Ecosystems

Scientists have teamed up with tiger sharks to uncover the largest expanse of seagrasses on Earth.  

A massive survey of the Bahamas Banks — a cluster of underwater plateaus surrounding the Bahama archipelago — reveals 92,000 square kilometers of seagrasses, marine biologist Oliver Shipley and colleagues report November 1 in Nature Communications. That area is roughly equivalent to half the size of Florida.

The finding expands the estimated global area covered by seagrasses by 41 percent — a potential boon for Earth’s climate, says Shipley, of the Herndon, Va.–based ocean conservation nonprofit Beneath The Waves.

Austin Gallagher, a marine biologist from ocean conservation nonprofit Beneath The Waves, surveys a seagrass field in the Bahamas Banks.Cristina Mittermeier and SeaLegacy

Seagrasses can sequester carbon for millennia at rates 35 times faster than tropical rainforests. The newly mapped sea prairie may store 630 million metric tons of carbon, or about a quarter of the carbon trapped by seagrasses worldwide, the team estimates.

Mapping that much seagrass was a colossal task, Shipley says. Guided by previous satellite observations, he and colleagues dove into the sparkling blue waters 2,542 times to survey the meadows up close. The team also recruited eight tiger sharks to aid their efforts. Similar to lions that stalk zebra through tall grasses on the African savanna, the sharks patrol fields of wavy seagrasses for grazing animals to eat (SN: 1/29/18; SN: 5/21/19, SN: 2/16/17).

“We wouldn’t have been able to map anywhere near the extent that we mapped without the help of tiger sharks,” Shipley says.

The team captured the sharks with drumlines and hauled each one onto a boat, mounting a camera and tracking device onto the animal’s back before releasing it. The sharks were typically back in the water in under 10 minutes. The team operated like “a NASCAR pit crew,” Shipley says.

Researchers had previously suggested tracking seagrass-grazing sea turtles and manatees to locate pastures. But tiger sharks were a smart choice because they roam farther and deeper, says Marjolijn Christianen, a marine ecologist at Wageningen University & Research in the Netherlands who was not involved in the new work. “That’s an advantage.”

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Camera-equipped tiger sharks like this one helped uncover the world’s largest seagrass bed, penetrating areas too deep or remote for divers.

Shipley and colleagues plan to collaborate with other animals — including ocean sunfish — to uncover more submarine meadows (SN: 5/1/15). “With this [approach], the world’s our oyster,” he says. More

Fen, Bog & SwampAnnie ProulxSimon & Schuster, $26.99

A recent TV ad features three guys lost in the woods, debating whether they should’ve taken a turn at a pond, which one guy argues is a marsh. “Let’s not pretend you know what a marsh is,” the other snaps. “Could be a bog,” offers the third.

It’s an exchange that probably wouldn’t surprise novelist Annie Proulx. While the various types of peatlands — wetlands rich in partially decayed material called peat — do blend together, I can’t help but think, after reading her latest book, that a historical distaste and underappreciation of wetlands in Western society has led to the average person’s confusion over basic peatland vocabulary.

In Fen, Bog & Swamp: A Short History of Peatland Destruction and Its Role in the Climate Crisis, Proulx seeks to fill the gaps. She details three types of peatland: fens, which are fed by streams and rivers; bogs, fed by rainwater; and swamps, distinguishable by their trees and shrubs. While all three ecosystems are found around most of the world, Proulx focuses primarily on northwestern Europe and North America, where the last few centuries of modern agriculture led to a huge demand for dry land. Wet, muddy and smelly, wetlands were a nightmare for farmers and would-be developers. Since the 1600s, U.S. settlers have drained more than half of the country’s wetlands; just 1 percent of British fens remains today.

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Only recently have the consequences of these losses become clear. “We are now in the embarrassing position of having to relearn the importance of these strange places,” Proulx writes. For one, peatlands have great ecological value, supporting a variety of wildlife. They also sequester huge amounts of carbon dioxide, and some peatlands prevent shoreline erosion, while buffering land from storm surges (SN: 3/17/18, p. 20). But the book doesn’t spend too much time on nitty-gritty ecology. Instead, Proulx investigates these environments in the context of their relationship with people.

Known for her fiction, Proulx, who penned The Shipping News and “Brokeback Mountain,” draws on historical accounts, literature and archaeological digs to imagine places lost to time. She challenges the notion that wetlands are purely unpleasant or disturbing — think Shrek’s swamp, where only an ogre would want to live, or the Swamps of Sadness in The Neverending Story that swallow up Atreyu’s horse.

Proulx jumps back as far as 20,000 years ago to the bottom of the North Sea, which at the time was a hilly swath called Doggerland. When sea levels rose in the seventh century B.C., people there learned to thrive on the region’s developing fens, hunting for fish and eels. In Ireland, “bog bodies” — many thought to be human sacrifices — have been preserved in the peat for thousands of years; Proulx imagines torchlit ceremonies where people were offered to the mud, a connection to the natural world that is hard for many people to comprehend today. These spaces were integrated into the local cultures, from Renaissance paintings of wetlands to British lingo such as didder (the way a bog quivers when stepped on). Proulx also reflects on her own childhood memories — wandering through wetlands in Connecticut, a swamp in Vermont — and describes how she, like writer Henry David Thoreau, finds beauty in these places. “It is … possible to love a swamp,” she says.

Fens, bogs and swamps are technically distinct, but they’re also fluid; one wetland may transition into another depending on its water source. This same fluidity is reflected in the book, where Proulx flits from one wetland to another, from one part of the world to another, from one millennium to another. At times didactic and meandering, Proulx will veer off to discuss humankind’s destructive tendency not just in wetlands, but nature in general, broadly rehashing aspects of the climate crisis that most readers interested in the environment are probably already familiar with. I was most enthralled — and heartbroken — by the stories I had never heard before: of “Yde Girl,” a redheaded teenager sacrificed to a bog; the zombie fires in Arctic peatlands that burn underground; and the ivory-billed woodpecker, a bird missing from southern U.S. swamps for almost a century.

Buy Fen, Bog & Swamp from Bookshop.org. Science News is a Bookshop.org affiliate and will earn a commission on purchases made from links in this article. More

The undoing of toxic “forever chemicals” may be found in products in your pantry.

Perfluoroalkyl and polyfluoroalkyl substances, also known as PFAS, can persist in the environment for centuries. While the health impacts of only a fraction of the thousands of different types of PFAS have been studied, research has linked exposure to high levels of some of these widespread, humanmade chemicals to health issues such as cancer and reproductive problems.

Now, a study shows that the combination of ultraviolet light and a couple of common chemicals can break down nearly all the PFAS in a concentrated solution in just hours. The process involves blasting UV radiation at a solution containing PFAS and iodide, which is often added to table salt, and sulfite, a common food preservative, researchers report in the March 15 Environmental Science & Technology.

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“They show that when [iodide and sulfite] are combined, the system becomes a lot more efficient,” says Garrett McKay, an environmental chemist at Texas A&M University in College Station who was not involved in the study. “It’s a big step forward.”

A PFAS molecule contains a chain of carbon atoms that are bonded to fluorine atoms. The carbon-fluorine bond is one the strongest known chemical bonds. This sticky bond makes PFAS useful for many applications, such as water- and oil-repellant coatings, firefighting foams and cosmetics (SN: 6/4/19; SN: 6/15/21). Owing to their widespread use and longevity, PFAS have been detected in soils, food and even drinking water. The U.S. Environmental Protection Agency sets healthy advisory levels for PFOA and PFOS — two common types of PFAS — at 70 parts per trillion.

Treatment facilities can filter PFAS out of water using technologies such as activated carbon filters or ion exchange resins. But these removal processes concentrate PFAS into a waste that requires a lot of energy and resources to destroy, says study coauthor Jinyong Liu, an environmental chemist at the University of California, Riverside. “If we don’t [destroy this waste], there will be secondary contamination concerns.”

One of the most well-studied ways to degrade PFAS involves mixing them into a solution with sulfite and then blasting the mixture with UV rays. The radiation rips electrons from the sulfite, which then move around, snipping the stubborn carbon-fluorine bonds and thereby breaking down the molecules.

But some PFAS, such as a type known as PFBS, have proven difficult to degrade this way. Liu and his colleagues irradiated a solution containing PFBS and sulfite for an entire day, only to find that less than half of the pollutant in the solution had broken down. Achieving higher levels of degradation required more time and additional sulfite to be poured in at spaced intervals.

The researchers knew that iodide exposed to UV radiation produces more bond-cutting electrons than sulfite. And previous research has demonstrated that UV irradiation paired with iodide alone could be used to degrade PFAS chemicals.

So Liu and his colleagues blasted UV rays at a solution containing PFBS, iodide and sulfite. To the researchers’ surprise, after 24 hours of irradiation, less than 1 percent of the stubborn PFBS remained.

What’s more, the researchers showed that the process destroyed other types of PFAS with similar efficiency and was also effective when PFAS concentrations were 10 times that which UV light and sulfite alone could degrade. And by adding iodide the researchers found that they could speed up the reaction, Liu says, making the process that much more energy efficient.

In the solution, iodide and sulfite worked together to sustain the destruction of PFAS molecules, Liu explains. When UV rays release an electron from iodide, that iodide is converted into a reactive molecule which may then recapture freed electrons. But here sulfite can step in and bond with these reactive molecules and with electron-scavenging oxygen in the solution. This sulfite “trap” helps keep the released electrons free to cut apart PFAS molecules for eight times longer than if sulfite wasn’t there, the researchers report.

It’s surprising that no one had demonstrated the effectiveness of using sulfite with iodide to degrade PFAS before, McKay says.

Liu and his colleagues are now collaborating with an engineering company, using their new process to treat PFAS in a concentrated waste stream. The pilot test will conclude in about two years. More

In the unceasing battle against dust, humans possess a deep arsenal of weaponry, from microfiber cloths to feather dusters to vacuum cleaners. But new research suggests that none of that technology can compare to nature’s secret weapon — biological soil crusts.

These biocrusts are thin, cohesive layers of soil, glued together by dirt-dwelling organisms, that often carpet arid landscapes. Though innocuous, researchers now estimate that these rough soil skins prevent around 700 teragrams (30,000 times the mass of the Statue of Liberty) of dust from wafting into the air each year, reducing global dust emissions by a staggering 60 percent. Unless steps are taken to preserve and restore biocrusts, which are threatened by climate change and shifts in land use, the future will be much dustier, ecologist Bettina Weber and colleagues report online May 16 in Nature Geoscience.

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Dry-land ecosystems, such as savannas, shrublands and deserts, may appear barren, but they’re providing this important natural service that is often overlooked, says Weber, of the Max Planck Institute for Chemistry in Mainz, Germany. These findings “really call for biocrust conservation.”

Biocrusts cover around 12 percent of the planet’s land surface and are most often found in arid regions. They are constructed by communities of fungi, lichens, cyanobacteria and other microorganisms that live in the topmost millimeters of soil and produce adhesive substances that clump soil particles together. In dry-land ecosystems, biocrusts play an important role in concentrating nutrients such as carbon and nitrogen and also help prevent soil erosion (SN: 4/12/22).

And since most of the world’s dust comes from dry lands, biocrusts are important for keeping dust bound to the ground. Fallen dust can carry nutrients that benefit plants, but it can also reduce water and air quality, hasten glacier melting and reduce river flows. For instance in the Upper Colorado River Basin, researchers found that dust not only decreased snow’s ability to reflect sunlight, but it also shortened the duration of snow cover by weeks, reducing flows of meltwater into the Colorado River by 5 percent. That’s more water than the city of Las Vegas draws in a year, says Matthew Bowker, an ecologist from Northern Arizona University in Flagstaff who wasn’t involved in the new study.

Experiments had already demonstrated that biocrusts strengthened soils against erosion, but Weber and her colleagues were curious how that effect played out on a global scale. So they pulled data from experimental studies that measured wind velocities needed to erode dust from various soil types and calculated how differences in biocrust coverage affected dust generation. They found that the wind velocities needed to erode dust from soils completely shielded by biocrusts were on average 4.8 times greater than the wind velocities need to erode bare soils. 

The researchers then incorporated their results, along with data on global biocrust coverage, into a global climate simulation which allowed them to estimate how much dust the world’s biocrusts trapped each year.  

“Nobody has really tried to make that calculation globally before,” says Bowker. “Even if their number is off, it shows us that the real number is probably significant.”

Using projections of future climate conditions and data on the conditions biocrusts can tolerate, Weber and her colleagues estimated that by 2070, climate change and land-use shifts may result in biocrust losses of 25 to 40 percent, which would increase global dust emissions by 5 to 15 percent.

Preserving and restoring biocrusts will be key to mitigating soil erosion and dust production in the future, Bowker says. Hopefully, these results will help to whip up more discussions on the impacts of land-use changes on biocrust health, he says. “We need to have those conversations.” More

As climate change brings more wildfires to the western United States, a rare fungal infection has also been on the rise. Valley fever is up more than sixfold in Arizona and California from 1998 to 2018, according to the U.S. Centers for Disease Control and Prevention.

Valley fever causes coughs, fevers and chest pain and can be deadly. The culprit fungi, members of the genus Coccidioides, thrive in soils in California and the desert Southwest. Firefighters are especially vulnerable to the disease. Wildfires appear to stir up and send the soil-loving fungi into the air, where they can enter people’s lungs.

If the fires are helping these disease-causing fungi to get around, could they be sending other microorganisms aloft as well? Leda Kobziar, a fire ecologist at the University of Idaho in Moscow, decided in 2015 to see if she could find out if and how microorganisms like bacteria and fungi are transported by wildfire smoke — and what that might mean for human and ecological health.

By 2018, Kobziar had launched a new research field she named “pyroaerobiology.” First, she asked if microorganisms can even survive the searing heat of a wildfire. The answer, she found, is yes. But how far bacteria and fungi can travel on the wind and in what numbers are two of the many big unknowns.

With a recent push to spark new collaborations and investigations, Kobziar hopes that scientists will start to understand how important smoke transport of microbes may be.

For Kobziar’s earliest studies in 2015, her students held up petri dishes on long poles to collect samples of the smoky air near a prescribed fire at the University of Florida experimental forest.L. Kobziar

Today, Kobziar and colleagues use drones to collect samples at the University of Florida experimental forest.L. Kobziar

Invisible but pervasive

Air may look clear, but even in the cleanest air, “hundreds of different bacteria and fungi are blowing around,” says Noah Fierer, a microbiologist at the University of Colorado Boulder.

Winds whisk bacteria and fungi off all kinds of surfaces — farm fields, deserts, lakes, oceans. Those microbes can rise into the atmosphere to travel the world. Scientists have found microorganisms from the Sahara in the Caribbean, for example.

Many (if not most) of the airborne microorganisms, including bacteria, fungi and viruses, are not likely to cause disease, Fierer notes. But some can make people sick or cause allergic reactions, he says. Others cause diseases in crops and other plants.

The billions of tons of dust that blow off of deserts and agricultural fields each year act as a microbial conveyor belt. In places like Arizona, people know to be alert for symptoms of airborne illnesses like Valley fever after dust storms, since infections increase downwind afterward. If dust can move living microorganisms around the globe, it makes sense that particulates in smoke would be microbe movers too, Kobziar says — assuming the microscopic life-forms can survive a fire and a spin in the atmosphere.

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Tiny travelers

Rising temperatures and worsening droughts have led to longer and more intense wildfire seasons across the West (SN: 9/26/20, p. 12). Breathing wildfire smoke makes people sick (SN Online: 9/18/20), even causing premature death from heart and lung illnesses. In the United States, wildfire smoke causes about 17,000 premature deaths per year — a number projected to double by 2100, according to a 2018 study in GeoHealth.

In other parts of the world, the effects are far worse. In 2015, smoke from illegal land-clearing blazes plus wildfires in Indonesia killed an estimated 100,000 people across Southeast Asia, according to a 2016 report in Environmental Research Letters. Blame is usually attributed to particulate matter — organic and inorganic particles suspended in the air, including pollen, ash and pollutants. But scientists and health officials are increasingly realizing that there’s an awful lot we don’t know about what else in smoke is affecting human health.

The most intense fires, the ones that burn the hottest and release the most energy, can create their own weather systems and send smoke all the way into the stratosphere, which extends about 50 kilometers above Earth’s surface (SN: 9/14/19, p. 12). Once there, smoke can travel around the world just as ash from explosive volcanoes does. Kobziar’s team and others provided compelling evidence in the February ISME Journal that live, viable microorganisms can be carried in smoke plumes — at least near Earth’s surface if not higher up.

The Fire and Smoke Model Evaluation Experiment, or FASMEE, team set this high-intensity crown fire in the aspens of Fishlake National Forest, Utah, in 2019. The team used a drone to measure microbial concentrations in this smoke.L. Kobziar

In 2015, while at the University of Florida in Gainesville, Kobziar and her students collected the first air samples for this line of research during a series of planned, or prescribed, burns that Kobziar set at the school’s experimental forest. The group arrived at the forest armed with 3-meter-long poles topped with petri dishes to collect samples from the air.

Before any fires were set, the team held the petri dishes in the air for three minutes to collect air samples as a pre-fire baseline. Then Kobziar, a certified prescribed burn manager (or as she calls it, a “fire lighter”), lit the fires. Once flames were spreading at a steady rate and smoke was billowing, students hoisted new petri dishes into the smoke, almost as if aiming a marshmallow on a stick at a campfire. This allowed them to collect smoky air samples to compare to the “before” samples.

Back in the lab, in a dark room held at a constant 23° Celsius, both the baseline and smoky petri dishes — covered and sealed from further contamination — were left for three days. Microbes began to grow. Far more bacterial and fungal species populated the smoky petri dishes than the baseline dishes, indicating that the fire aerosolized some species that weren’t in the air before the fire, Kobziar says.

These petri dishes show bacterial and fungal colonies that grew after five minutes of exposure to smoke. The smoke came from pine needles collected from Florida then burned in Kobziar’s University of Idaho lab.L. Kobziar

These petri dishes show bacterial and fungal colonies that grew after five minutes of exposure to smoke. The smoke came from pine needles collected from Florida then burned in Kobziar’s University of Idaho lab.L. Kobziar

“We were stunned at how many different microbial colonies survived the combustion environment and grew in the smoke samples, compared to very few in the ambient air,” she says. Based on DNA tests, Kobziar’s team identified 10 types of bacteria and fungi; some are pathogenic to plants, one is an ant parasite and one helps plants absorb nutrients. “This was the moment when the way we thought about smoke was completely transformed,” she says.

In 2017, after Kobziar had moved to Idaho, her team collected soil samples from the University of Idaho’s experimental forest and burned them — this time, in the lab. As smoke unfurled above the burning soils, the researchers collected air samples, and again, sealed them and put them in a dark, warm room to see what would grow. After a week, lots of different microbes, including fungi, had multiplied into colonies on the plates, the researchers reported in 2018 in Ecosphere.

Alive and on the move

Since then, Kobziar’s team has collected more air samples during prescribed burns of varying intensities in Florida, Idaho, Montana and Utah, joining forces with the U.S. Forest Service Fire and Smoke Model Evaluation Experiment, or FASMEE, team. For her students’ safety, she’s replaced the poles and petri dishes with drones. She sends a single drone carrying a vacuum pump with a filter into smoke plumes at varying altitudes up to 120 meters, the team described in the journal Fire in 2019.

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The FASMEE team set up a mobile research lab on the fire line at Fishlake National Forest. Drone operators sent the machines into the smoke to collect samples, back to the “lab” to return samples, then back up to collect more multiple times. They found about 1,000 different microbe types in the smoke.

In every experiment, the researchers have found living bacteria and fungi, many of which were not found in any of the air samples taken before the fires. In Utah smoke samples, for example, the FASMEE team found more than 100 different fungi that were not in the air before the fire, Kobziar says. Findings included species of Aspergillus, which can cause fevers, coughs and chest pain, as well as Cladosporium, molds that can cause allergies and asthma.

Whether any of these microorganisms pose a danger to people is unknown, Kobziar cautions. Her team has not tested whether the microbial species that survive the heat can cause disease, but the group plans to do so.

The research in Utah revealed another crucial fact: These microbes are tough. Even in smoke from high-intensity, high-temperature fires, about 60 percent of bacterial and fungal cells are alive, Kobziar says. Roughly 80 percent seem to survive lower-intensity fires, which is “about the same percentage of cells we’d expect to see alive in ambient air conditions,” she says. Thus, these first studies show that fires are sending live bacteria and fungi into the air. And that they can travel at least 120 meters above the ground and close to a kilometer from a flame front.

But many basic questions remain, Kobziar says. How do the microbes change — in quantity, type or viability — based on distance traveled away from the flames? How far can they actually go? How do different fuel sources — pine trees, grasslands, deciduous trees or crops, for example — affect microbial release? How does fire intensity affect what is released and how far it travels? Does the type of combustion — smoldering (like a wet log on a campfire) versus high-intensity flaming fires — affect what is released? How does temperature or humidity or weather affect microbial survival?

Then, of course, Kobziar has plenty of questions about how to conduct this new field of research: What are the safest and best ways to sample the air in the dangerous environment of an unpredictable wildfire? How do you avoid contaminating the biological samples?

She’s been learning as she goes, honing her methodology. The answers to many of those questions could come if one of Kobziar’s dream collaborations comes true: She wants to work with the researchers whose studies involve the NASA DC-8 “flying laboratory,” which explores Earth’s surface and atmosphere for studies ranging from archaeology to volcanology.

Researchers have already tracked many different chemicals released by fires into the stratosphere from the Arctic to the South Pacific and everywhere in between, using the DC-8 for NASA’s Atmospheric Tomography Mission, says Christine Wiedinmyer, a fire emissions modeler at the Cooperative Institute for Research in Environmental Sciences in Boulder, Colo. Finding traceable signatures of fires everywhere in the atmosphere suggests that fires could also be sending bacteria and fungi around the world, she says.

Nine kilometers above Earth’s surface, a camera on NASA’s DC-8 flying laboratory took this image of thunderclouds rising above columns of smoke from a fire in eastern Washington on August 8, 2019. Such storms, formed by intense fires, loft particulate matter, chemicals and maybe even microbes into the stratosphere.David Peterson/U.S. Naval Research Lab

“Pyroaerobiology is so cool,” says Wiedinmyer, who tracks and simulates the movement of chemicals in wildfire smoke around the world. She sees no reason that such atmospheric chemistry models couldn’t also be used for tracking and forecasting the movement of microbes in smoke plumes — once researchers collect sufficient measurements. Those data might answer basic questions about the human health hazards of microorganisms in smoke.

Microbiologist Fierer in Boulder and Wiedinmyer have collaborated on chemistry sampling and modeling. The two plan to move to bacterial and fungal modeling using data Fierer is gathering on microbial concentrations in wildfire smoke.

Kobziar, meanwhile, is working with atmospheric modelers to figure out how to model microbes’ movements in smoke. The long-term aim is to develop models to supplement current air-quality forecasts with warnings of air-quality issues across the United States related to wildfire-released microorganisms in smoke.

A U.S. map

While Kobziar’s team focuses on measuring microbes in smoke, Fierer’s team is working to get a baseline of what microbes are in the air at different locations during normal times and then comparing the baseline to smoke. The group has been sampling indoor and outdoor air at hundreds of U.S. homes to “map out what microbes we’re breathing in as we’re walking around doing our daily business,” Fierer says. They are also sampling air across Colorado, which experienced record-breaking fires in 2020 (SN: 12/19/20 & 1/2/21, p. 32).

Fierer’s team uses sampling stations with small, high-powered vacuums atop 2-meter-high poles to “sample air for a period of time without smoke. Then boom, smoke hits [the site], we sample for a few days when there’s smoke in the air, and then we also sample afterward,” Fierer says. Analyzing samples from before, during and after a fire is ideal, he says, as there’s tremendous variation in microbial and fungal populations in the air. Near a Midwestern city in winter, for example, microorganisms might include ones associated with local trees or, strangely, dog feces; near a Colorado cattle feedlot in summer, microbes might include those associated with cattle feces.

Joanne Emerson, then a postdoctoral researcher at the University of Colorado Boulder, samples air atop a 300-meter-tall tower at the Boulder Atmospheric Observatory.N. Fierer

When the team gets its results — data collection and analysis have been delayed by the pandemic — Fierer says, “we will know the amounts and types of microbes found in wildfire smoke compared with paired smoke-free air samples, and whether those microbes are viable.” At least in Colorado. Once scientists get the measurements of how many microbes can be carried in smoke, and to what altitudes, Fierer’s group can combine that information with global smoke production numbers to come up with “some back-of-the-envelope calculations” of the volume of microbes traveling in smoke plumes. Eventually, he says, scientists could figure out how many are alive, and whether that even matters for human health — still “an outstanding question.”

Big leaps forward could be made if more scientists get involved in the research, Fierer and Kobziar both say. This research needs a truly multidisciplinary approach, with microbiologists, forest ecologists and atmospheric scientists collaborating, Fierer says. Going it alone would “be equivalent to a microbiologist studying microbes in the ocean and not knowing anything about oceanography,” he says. Fortunately, after Kobziar and infectious disease physician George Thompson of the University of California, Davis published a call-to-arms paper in Science last December, summing up their pyroaerobiology research and noting key questions, several researchers from different fields expressed interest in investigating the topic. “That’s exactly what we hoped would happen,” Kobziar says.

Is there danger?

In recent years, Thompson has seen a substantial increase in patients getting Valley fever and other fungal infections after nearby wildfires. He was well aware that when particulate matter in smoke gets into the lungs, it can cause breathing difficulties, pneumonia and even heart attacks. In fact, scientists reported in the Journal of the American Heart Association in April 2020 that exposure to heavy smoke during 2015–2017 wildfires in California raised the risk of heart attacks by up to 70 percent.

He began to wonder if California’s record-breaking infernos were stirring up other microbes along with the fungus that causes Valley fever. So he joined forces with Kobziar.

The Valley fever link appears to be real, but so far, local. For example, after the 2003 Simi Fire burned through Ventura County, more than 70 people got sick with Valley fever. But whether the Coccidioides fungi can travel to make people sick at a distance from the fire, no one knows.

There are ways to figure out if more people, either locally or farther away, are getting sick with bacterial or fungal infections after wildfires. One way, Thompson says, is to look at a community’s antibiotic prescriptions and hospitalizations in the month preceding and the month after a fire: More prescriptions or hospitalizations from bacterial or fungal infections after a fire could indicate a link.

In 2019 at the American Transplant Congress meeting, for example, researchers linked California wildfires with increased hospitalizations related to Aspergillus mold and Coccidioides fungi infections.

But until we know more about what microbes fires release and where they go, we won’t know how important such a link is for human health, Fierer says.

There’s so much we don’t know yet, Thompson agrees. “We still have a lot of work to do. This is sort of the beginning of the beginning of the story.” More

Joshua Smith has been diving in kelp forests in Monterey Bay along the central coast of California since 2012. Back then, he says, things looked very different. Being underwater was like being in a redwood forest, where the kelp was like “towering tall cathedrals,” says Smith, an ecologist at the University of California, Santa Cruz. Their tops were so lush that it was hard to maneuver a boat across them.

No longer. The once expansive kelp forests are now a mosaic of thinner thickets interspersed with barrens colonized by sea urchins. And those sea urchins have so little to eat, they aren’t even worth the effort of hungry sea otters — which usually keep urchins in check and help keep kelp forests healthy, Smith and his colleagues report March 8 in the Proceedings of the National Academy of Sciences.

A similar scene is playing out farther north. A thick kelp forest once stretched 350 kilometers along the northern California coast. More than 95 percent of it has vanished since 2014, satellite imagery shows. Once covering about 210 hectares on average, those forests have been reduced to a mere 10 hectares scattered among a few small patches, Meredith McPherson, a marine biologist also at UC Santa Cruz, and her colleagues report March 5 in Communications Biology. Like the barrens farther south, the remaining forests are now covered by purple sea urchins.

Satellite images in 2008 (left) and 2019 (right) of a section of the northern California coastline reveal a 95 percent reduction in the area covered by underwater kelp forests (yellow).Meredith McPherson

Satellite images in 2008 (left) and 2019 (right) of a section of the northern California coastline reveal a 95 percent reduction in the area covered by underwater kelp forests (yellow).Meredith McPherson

Together, the two studies reveal the devastation of these once resilient ecosystems. But a deeper dive into the cascading effects of this loss may also provide clues to how at least some of these forests can bounce back.

California’s kelp forests, which provide a rich habitat for marine organisms, got hit by a double whammy of ecological disasters in the past decade, says UC Santa Cruz ecologist Mark Carr. He is a coauthor on the Communications Biology paper who has mentored both McPherson and Smith.

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First, sea star wasting syndrome wiped out local populations of sunflower sea stars (Pycnopodia helianthoides), which typically feed on urchins (SN: 1/20/21). Without sea stars, purple sea urchins (Strongylocentrotus purpuratus) proliferated.

The second wallop was a marine heat wave so big and persistent it was nicknamed “The Blob” (SN: 12/14/17). While kelp forests have been resilient to warming events before, this one was so extreme it spiked temperatures in many parts of the Pacific to 2 to 3 degrees Celsius above normal (SN: 1/15/20).

Kelp thrives in cold and nutrient rich water. As its growth slowed in the warmer water, less kelp drifted into the crevices of the reefs where sea urchins typically lurk. With a key predator gone and a newfound need to forage for food rather than waiting for it to come to them, urchins emerged and turned the remaining kelp into a giant buffet.

For the northern California kelp forests, the shift could spell doom for two reasons. The dominant species growing there is bull kelp (Nereocystis leutkeana). It dies each winter to return again in the spring, and the changes are making it more difficult to bounce back year after year.  In comparison, one of the main kelp species in Monterey Bay is giant kelp (Macrocystis pyrifera), which lives for many years, making it a bit more resilient.

Bull kelp (Nereocystis leutkeana), seen here growing at Pescadero Point near Carmel-by-the-Sea, Calif., becomes the dominant species of kelp growing along the northern California coast. A marine heat wave and loss of a sea urchin predator has led to a massive loss of bull kelp in that region.Steve Lonhart/NOAA, MBNMS

The kelp forests in the north also lack an urchin predator common farther south: sea otters. Those sea otters are what’s providing a glimmer of hope in Monterey Bay. Smith and his colleagues wondered how the bonanza of sea urchins was affecting the otters. They found that sea otters were eating three times as many sea urchins as they were before 2014, but they were being picky. They avoided the more populous urchin barrens, instead feasting only on urchins in the remaining patches of kelp. That’s because the barrens offer only a poor diet of scraps, leaving the urchins there essentially hollow on the inside. “Zombies,” Smith calls them.

The nutrient-rich urchins in the healthy kelp make a far better sea otter snack. And by zeroing in on those urchins, the otters keep the population in check, preventing urchins from scarfing up the remaining kelp.

Simply transplanting sea otters to new locations may create new challenges. That’s what happened off the Pacific Coast of Canada. Kelp forests there rebounded, but the otters competed with humans, especially Indigenous communities, that rely on the same food sources (SN: 6/11/20).

“The community on the North Coast is a very natural resource–dependent community, and this will impact them,” says Marissa Baskett, an ecologist at the University of California, Davis.

And there’s a lot of work to do to figure out how to bring back sunflower sea stars, now a critically endangered species. Nailing down the cause of the wasting syndrome, which is still unknown, will be crucial to recovery efforts.

Even so, understanding these interactions can provide clues to how to help restore the lost kelp forests, Baskett says. “These findings can inform restoration efforts aimed at recovering kelp forests and anticipating the effects of future marine heat waves.” More

Wearing waders and work gloves, three dozen employees from the U.S. Department of Agriculture’s Natural Resources Conservation Service stood at a small creek amid the dry sagebrush of southeastern Idaho. The group was eager to learn how to repair a stream the old­-fashioned way.

Tipping back his white cowboy hat, 73-year-old rancher Jay Wilde told the group that he grew up swimming and fishing at this place, Birch Creek, all summer long. But when he took over the family farm from his parents in 1995, the stream was dry by mid-June.

Wilde realized this was partly because his family and neighbors, like generations of American settlers before them, had trapped and removed most of the dam-building beavers. The settlers also built roads, cut trees, mined streams, overgrazed livestock and created flood-control and irrigation structures, all of which changed the plumbing of watersheds like Birch Creek’s.

Many of the wetlands in the western United States have disappeared since the 1700s. California has lost an astonishing 90 percent of its wetlands, which includes streamsides, wet meadows and ponds. In Nevada, Idaho and Colorado, more than 50 percent of wetlands have vanished. Precious wet habitats now make up just 2 percent of the arid West — and those remaining wet places are struggling.

Nearly half of U.S. streams are in poor condition, unable to fully sustain wildlife and people, says Jeremy Maestas, a sagebrush ecosystem specialist with the NRCS who organized that workshop on Wilde’s ranch in 2016. As communities in the American West face increasing water shortages, more frequent and larger wildfires (SN: 9/26/20, p. 12) and unpredictable floods, restoring ailing waterways is becoming a necessity.

Staff from the USDA Natural Resources Conservation Service pound posts to build a beaver dam analog across Birch Creek in Idaho in 2016. The effort gave nine relocated beavers a head start to create their own dam complexes.J. Maestas/USDA NRCS

Landowners and conservation groups are bringing in teams of volunteers and workers, like the NRCS group, to build low-cost solutions from sticks and stones. And the work is making a difference. Streams are running longer into the summer, beavers and other animals are returning, and a study last December confirmed that landscapes irrigated by beaver activity can resist wildfires.

Filling the sponge

Think of a floodplain as a sponge: Each spring, floodplains in the West soak up snow melting from the mountains. The sponge is then wrung out during summer and fall, when the snow is gone and rainfall is scarce. The more water that stays in the sponge, the longer streams can flow and plants can thrive. A full sponge makes the landscape better equipped to handle natural disasters, since wet places full of green vegetation can slow floods, tolerate droughts or stall flames.

Typical modern-day stream and river restoration methods can cost about $500,000 per mile, says Joseph Wheaton, a geomorphologist at Utah State University in Logan. Projects are often complex, and involve excavators and bulldozers to shore up streambanks using giant boulders or to construct brand-new channels.

“Even though we spend at least $15 billion per year repairing waterways in the U.S., we’re hardly scratching the surface of what needs fixing,” Wheaton says.

Big yellow machines are certainly necessary for restoring big rivers. But 90 percent of all U.S. waterways are small streams, the kind you can hop over or wade across.

For smaller streams, hand-built restoration solutions work well, often at one-tenth the cost, Wheaton says, and can be self-sustaining once nature takes over. These low-tech approaches include building beaver dam analogs to entice beavers to stay and get to work, erecting small rock dams or strategically mounding mud and branches in a stream. The goal of these simple structures is to slow the flow of water and spread it across the floodplain to help plants grow and to fill the underground sponge.

Less than a year after workers installed this hand-built rock structure, called a Zuni bowl, in an intermittent stream in southwestern Montana, erosion stopped moving upstream, keeping the grass above the structure green and lush.Sean Claffey/Southwest Montana Sagebrush Partnership

Fixes like these help cure a common ailment that afflicts most streams out West, including Birch Creek, Wheaton says: Human activities have altered these waterways into straightened channels largely devoid of debris. As a result, most riverscapes flow too straight and too fast.

“They should be messy and inefficient,” he says. “They need more structure, whether it’s wood, rock, roots or dirt. That’s what slows down the water.” Wheaton prefers the term “riverscape” over stream or river because he “can’t imagine a healthy river without including the land around it.”

Natural structures “feed the stream a healthy diet” of natural materials, allowing soil and water to accumulate again in the floodplain, he says.

Since as much as 75 percent of water resources in the West are on private land, conservation groups and government agencies like the NRCS are helping ranchers and farmers improve the streams, springs or wet meadows on their property.

“In the West, water is life,” Maestas says. “But it’s a very time-limited resource. We’re trying to keep what we have on the landscape as long as possible.”

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Beaver benefits

In watersheds across the West, beavers can be a big part of filling the floodplain’s sponge. The rodents gnaw down trees to create lodges and dams, and dig channels for transporting their logs to the dams. All this work slows down and spreads out the water.

On two creeks in northeastern Nevada, streamsides near beaver dams were up to 88 percent greener than undammed stream sections when measured from 2013 to 2016. Even better, beaver ponds helped maintain lush vegetation during the hottest summer months, even during a multiyear drought, Emily Fairfax, an ecohydrologist at California State University Channel Islands, and geologist Eric Small of University of Colorado Boulder reported in 2018 in Ecohydrology.

Satellite images show that when beavers settled into one part of Nevada’s Maggie Creek (bottom), digging channels to ferry in logs to build dams, the floodplain was wider, wetter and greener than an area of the creek with no dams (top).E. Fairfax/CSU Channel Islands

Satellite images show that when beavers settled into one part of Nevada’s Maggie Creek (bottom), digging channels to ferry in logs to build dams, the floodplain was wider, wetter and greener than an area of the creek with no dams (top).E. Fairfax/CSU Channel Islands

“Bringing beavers back just makes good common sense when you get down to the science of it,” Wilde says. He did it on his ranch.

Using beavers to restore watersheds is not a new idea. In 1948, for instance, Idaho Fish and Game biologists parachuted beavers out of airplanes, partly to improve trout habitat on public lands.

Wilde used trucks instead of parachutes. In 2015 and 2016, he partnered with the U.S. Forest Service and Idaho Fish and Game to livetrap and relocate nine beavers to Birch Creek from public lands about 120 kilometers away. To ensure the released rodents had a few initial ponds where they could escape from predators, Wilde worked with Anabranch Solutions, a riverscape restoration company cofounded by Wheaton and colleagues, to construct 26 beaver dam analogs. Would these simple branch-and-post structures entice the beavers to stay in Birch Creek?

It worked like a charm. In just three years, those beavers built 149 dams, transforming the once-narrow strip of green along the stream into a wide, vibrant floodplain. Birch Creek flowed 42 days longer, through the hottest part of the summer. Fish rebounded quickly too: Native Bonneville cutthroat trout populations were up to 50 times as abundant in the ponded sections in 2019 as they were when surveyed by the U.S. Forest Service in 2000, before beavers went to work.

“When you see the results, it’s almost like magic,” Wilde says. Even more magical, the transformation cost Wilde only “a couple hundred bucks in fence posts” and a few days of sweat equity, thanks in part to those NRCS staffers who came in 2016 and a host of volunteers.

Rock dams in the desert

Beaver-powered restoration isn’t the answer everywhere, especially in the desert where creeks are ephemeral, flowing only intermittently. In Colorado’s Gunnison River basin, ranchers were looking for ways to boost water availability to ensure their cattle had enough drinking water and green grass in the face of climate change. Meanwhile, the area’s public land managers wanted to restore streams to help at-risk wildlife species like the Gunnison sage grouse, once prolific across sagebrush country.

In 2012, a group of private landowners, public agencies and nonprofit organizations launched the Gunnison Basin Wet Meadow and Riparian Restoration and Resilience-building Project to revive streams and keep meadows green. The group hired Bill Zeedyk to instruct on how to build simple, low-profile dams by stacking rocks, known widely as Zeedyk structures, to slow down the water.

Zeedyk, now 85, runs his own wetland and stream restoration firm in New Mexico, after 34 years as a wildlife biologist at the U.S. Forest Service. His 2014 book Let the Water Do the Work has inspired people across the West — including Maestas and Wheaton — to turn to simple, nature-based stream restoration solutions.

Over the last nine years, Zeedyk has helped the Gunnison collaborative build nearly 2,000 rock structures throughout the roughly 10,000-square-kilometer upper Gunnison watershed. The group has restored 43 kilometers of stream and improved nearly 500 hectares of wet habitat for people and wildlife. A typical project involves a dozen volunteers working for a day or two in one creek bottom where they build dozens of rock structures.

In 2017, Maestas asked Zeedyk to show more than 100 people involved in the NRCS-led Sage Grouse Initiative how to install rock structures. The white-bearded Zeedyk led them along an eroding gully near Gunnison that June.

Conservation professionals gathered in Gunnison, Colo., in 2017 to learn how to build Zeedyk structures, simple rock dams that slow the flow of water in small creeks to increase surrounding plant growth.B. Randall

Lifting his wooden walking staff, Zeedyk pointed out how the adjacent dirt road originally created by horses and wagons cut off the creek from its historic floodplain. The road made the channel shorter, straighter and steeper over time. “There’s less growing space, and the whole system is less productive,” he explained.

As participants decided where to stack rocks to spread water across the dusty sagebrush flat, Zeedyk encouraged them to “read the landscape” and “think like water.” After three hours of work, participants could already see ponds forming behind their rock creations.

Watching the teams work and laugh together, Maestas called it the aha moment for the crew. “When you get your hands dirty, there’s a degree of buy-in that can’t come from sitting in a classroom or reading about it.”

The grass is greener

The hope is that, like the beaver dam analogs, these hand-built rock structures will halt erosion, capture sediment, fill the floodplain sponge and grow more water-loving plants.

Patience, Zeedyk says, is crucial. “After we put natural processes into play in a positive direction, we have to wait for the water to do its work.”

The wait isn’t necessarily long. At four of the sites in the Gunnison basin restored with Zeedyk structures, wetland plant cover (including sedges, rushes, willows and wetland forbs) increased an average of 160 percent four years post-treatment, compared with a 15 percent average increase at untreated areas near each study site, according to a 2017 report by The Nature Conservancy.

“As of 2019, we had increased the wetland species cover by 200 percent in six years,” says Renee Rondeau, an ecologist at the Colorado Natural Heritage Program, based in Hesperus. “So great to see this success.”

Animals seem to enjoy all that fresh green growth too. Colorado Parks and Wildlife set up remote cameras to monitor whether wildlife use the restored floodplain. Since 2016, the cameras have captured more than 1.5 million images, most of which show a host of animals — from cattle and elk to sage grouse and voles — munching away in the now-lush meadows. A graduate student at Western Colorado University is classifying photos to determine whether there’s a significant difference in the number of Gunnison sage grouse at the restored sites compared with adjacent untreated areas.

“Sage grouse chicks chase the green line as the desert dries up,” Maestas explains. After hatching in June, hens and their broods seek out wet areas where chicks stock up on protein-rich insects and wildflowers to grow and survive the winter.

A remote camera spies Gunnison sage grouse feasting on insects and plants in a wet meadow. The area stays green long into the summer because of hand-built rock dams that spread water across the land.Courtesy of Nathan Seward/Colorado Parks and Wildlife

Water in the bank

The Gunnison basin is not the only place where sticks-and-stones restoration is paying dividends for people and wildlife. Nick Silverman, a hydroclimatologist and geospatial data scientist, and his colleagues at the University of Montana in Missoula used satellite imagery to evaluate changes in “greenness” at three sites that used different simple stream restoration treatments: Zeedyk’s rock structures in Gunnison, beaver dam analogs in Oregon’s Bridge Creek and fencing projects that kept livestock away from streambanks in northeastern Nevada’s Maggie Creek.

Late summer greenness increased up to 25 percent after streams were restored compared with before, the researchers reported in 2018 in Restoration Ecology. Plus, the streams showed greater resilience to climate variability as time went on: Along Maggie Creek, restored more than two decades before the study, the plants stayed green even when rainfall was low, and the area had substantial increases in plant production during late summer, when vegetation usually dries out.

“It’s like putting water in a piggy bank when it’s wet, so plants and animals can withdraw it later when it’s dry,” Silverman says. Even more exciting, he adds, is that the impact of the low-cost options is large enough to see from space.

Water doesn’t burn

The Sharps Fire that scorched south-central Idaho in July 2018 burned a wide swath of a watershed where Idaho Fish and Game had relocated beavers to restore a floodplain. A strip of wet, green vegetation stood untouched along the beavers’ ponds. Wheaton sent a drone to take photos, tweeting out an image on September 5, 2018: “Why is there an impressive patch of green in the middle of 65,000 acres of charcoal? Turns out water doesn’t burn. Thank you beaver!”

The green strip of vegetation along beaver-made ponds in Baugh Creek near Hailey, Idaho, resisted flames when a wildfire scorched the region in 2018, as shown in this drone image.J. Wheaton/Utah State Univ.

Fairfax, the ecohydrologist who reported that beaver dams increase streamside greenness, had been searching for evidence that beavers could help keep flames at bay. Wheaton’s tweet was a “kick in the pants to push my own research on beavers and fire forward,” she says.

With undergraduate student Andrew Whittle, now at the Colorado School of Mines, Fairfax got to work analyzing satellite imagery from recent wildfires. The two mapped thousands of beaver dams within wildfire-burned areas in several western states. Choosing five fires of varying severity in both shrubland and forested areas, the pair analyzed the data to see if creeks with beaver activity stayed greener than creeks without beavers during wildfires.

[embedded content]
Emily Fairfax produced this stop-motion video to show how beavers and their dams and channels keep water in an area, supporting the surrounding vegetation and helping the area resist wildfires.

“Across the board, beaver-dammed areas didn’t burn,” Fairfax says. The study was published last December in Ecological Applications during one of the West’s worst fire seasons. It garnered plenty of attention from land managers asking for more specifics, like how many beavers are needed to buffer a fire.

Fairfax plans to study several more burned sites with beaver ponds. She hopes to eventually create a statistical model that can help people plan nature-powered stream restoration projects.

“When we’re seeing hotter, more unpredictable fires that are breaking all the rules we know of,” Fairfax says, “we have to figure out how to preserve critical wet habitats.” More

The emergency surgery took place in the back of a modified pickup truck in a McDonald’s parking lot in Pikeville, Ky. This scrappy plan to rescue a species of mussel on the edge of extinction made perfect sense: Meet somewhere between Indian Creek in Virginia, where the last known wild golden riffleshells lived, and Kentucky’s Center for Mollusk Conservation in Frankfort, where they would be saved.
The strategy was a malacologist’s version of a Hail Mary pass. One scientist would gingerly pry open three golden riffleshells and remove their larvae to be nurtured in his lab. The other would return the three mussels to Indian Creek, and wait for the day he could introduce their grown offspring to the same habitat. If the plan didn’t produce enough offspring to sustain a new population, the mussels would probably vanish.
Five years ago, Indian Creek was the only known remaining habitat for the golden riffleshell (Epioblasma florentina aureola). And like many other mussels, this bivalve’s future looked bleak. Biologists estimated that only about 100 remained in the wild. “They were the next species on the list for disappearing from the face of the Earth,” says biologist Tim Lane, who leads mussel recovery efforts at the Virginia Department of Wildlife Resources’ Aquatic Wildlife Conservation Center, near Marion. “We were literally watching the last of them.”
Seeing a species vanish in real time is difficult, he says, and is in some ways worsened by the mussels’ near-invisibility beneath the surface. “They’re not charismatic like, say, the northern white rhino,” he says. When mussels go extinct, almost no one knows — or mourns them.
The survival of mussel 6420 and thousands of its siblings started with an interstate rescue plan hatched by biologist Tim Lane.Gary Peeples/USFWS
An avid amateur photographer who takes pictures of mollusks, snails, fish and various other small critters in the wild, Lane spends much of his time floating facedown in Appalachian waterways, suspended over rocky riverbeds like a float in the Macy’s Thanksgiving Day Parade. He came up with the plan and carried out phase one: delicately prying the bivalves from the Indian Creek river-bed and laying them in a cooler filled with pebbles, dirt and river water for the 90-minute trip to Kentucky.
A full-grown golden riffleshell is about the size of a small biscuit, with a yellowy, fan-shaped case. Like other mussels, it anchors itself in gravel with a fleshy foot and rarely moves more than a few meters during its lifetime, which could last 15 years or more. The sedentary creatures have been listed as a federally endangered species since 1977.
Malacologists, like Lane and others who study mollusks, are accustomed to championing underdogs. More than two-thirds of all identified North American freshwater mussel species are extinct or endangered. North America has the greatest diversity of freshwater mussels — with a heavy concentration in the Southeast. Tennessee’s Clinch River hosts about twice as many species as all of Europe.

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In every locale, the mussels’ problems arise from a mix of factors. Until about a century ago, enormous mussel populations thrived in the Midwest and Southeast, and mussels were often harvested to make shell buttons. But the construction of dams in major rivers divided these populations and separated the creatures from the fish that carry their larvae. “The dams suffocated the huge mussel beds in the most productive habitats,” says Paul Johnson, who runs Alabama’s Aquatic Biodiversity Center, in Perry County.
Adding insult to injury, rampant pollution from industrial dumping and chemical spills led to massive die-offs before the 1972 Clean Water Act led to cleaner waterways. The animals have faced other threats, too, including microbial pathogens and predators.
Just last December, more than 150 kilometers downstream of the confluence of Indian Creek and the Clinch, biologists with the U.S. Fish and Wildlife Service reported a massive die-off of pheasantshells (Actinonaias pectorosa) where the river passes through the town of Kyles Ford, Tenn. The researchers suspect some pathogenic fungi, bacteria or parasites are to blame. Myriad species in Europe and the Pacific Northwest, including the freshwater pearl mussel (Margaritifera margaritifera) and the depressed river mussel (Pseudanodonta complanata), have experienced similar die-offs.
Against that backdrop of known and unknown hazards, researchers around the world are combining in vitro propagation, months of tedious observation and exhaustive laboratory trial and error to save these animals. But none of these evolving methods offer a quick fix.
“It took us 100 years to get into this mess,” Johnson says. “It’s not going to take 10 to get out of it.”
A small group of biologists is getting creative to save freshwater mussels, animals that do a yeoman’s job of cleaning rivers.Gary Peeples/USFWS
River cleaners
Those who study and try to save mussels feel an irresistible calling, says Jessi DeMartini, a biologist in Illinois who works on mussel conservation in the Forest Preserve District of DuPage County. “It’s an addiction … that becomes a passion.” They see mollusks as the uncelebrated heroes of the world’s rivers.
Mollusk shells stabilize riverbeds and create habitats for other creatures. The bivalves provide food to raccoons, muskrats and other critters. Most importantly, mollusks are nature’s water filters, able to clean up big messes.
A single mussel can filter more than 50 liters of water per day, removing algae and pollution, including toxic substances dumped into rivers as industrial waste. Some researchers suspect that the ability to sop up toxic metals is contributing to the animals’ decline. Like canaries in coal mines, if a mussel population suddenly plummets, it’s a sign that something’s gone foul in the water. (Malacologists describe the smell of a living mussel as rich and sweet, like the river it comes from. But find a dead mussel and the stench is so bad you’d wish you had been born without a sense of smell.)

By observing the health of juvenile mussels and analyzing tissue samples, researchers can effectively monitor water quality and acute die-offs, Monte McGregor, director of Kentucky’s Center for Mollusk Conservation, and others reported in December 2019 in Freshwater Science.
The effort to save mussels has implications far beyond the rural and rugged riverways of Appalachia. More than two-thirds of U.S. homes get their drinking water from rivers, Johnson notes. Mussels provide an inexpensive way to safeguard that resource and do some of the work of water treatment plants. “Mussels allow us to provide cleaner water on a less per-cost basis,” he says.
For all these reasons, conservation biologists keep returning to the rivers and take hope where they can find it. The golden riffleshell has been particularly vexing. To even begin the process of mussel propagation, which has a high rate of failure, biologists typically need to start with larvae, also known as glochidia. The golden riffleshell’s dwindling numbers mean that finding a gravid female — one filled with glochidia — is a rare occasion. But on an April morning in 2016, hope came with a find by Sarah Colletti, a mussel-loving biologist also at Virginia’s Aquatic Wildlife Conservation Center. Colletti had joined a small squad of biologists who donned tall rubber waders and spent hours hunched over viewscopes, which look like toy telescopes, pointed down into water to make it easy to tell rocks from mussels. Colletti was scanning the bottom of Indian Creek as part of what’s become an annual ritual, the search for the last remaining golden riffleshells.
Biologist Sarah Colletti found three gravid golden riffleshell females in Virginia’s Indian Creek in 2016, setting off a chain of events that might give the endangered species a chance at survival.G. Peeples/USFWS
It’s a monotonous pursuit, she says, and “you’re second-guessing every rock.” When a mussel comes into view, “it’s kind of shocking.”
Through her viewscope, Colletti spotted three golden riffleshells nestled among the rocks and silt. All were females displaying their lure, a section of tissue that resembles a tasty meal. Those exposed lures meant the mussels were gravid, ready to release millions of glochidia. Finding three gravid females was unusual. The biologists saw an opportunity — maybe one of the last — to help.
Alluring display
Just getting to the larval stage is an accomplishment for these bivalves. Eggs become fertilized only when females filter sperm released into the water by upstream males.
Glochidia, each the size of a grain of salt, can’t survive on their own. They have to clamp onto the gills of a host fish and become parasitic passengers, embedding themselves in the gill tissue and thriving on a mix of nutrients in the water and in fish blood until undergoing a kind of metamorphosis.
As mussels grow their first shells and become juveniles, they swell to the size of a well-fed deer tick, then drop from the fish. For each species of mussel, there’s often only one — or at most, a few — species of fish that can ferry larvae to the next stage of life.
Mussels have evolved a staggering array of methods for infesting fish; almost all involve deception. Some mussels disguise their glochidia in alluring packages that look like minnows; others unspool wormlike appendages tipped with packets holding millions of larvae. The rainbow mussel (Villosa iris) has a lure that looks like a crawfish skittering along the river floor. When a fish tries to eat the minnow or worm or crawfish, the fish gets a mouthful of glochidia, released like dandelion seeds. With the fish’s next gulp of water, the glochidia wash over the gills and stick.
What looks like a tasty, spotted minnow is actually part of a Lampsilis mussel. When a fish goes in for a bite of this lure, it inhales a mouthful of mussel larvae that attach to the fish’s gills and grow into juveniles.M. Christopher Barnhart
Members of the genus Epioblasma, including the golden riffleshell, have perfected a tactic that earned them the nickname “fish snapper.” The ritual begins when a mother mussel sends out a short thread, the end of which looks like a bug. When a hungry fish swims in for a bite, the shell snaps shut around the fish’s head and holds tight with short, sharp teeth just inside the shell’s rim. As the fish chokes, it inhales the glochidia, which install themselves in the gills. After a few minutes, the mussel relaxes and releases its captive. The fish that survive are stunned; smaller fish (which aren’t good hosts anyway) may die, their heads crushed by the mollusk’s snap.
The handoff
All the pieces of this choreographed sequence — fertilization to glochidia formation to infestation of a host — have to happen in just the right way, says McGregor, who with fellow Kentucky biologist Leroy Koch was waiting at the McDonald’s for Lane to arrive. “There are lots of strikes against these mussels,” he says. “The glochidia have to hit the right fish at the right time.”
Ideally, mussels would reproduce on their own and people wouldn’t have to intervene. Malacologists step in when a species looks like it’s on the brink of extinction.

A snuffbox mussel snaps shut on the head of a rainbow darter, giving the snuffbox larvae, or glochidia, enough time to attach to the fish’s gills.M. Christopher Barnhart
A closeup photo shows nearly clear glochidia of an oyster mussel attached to the pink gills of a logperch.M. Christopher Barnhart

That morning in April, Colletti marked the location of the mussels in the stream with three large stones and a bright orange flag. She phoned Lane, who had spent much of graduate school studying the diversity of life in Appalachian rivers. The golden riffleshell always seemed to be foundering. In previous years, when they found gravid females in Indian Creek, Lane and colleagues had attempted streamside infestations: catching host fish and manually transferring glochidia from the mussel into the fish gills. But the approach didn’t work.
Lane called McGregor, who was well-known in the close-knit malacology community for having pioneered in vitro approaches to bring bivalves back. Biologists have sent him glochidia in test tubes via UPS and FedEx; he’s also been known to drive for hours to secure the larvae. At Kentucky’s Center for Mollusk Conservation, he closely monitors the temperature and quality of the water that flows through the lab, and he makes his own food for the mussels — often customizing a recipe to fit the needs of a species. After Lane called and proposed the plan, McGregor agreed to meet in Pikeville and carry out the glochidia-removing procedure in what he calls his “mobile lab” (the topped bed of his Ford F-250 super duty crew cab).
Surgery took no more than 30 minutes per mussel. McGregor pried open the shell about five millimeters with his fingers, and used a silicone wedge to keep it open. Then, he filled a syringe with sterile water and flushed out the glochidia from the mussels into a lab dish. All the while, he had to pay attention to the patient and keep it cool.
 “You have to handle the mussel properly,” McGregor says. If the animal gets too warm, that could imperil both the larvae and the mother.
Once the procedure was over, Lane replaced the mussels in the cooler and drove east to return them to Indian Creek. McGregor drove west, escorting thousands of golden rifflleshell larvae over 260 kilometers of twisting mountain roads, to the mussel recovery operation with the longest track record for propagating mussels in the lab without host fish. This would be the golden riffleshell’s best chance at survival.
Take me to the river
For nearly 20 years, researchers at the Kentucky facility have worked on bringing mussels back from the brink of extinction. The small collection of buildings sits near Elkhorn Creek, but McGregor says the water is often too polluted to use for the tanks that hold mussels during the most sensitive part of their development. The pollutants include raw sewage. “We can’t grow mussels in raw sewage,” he says.
If such a thing as “artisanal algae” exists, it’s surely the stuff grown in this lab. Researchers grow algal cultures in giant incubators. McGregor has grown many algal varieties and has spent years matching the right algal slime to the right mussel.

Biologists have developed methods of propagating endangered mussel species in the lab, even without the host fish. To remove glochidia, scientists first pry open the shell.T. Lane
Then a scientist holds open the mussel shell with a silicone wedge to flush out the larvae with sterile water.T. Lane

McGregor learned the basics of in vitro propagation in 2004 from Robert Hudson, a malacologist at Presbyterian College in Clinton, S.C. By 2016, McGregor had spent more than a decade improving his recipe, finding the right mix of algae, nutrients and rabbit serum to feed glochidia. Although he prefers to use host fish to grow mussels — and the lab contains dozens of tanks that hold fish as hosts for some other species — scientists have so far been unable to identify the fish that can carry golden riffleshell larvae (which is why streamside infestation doesn’t work).
So McGregor had to grow the larvae without a host. After 18 days in an incubator with McGregor’s custom-made mussel-growing cocktail, about 1,600 larvae survived to become juveniles. They were transferred to silt-lined raceways with cool flowing water to simulate a river. Within a few months, the glochidia had grown to the size of nickels — large enough to survive in the wild.
McGregor divided the spoils. “It was too risky for me to keep them all,” he says. He sent groups of mussels back over the mountains to two facilities in Virginia. One is the Aquatic Wildlife Conservation Center, where Colletti and colleagues have been studying and cultivating the bivalves. In a typical year, researchers there release up to 10,000 lab-grown mussels into the wild, representing up to 10 species.
Colletti says she sees signs of hope for the golden riffleshell. Today, the progeny of those three mussels she found in 2016 are producing their own glochidia in the lab. “They were able to become gravid in captivity,” she says. Lane recently sent photos of those larval grandchildren to McGregor. Colletti and Lane hope the young mussels released into the river will do as well.
There are other, scattered success stories emerging from recent mussel projects. Johnson, in Alabama, has spent years studying the pale lilliput (Toxolasma cylindrellus).
After more than two years of work, Johnson pegged the northern studfish (Fundulus catenatus), which looks like a larger, prettier version of a minnow, as the pale lilliput’s host. Once he made that connection, Johnson began to infest a host fish to cultivate new populations of the endangered species.
There are also big risks. Last year, Johnson propagated about 5,000 juveniles of the rare Louisiana pearshell mussel (Margaritifera hembeli). But just before he was going to release juveniles into a Louisiana river, disaster struck. On an unusually hot spring morning, the temperature of the water streaming into his facility’s raceways soared, killing thousands of the mussels before a researcher could close the valve. “One bad day can literally wreck several years of work,” Johnson says.
He was left with only about 100 animals to return to nature. But those animals have been thriving in the lab. Johnson has grown new batches and plans to restore them to their natural habitat next year. It’s too soon to declare victory, he says, but he’s hopeful.
This gravid golden riffleshell began as a larva in Indian Creek, grew up in a Kentucky lab and is now in a Virginia lab. Its parted shell reveals pouches containing tiny larvae ready to infest an unwitting host fish.T. Lane
The ultimate goal in mussel conservation, Johnson says, is to propagate animals that can complete an entire life cycle. That means glochidia get to the host fish, survive the tumultuous juvenile years and mature enough to reproduce. In the wild, the whole process takes a few weeks to a few months. In the lab, the timescale is bigger. “It’s a decadeslong effort,” he says.
Hundreds of the next generation of golden riffleshells are now back at home, with two populations in the Clinch River and one in Indian Creek since 2017. These mussels now measure about the size of a quarter, though some are bigger. Of the 700 that Lane, Colletti and others installed in the wild, many have died and some are unaccounted for, but the researchers estimate that about 300 are still alive.
The scientists placed transponders on about 100 of the mussels, and every year Lane and Colletti return for a census, waving a device that looks like a metal detector over the water surface and waiting for the satisfying chirp that indicates a lab-grown riffleshell is found.
For now, the rescue of the golden riffleshell remains a good news story, but Lane says malacologists have to remain vigilant. “This gives us some time, but it’s not like we can pat ourselves on the back and stop.” To ensure the survival of the species, biologists will need to continue harvesting glochidia, shepherding mussels to the juvenile stage and returning them to the wild, year after year. The ultimate goal is to build a population that can sustain itself and reproduce without human intervention, rabbit serum or emergency surgery outside a rural McDonald’s. More