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    Rivers might not be as resilient to drought as once thought

    Rivers ravaged by a lengthy drought may not be able to recover, even after the rains return. Seven years after the Millennium drought baked southeastern Australia, a large fraction of the region’s rivers still show no signs of returning to their predrought water flow, researchers report in the May 14 Science.

    There’s “an implicit assumption that no matter how big a disturbance is, the water will always come back — it’s just a matter of how long it takes,” says Tim Peterson, a hydrologist at Monash University in Melbourne, Australia. “I’ve never been satisfied with that.”

    The years-long drought in southeastern Australia, which began sometime between 1997 and 2001 and lasted until 2010, offered a natural experiment to test this assumption, he says. “It wasn’t the most severe drought” the region has ever experienced, but it was the longest period of low rainfall in the region since about 1900.

    Peterson and colleagues analyzed annual and seasonal streamflow rates in 161 river basins in the region from before, during and after the drought. By 2017, they found, 37 percent of those river basins still weren’t seeing the amount of water flow that they had predrought. Furthermore, of those low-flow rivers, the vast majority — 80 percent — also show no signs that they might recover in the future, the team found.

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    Many of southeastern Australia’s rivers had bounced back from previous droughts, including a severe but brief episode in 1983. But even heavy rains in 2010, marking the end of the Millennium drought, weren’t enough to return these basins to their earlier state. That suggests that there is, after all, a limit to rivers’ resilience.

    What’s changed in these river basins isn’t yet clear, Peterson says. The precipitation post drought was similar to predrought precipitation, and the water isn’t ending up in the streamflow, so it must be going somewhere else. The team examined various possibilities: The water infiltrated into the ground and was stored as groundwater, or it never made it to the ground at all — possibly intercepted by leaves, and then evaporating back to the air.

    But none of these explanations were borne out by studies of these sites, the researchers report. The remaining, and most probable, possibility is that the environment has changed: Water is evaporating from soils and transpiring from plants more quickly than it did predrought.

    Peterson has long suggested that under certain conditions rivers might not, in fact, recover — and this study confirms that theoretical work, says Peter Troch, a hydrologist at the University of Arizona in Tucson. Enhanced soil evaporation and plant transpiration are examples of such positive feedbacks, processes that can enhance the impacts of a drought. “Until his work, this lack of resilience was not anticipated, and all hydrological models did not account for such possibility,” Troch says.

    “This study will definitely inspire other researchers to undertake such work,” he notes. “Hopefully we can gain more insight into the functioning of [river basins’] response to climate change.”

    Indeed, the finding that rivers have “finite resilience” to drought is of particular concern as the planet warms and lengthier droughts become more likely, writes hydrologist Flavia Tauro in a commentary in the same issue of Science. More

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    A common antibiotic slows a mysterious coral disease

    Slathering corals in a common antibiotic seems to temporarily soothe a mysterious tissue-eating disease, new research suggests.

    Just off Florida, a type of coral infected with stony coral tissue loss disease, or SCTLD, showed widespread improvement several months after being treated with amoxicillin, researchers report April 21 in Scientific Reports. While the deadly disease eventually reappeared, the results provide a spot of good news while scientists continue the search for what causes it.

    “The antibiotic treatments give the corals a break,” says Erin Shilling, a coral researcher at Florida Atlantic University’s Harbor Branch Oceanographic Institute in Fort Pierce. “It’s very good at halting the lesions it’s applied to.”

    Divers discovered SCTLD on reefs near Miami in 2014. Characterized by white lesions that rapidly eat away at coral tissue, the disease plagues nearly all of the Great Florida Reef, which spans 580 kilometers from St. Lucie Inlet in Marin County to Dry Tortugas National Park beyond the Florida Keys. In recent years, SCTLD has spread to reefs in the Caribbean (SN: 7/9/19).

    As scientists search for the cause, they are left to treat the lesions through trial and error. Two treatments that show promise involve divers applying a chlorinated epoxy or an amoxicillin paste to infected patches. “We wanted to experimentally assess these techniques to see if they’re as effective as people have been reporting anecdotally,” Shilling says.In April 2019, Shilling and colleagues identified 95 lesions on 32 colonies of great star coral (Montastraea cavernosa) off Florida’s east coast. The scientists dug trenches into the corals around the lesions to separate diseased tissue from healthy tissue, then filled the moats and covered the diseased patches with the antibiotic paste or chlorinated epoxy and monitored the corals over 11 months.

    Treatment with an amoxicillin paste (white bands, left) stopped a tissue-eating lesion from spreading over a great star coral colony up to 11 months later (right).E.N. Shilling, I.R. Combs and J.D. Voss/Scientific Reports 2021

    Within about three months of the treatment, some 95 percent of infected coral tissues treated with amoxicillin had healed. Meanwhile, only about 20 percent of infected tissue treated with chlorinated epoxy had healed in that time — no better than untreated lesions. 

    But a one-and-done treatment doesn’t stop new lesions from popping up over time, the team found. And some key questions remain unanswered, the scientists note, including how the treatment works on larger scales and what, if any, longer-term side effects the antibiotic could have on the corals and their surrounding environment.“Erin’s work is fabulous,” says Karen Neely, a marine biologist at Nova Southeastern University in Fort Lauderdale, Fla. Neely and her colleagues see similar results in their two-year experiment at the Florida National Marine Sanctuary. The researchers used the same amoxicillin paste and chlorinated epoxy treatments on more than 2,300 lesions on upwards of 1,600 coral colonies representing eight species, including great star coral.Those antibiotic treatments were more than 95 percent effective across all species, Neely says. And spot-treating new lesions that popped up after the initial treatment appeared to stop corals from becoming reinfected over time. That study is currently undergoing peer-review in Frontiers in Marine Science.

    “Overall, putting these corals in this treatment program saves them,” Neely says. “We don’t get happy endings very often, so that’s a nice one.” More

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    Mangrove forests on the Yucatan Peninsula store record amounts of carbon

    Coastal mangrove forests are carbon storage powerhouses, tucking away vast amounts of organic matter among their submerged, tangled root webs.

    But even for mangroves, there is a “remarkable” amount of carbon stored in small pockets of forest growing around sinkholes on Mexico’s Yucatan Peninsula, researchers report May 5 in Biology Letters. These forests can stock away more than five times as much carbon per hectare as most other terrestrial forests.

    There are dozens of mangrove-lined sinkholes, or cenotes, on the peninsula. Such carbon storage hot spots could help nations or companies achieve carbon neutrality — in which the volume of greenhouse gas emissions released into the atmosphere is balanced by the amount of carbon sequestered away (SN: 1/31/20).

    At three cenotes, researchers led by Fernanda Adame, a wetland scientist at Griffith University in Brisbane, Australia, collected samples of soil at depths down to 6 meters, and used carbon-14 dating to estimate how fast the soil had accumulated at each site. The three cenotes each had “massive” amounts of soil organic carbon, the researchers report, averaging about 1,500 metric tons per hectare. One site, Casa Cenote, stored as much as 2,792 metric tons per hectare.

    Mangrove roots make ideal traps for organic material. The submerged soils also help preserve carbon. As sea levels have slowly risen over the last 8,000 years, mangroves have kept pace, climbing atop sediment ported in from rivers or migrating inland. In the cave-riddled limestone terrain of the Yucatan Peninsula, there are no rivers to supply sediment. Instead, “the mangroves produce more roots to avoid drowning,” which also helps the trees climb upward more quickly, offering more space for organic matter to accumulate, Adame says.

    As global temperatures increase, sea levels may eventually rise too quickly for mangroves to keep up (SN: 6/4/20). Other, more immediate threats to the peninsula’s carbon-rich cenotes include groundwater pollution, expanding infrastructure, urbanization and tourism. More

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    These climate-friendly microbes recycle carbon without producing methane

    Earth’s hot springs and hydrothermal vents are home to a previously unidentified group of archaea. And, unlike similar tiny, single-celled organisms that live deep in sediments and munch on decaying plant matter, these archaea don’t produce the climate-warming gas methane, researchers report April 23 in Nature Communications.

    “Microorganisms are the most diverse and abundant form of life on Earth, and we just know 1 percent of them,” says Valerie De Anda, an environmental microbiologist at the University of Texas at Austin. “Our information is biased toward the organisms that affect humans. But there are a lot of organisms that drive the main chemical cycles on Earth that we just don’t know.”

    Archaea are a particularly mysterious group (SN: 2/14/20). It wasn’t until the late 1970s that they were recognized as a third domain of life, distinct from bacteria and eukaryotes (which include everything else, from fungi to animals to plants).

    For many years, archaea were thought to exist only in the most extreme environments on Earth, such as hot springs. But archaea are actually everywhere, and these microbes can play a big role in how carbon and nitrogen cycle between Earth’s land, oceans and atmosphere. One group of archaea, Thaumarchaeota, are the most abundant microbes in the ocean, De Anda says (SN: 11/28/17). And methane-producing archaea in cows’ stomachs cause the animals to burp large amounts of the gas into the atmosphere (SN: 11/18/15).

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    Now, De Anda and her colleagues have identified an entirely new phylum — a large branch of related organisms on the tree of life — of archaea. The first evidence of these new organisms were within sediments from seven hot springs in China as well as from the deep-sea hydrothermal vents in the Guaymas Basin in the Gulf of California. Within these sediments, the team found bits of DNA that it meticulously assembled into the genetic blueprints, or genomes, of 15 different archaea.

    The researchers then compared the genetic information of the genomes with that of thousands of previously identified genomes of microbes described in publicly available databases. But “these sequences were completely different from anything that we know,” De Anda says.

    She and her colleagues gave the new group the name Brockarchaeota, for Thomas Brock, a microbiologist who was the first to grow archaea in the laboratory and who died in April. Brock’s discovery paved the way for polymerase chain reaction, or PCR, a Nobel Prize–winning technique used to copy small bits of DNA, and currently used in tests for COVID-19 (SN: 3/6/20).

    Brockarchaeota, it turns out, actually live all over the world — but until now, they were overlooked, undescribed and unnamed. Once De Anda and her team had pieced together the new genomes and then hunted for them in public databases, they discovered that bits of these previously unknown organisms had been found in hot springs, geothermal and hydrothermal vent sediments from South Africa to Indonesia to Rwanda.

    Within the new genomes, the team also hunted for genes related to the microbes’ metabolism — what nutrients they consume and what kind of waste they produce. Initially, the team expected that — like other archaea previously found in such environments — these archaea would be methane producers. They do munch on the same materials that methane-producing archaea do: one-carbon compounds like methanol or methylsulfide. “But we couldn’t identify the genes that produce methane,” De Anda says. “They are not present in Brockarchaeota.”

    That means that these archaea must have a previously undescribed metabolism, through which they can recycle carbon — for example in sediments on the seafloor — without producing methane. And, given how widespread they are, De Anda says, these organisms could be playing a previously hidden but significant role in Earth’s carbon cycle.

    “It’s twofold interesting — it’s a new phylum and a new metabolism,” says Luke McKay, a microbial ecologist of extreme environments at Montana State University in Bozeman. The fact that this entire group could have remained under the radar for so long, he adds, “is an indication of where we are in the state of microbiology.”

    But, McKay adds, the discovery is also a testimonial to the power of metagenomics, the technique by which researchers can painstakingly tease apart individual genomes out of a large hodgepodge of microbes in a given sample of water or sediments. Thanks to this technique, researchers are identifying more and more parts of the previously mysterious microbial world.

    “There’s so much out there,” De Anda says. And “every time you sequence more DNA, you start to realize that there’s more out there that you weren’t able to see the first time.” More

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    Climate change may have changed the direction of the North Pole’s drift

    A sudden zag in which way the North Pole was drifting in the 1990s probably stemmed in large part from glacial melt caused by climate change, a new study suggests.

    The locations of Earth’s geographic poles, where the planet’s axis pierces the surface, aren’t fixed. Instead, they wander in seasonal and near-annual cycles, largely driven by weather patterns and ocean currents (SN: 4/15/03). But in addition to moving about in relatively tight swirls just a few meters across, the poles drift over time as the planet’s weight distribution shifts and alters its rotation around its axis.

    Before the mid-1990s, the North Pole had been drifting toward the western edge of Canada’s Ellesmere Island. But then the pole veered eastward by about 71 degrees toward the northeastern tip of Greenland. It’s continued to head that way, moving about 10 centimeters per year. Scientists aren’t quite sure why this shift occurred, says Suxia Liu, a hydrologist at the Institute of Geographic Sciences and Natural Resources Research in Beijing.

    Liu and colleagues checked how well the polar drift trends matched data from previous studies on glacial melt worldwide. In particular, glacier melt in Alaska, Greenland and the southern Andes accelerated in the 1990s (SN: 9/30/20). The timing of that melting, as well as the effects it would have had on Earth’s mass distribution, suggests that glacial melt induced by climate change helped trigger the change in polar drift, the team reports in the April 16 Geophysical Research Letters.

    The team’s analysis shows that while glacier melting can account for much of the change in polar drift, it doesn’t explain all of it. So other factors must be at play. With copious irrigation, for example, groundwater pumped from aquifers in one region can end up in an ocean far away (SN: 10/9/19). Like glacial melt, water management alone can’t explain the North Pole’s tack, the team reports, but it can give the Earth’s axis a substantial nudge.

    The findings “reveal how much human activity can have an impact on changes to the mass of water stored on land,” says Vincent Humphrey, a climate scientist at the University of Zurich not involved in this study. And they show how large these mass shifts can be, he says. “They’re so big that they can change the axis of the Earth.” More

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    A new technique could make some plastic trash compostable at home

    A pinch of polymer-munching enzymes could make biodegradable plastic packaging and forks truly compostable.

    With moderate heat, enzyme-laced films of the plastic disintegrated in standard compost or plain tap water within days to weeks, Ting Xu and her colleagues report April 21 in Nature.

    “Biodegradability does not equal compostability,” says Xu, a polymer scientist at the University of California, Berkeley and Lawrence Berkeley National Laboratory. She often finds bits of biodegradable plastic in the compost she picks up for her parents’ garden. Most biodegradable plastics go to landfills, where the conditions aren’t right for them to break down, so they degrade no faster than normal plastics.

    Embedding polymer-chomping enzymes in biodegradable plastic should accelerate decomposition. But that process often inadvertently forms potentially harmful microplastics, which are showing up in ecosystems across the globe (SN: 11/20/20). The enzymes clump together and randomly snip plastics’ molecular chains, leading to an incomplete breakdown. “It’s worse than if you don’t degrade them in the first place,” Xu says.

    Her team added individual enzymes into two biodegradable plastics, including polylactic acid, commonly used in food packaging. They inserted the enzymes along with another ingredient, a degradable additive Xu previously developed, which ensured the enzymes didn’t clump together and didn’t fall apart. The solitary enzymes grabbed the ends of the plastics’ molecular chains and ate as though they were slurping spaghetti, severing every chain link and preventing microplastic formation.

    Filaments of a new plastic material degrade completely (right) when submerged in tap water for several days.Adam Lau/Berkeley Engineering

    Adding enzymes usually makes plastic expensive and compromises its properties. However, Xu’s enzymes make up as little as 0.02 percent of the plastic’s weight, and her plastics are as strong and flexible as one typically used in grocery bags.

    The technology doesn’t work on all plastics because their molecular structures vary, a limitation Xu’s team is working to overcome. She’s filed a patent application for the technology, and a coauthor founded a startup to commercialize it. “We want this to be in every grocery store,” she says. More

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    A new book explores how military funding shaped the science of oceanography

    Science on a MissionNaomi OreskesUniv. of Chicago, $40

    In 2004, Japanese scientists captured the first underwater images of a live giant squid, a near-mythical, deep-ocean creature whose only interactions with humans had been via fishing nets or beaches where the animals lay dead or dying.

    Getting such a glimpse could have come much sooner. In 1965, marine scientist Frederick Aldrich had proposed studying these behemoths of the abyss using Alvin, a submersible funded by the U.S. Navy and operated by the Woods Hole Oceanographic Institution in Massachusetts. During the Cold War, however, studying sea life was not a top priority for the Navy, the main funder of U.S. marine research. Instead, the Navy urgently needed information about the terrain of its new theater of war and a thorough understanding of the medium through which submarines traveled.

    In Science on a Mission, science historian Naomi Oreskes explores how naval funding revolutionized our understanding of earth and ocean science — especially plate tectonics and deep ocean circulation. She also investigates the repercussions of the military’s influence on what we still don’t know about the ocean.

    The book begins just before World War II, when the influx of military dollars began. Oreskes describes how major science advances germinated and weaves those accounts with deeply researched stories of backstabbing colleagues, attempted coups at oceanographic institutions and daring deep-sea adventures. The story flows into the tumult of the 1970s, when naval funding began to dry up and scientists scrambled to find new backers. Oreskes ends with oceanography’s recent struggles to align its goals not with the military, but with climate science and marine biology.

    Each chapter could stand alone, but the book is best consumed as a web of stories about a group of people (mostly men, Oreskes notes), each of whom played a role in the history of oceanography. Oreskes uses these stories to explore the question of what difference it makes who pays for science. “Many scientists would say none at all,” she writes. She argues otherwise, demonstrating that naval backing led scientists to view the ocean as the Navy did — as a place where men, machines and sound travel. This perspective led oceanographers to ask questions in the context of what the Navy needed to know.

    One example Oreskes threads through the book is bathymetry. With the Navy’s support, scientists discovered seamounts and mapped mid-ocean ridges and trenches in detail. “The Navy did not care why there were ridges and escarpments; it simply needed to know, for navigational and other purposes, where they were,” she writes. But uncovering these features helped scientists move toward the idea that Earth’s outer layer is divided into discrete, moving tectonic plates (SN: 1/16/21, p. 16).

    Through the lens of naval necessity, scientists also learned that deep ocean waters move and mix. That was the only way to explain the thermocline, a zone of rapidly decreasing temperature that separates warm surface waters from the frigid deep ocean, which affected naval sonar. Scientists knew that acoustic transmissions depend on water density, which, in the ocean, depends on temperature and salinity. What scientists discovered was that density differences coupled with Earth’s rotation drive deep ocean currents that take cold water to warm climes and vice versa, which in turn create the thermocline.

    Unquestionably, naval funding illuminated physical aspects of the ocean. Yet many oceanographers failed to recognize that the ocean is also an “abode of life.” The Alvin’s inaugural years in the 1960s focused on salvage, acoustics research and other naval needs until other funding agencies stepped in. That switch facilitated startling discoveries of hydrothermal vents and gardens of life in the pitch black of the deep ocean.

    As dependence on the Navy lessened, many Cold War scientists and their trainees struggled to reorient their research. For instance, their view of the ocean, largely driven by acoustics and ignorant of how sound affects marine life, led to public backlash against studies that could harm sea creatures.

    “Every history of science is a history both of knowledge produced and of ignorance sustained,” Oreskes writes. “The impact of underwater sound on marine life,” she says, “was a domain of ignorance.”

    Buy Science on a Mission from Bookshop.org. Science News is a Bookshop.org affiliate and will earn a commission on purchases made from links in this article. More

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    Wildfires launch microbes into the air. How big of a health risk is that?

    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.

    [embedded content]
    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