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    How kelp forests off California are responding to an urchin takeover

    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

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    Simple hand-built structures can help streams survive wildfires and drought

    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

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    To save Appalachia’s endangered mussels, scientists hatched a bold plan

    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

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