitat we’ve just spent the last thirty minutes crawling up, face down, in four methodical, meter-wide lanes, collecting every mussel we could find. Bag emptied, Skorupa turns and reports my count: “Forty nine elliptio, a triangle, and two creepers.” Then, in response to my hopeful query, she responds with an apologetic shake of the head: “Nope. Zero brook floaters.”

A wayward ellipitio glances off her shoulder and drops into the water. “Hey!” she calls out as Warren mumbles an apology amidst his count. Snorkel in hand, Skorupa eyes up the next 20m stretch while deadpanning a clickbait headline: “Mussel biologist gets knocked out by a mussel.”



There will be no such news story. Media coverage in this line of work is something of a rarity. But word is spreading. Freshwater mussels (Unionoida) are undergoing a mass extinction crisis that has accelerated in the past twenty years. One 2014 study found that “Freshwater mussels have the highest extinction and imperilment rate of any group of organisms on the planet,” with 65% of species currently extinct, endangered, threatened, or vulnerable.

The loss is no small matter. North America is home to the richest diversity of freshwater mussels, with over 300 kinds and counting. Wedged into riverbeds with shells agape and tiny cilia hairs quivering in the current, freshwater mussels can filter up to eight gallons of water per day, depending on the species. They draw out algae and bacteria, along with particulates, including pharmaceuticals and heavy metals, from the water column. Their calcified shells serve as substrate habitat for other fish and river life, and they function as a key food source within an interdependent riverine web.

The origins of the crisis are as old as colonial America’s Industrial Revolution. Freshwater mussel stocks declined in the 19th and 20th centuries as a result of brazen, point-source river pollution and large-scale disruptions from dam and reservoir and channelization projects. River beds were also dragged extensively to harvest mussels for the booming button and cultured pearl market. Even so, and through it all, freshwater mussels seemed to hang on with a determined, hard-shelled resilience. Like a rock.

But this latest precipitous decline in mussel abundances is deeply worrying since the remaining mussel beds are more fragmented than ever. Their method of reproduction, too, relies on a complex, parasitic relationship with certain host fish. Most female mussels, when gravid with fertilized glochidia, will dangle a fleshy bait that explodes thousands of hitchhiking larva into the gills of a duped fish. After a few months parasitizing on fish blood, the juvenile mussels cast off for a new spot in the riverbed. While the odds have always been stark—tens of thousands of initial glochidia resulting in a few hundred juvenile mussels—they were still high enough.

Now, in these first decades of the 21st century, something is decidedly off: researchers speculate that it might be water temperature changes in streams and reservoirs or pesticides impacting the glochidia or alterations in fish migration patterns. What they do know is that older mussels are reaching the end of their lives, which can be somewhere between a decade or two for most species and, astoundingly, over two hundred years, in the case of the freshwater pearl mussel. Meanwhile, freshwater mussel progeny are collectively in very short supply.

The extinction crisis is generating a quick shift in research attention with growing cooperation across national and state agencies, local conservation authorities, and aquatic scientists. And habitat surveys, like this slow crawl up 100meters of the Farmington, are part of that wider scientific effort to crowd-source some of the information-gathering. In early summer, Skorupa had posted a call in the Connecticut River Conservancy newsletter asking for volunteers willing to wade into rivers and count mussels. On a whim, I signed up.

Skorupa likens freshwater mussel surveying to a hunt for buried treasure. She caught the mussel bug, as she calls it, several years ago as an intern at MassWildlife with Dr. Peter Hazelton. Now she’s conducting diet studies, augmentation efforts, and habitat research on the evasive brook floater, which is currently under federal review for national protection and is dangling from the edge of the state’s endangered list by its bright cantaloupe-colored foot.

mussel-survey

Granted, I didn’t know any of this when I first volunteered. But after two habitat surveys, I seem to have caught the mussel bug as well. A few months later, I asked if I could visit the research lab where Skorupa is working to propagate brook floaters. In mid-November after the first snowfall of the season, I pulled up to the Richard Cronin Aquatic Resources Center, a resuscitated 1980s salmon hatchery that looks out across a sweep of the Connecticut River and the sheer cliff of Sugarloaf Mountain. Clad in a thick fleece sweater, Skorupa showed me around a trio of tanks holding rainbow, brown, and brook trout and in which she is prepping to introduce brook floater glochidia strands. While some mussels are notoriously picky about their particular host fish (one stalwart malacologist with the Minnesota Department of Natural Resources painstakingly tried to pair 70 different species with the spectaclecase mussel until he landed, propitiously and finally, on a singular, migratory fish), brook floaters are, happily, “host generalists”—they’re willing to “parasitize” just about any gills. Skorupa is eager to find out which easily-sourced trout species works best in lab conditions.

Retreating to a warmer office lab where Lucinda Williams played from an open laptop, Skorupa pointed to several aquarium tanks that bubbled behind a sectional wall. They held the several hundred juvenile floaters she has successfully propagated, in vivo, thus far. I could just make them out embedded in a layer of river sand on the glass-bottomed tanks. They ranged from the size of tiny stones to the size of my pinky fingernail. The oldest are now eighteen months old, and Skorupa is hoping to release her first 150 Brook Floaters in several controlled studies come spring, once the permits are in order and her mussels are declared free of any known fish diseases.



Freshwater mussel research is complex and interdependent, and I found myself returning to a question I had on my first habitat survey: what’s a freshwater mussel worth? I wondered aloud whether scientists had managed to quantify, say, the filtration services that a single mussel offers our river systems. The Millennium Ecosystem Assessment has pioneered these kinds of appraisal efforts, which link ecosystem services to human well-being—the goal being to improve the way decisions are weighed and made in how ecosystems are managed. Skorupa turned the question over to Dave Perkins, the director of the center and a US Fish & Wildlife Service biologist. He noted that while the full ecosystem services of an individual mussel are hard to quantify, there are existing formulas that assign costs at the permitting stage to large-scale projects that will impact a river system. Some of the funding for the various research work here at Cronin comes from this kind of remediation money, as well as through the Massachusetts Endangered Species Program, and from the Massachusetts Environmental Trust’s specialty license plate program.

But Dr. Allison Roy urged caution on my line of questioning a few days later when I visit her third floor office in the Department of Environmental Conservation at UMass Amherst. An aquatic biologist with the US Geological Survey, Roy is one of the principle investigators on the brook floater project. The wooden laminate desk between us is entirely clear, with a computer and stacks of blue foldered papers cornered behind her. She says she understands the societal impulse to “put a number on freshwater mussels” and it’s certainly helpful in assessing mitigation costs. Even so, she argues, it’s a risky way of thinking, especially if we imagine freshwater mussels as solely water filtration units. She points out that the zebra mussel is an aggressively invasive species that brought clearer waters to the Great Lakes waterways but at extensive costs to a diverse, native ecosystem.

Roy, it is clear, relishes the complexities of environmental science research. She grows more animated as she talks, leaning across the desk and weighing the paradoxes in either hand. She’s wrapping up a course on dam removal, for example, and highlights for me the complications that arise from re-disrupting rivers or draining down reservoirs. Some mussel species on the brink of extinction are currently benefiting from the controlled flow and algae in the tailwaters of existing dams. Freshwater mussels, in other words, should not be considered separate from their multiple roles in a dynamic ecosystem. There must be humility in the endeavor.

Back on the Farmington River, I watch as the others around me glide forward on their stomachs, effortlessly breathing through their mouthpieces. I’m a novice snorkeler, so I wait for the others to start lest they see me thrashing about for a heart-pounding minute while I gulp plastic oxygen and slowly quell my body’s innate defense mechanisms. Then, I blink my way into this alternate, alluvial world. Small bug-eyed crayfish step forward to investigate. Juvenile trout swim alongside as I move my arms through rods of sheering sunlight. Occasional trucks barrel their way over the Highway 8 bridge upstream. River prone, I scan the red bottom for tell-tale bubbles, pulling my weightless way toward fleshy gills that open strange-haired clefts in the sand.

I’m learning about the very existence of freshwater mussels just as they are at risk of disappearing. It reminds me of Mary Oliver’s comment in Long Life, that “the beauty and strangeness of the world” offers a simultaneity of refreshment and terror: “on the one side is radiance,” she writes, “on another is the abyss.” Over in Skorupa’s lane I hear a cheer warble up from her mouthpiece. As it turns out, she’s found a brook floater, a bit of buried treasure and one of two we find that day. On this edge of existence, it strikes me, the radiance is as thin, as splayed with color, and as strong as a freshwater mussel’s calcite shell.


GEOFF MARTIN’s recent place-based and environmental writing has appeared or is forthcoming in Boulevard, Slag Glass City, The Drum, and The Common. Find him at www.geoff-martin.com or on Twitter @gmartin9

Reprinted from Boulevard (Spring 2019).




Facebook Instagram Twitter

click me