Sunday, March 22, 2026

The freshwater hidden beneath the Great Salt Lake

In a first of its kind breakthrough, Utah geophysicists used electromagnetic data from airborne surveys to characterize a deep freshwater reservoir under Utah shrinking saline lake

University of Utah

helicopter AEM Antelope Island — image:
*A helicopter crew prepares to fly airborne electromagnetic survey equipment from a staging area on Antelope Island on Feb. 28, 2025.*
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Credit: Brian Maffly, University of Utah

A potentially huge underground reservoir of freshwater beneath the Great Salt Lake is coming into sharper focus with a new study that used airborne electromagnetic (AEM) surveys to X-ray geologic structures under Farmington Bay and Antelope Island off the lake’s southeastern shore.

An analysis of this data by University of Utah geophysicists shows that freshwater saturates the sediments beneath the lake’s hypersaline surface to depths of 3 to 4 kilometers, or about 10,000 to 13,000 feet. The helicopter-borne geophysical survey was conducted last year after Utah scientists documented freshwater welling up under pressure at several spots on the lake’s exposed playa in Farmington Bay, manifesting as strange phragmites-choked mounds.

The study demonstrated for the first time the ability of AEM methods to detect freshwater underneath thethin layer of conductive salt water at the surface of the Great Salt Lake, according to lead author Michael Zhdanov. His team also characterized the spatial extent of the freshwater reservoir beneath Farmington Bay and studied the potential depth of freshwater-saturated sediments by delineating the basement structure.

“We were able to answer the question of how deep is this potential reservoir, and what is its spatial extent beneath the eastern lake margin. If you know how deep, you know how wide, you know the porous space, you can calculate the potential freshwater volume,” said Zhdanov, a distinguished professor of geology & geophysics and director of the Consortium for Electromagnetic Modeling and Inversion, or CEMI.

A larger state-funded research effort focused on a newly discovered aquifer

The results appear in the Nature-affiliated journal Scientific Reports. This study is part of a larger research project led by the U’s Department of Geology & Geophysics and funded by the Utah Department of Natural Resources to understand the groundwater beneath Great Salt Lake, the largest terminal lake in the Western Hemisphere.

Overseen by some of the geology department’s most senior faculty and their graduate students, this effort has already resulted in two other important papers, with more to follow.

The evidence produced in this new study suggests that freshwater is entering the subsurface toward the lake’s interior, not its periphery as would be expected, according to hydrologist Bill Johnson, a co-author on all the Great Salt Lake groundwater papers.

“The unexpected part of this wasn't the salt lens that we see near the surface across the playa. It's that the freshwater underneath it extends so far in towards the interior of the lake and possibly under the entire lake. We don't know,” Johnson said on a recent appearance on KPCW’s Cool Science Radio show. “What we would normally expect as hydrologists is that that brine would occupy the entire volume underneath that lake. It's denser than the freshwater. You'd expect the freshwater from the mountains to come in somewhere at the periphery. But we find it's coming in towards the interior. And there's what appears to be deep volume of this freshwater coming in underneath that saline lens.”

A potential water source to mitigate dust pollution

These studies were triggered by the appearance in recent years of circular mounds, each 50 to 100 meters in diameter and covered with 15-foot-tall thickets of reeds, on the dried-out bed of Farmington Bay. The lake’s declining water levels have exposed 800 square miles of lake playa which is now becoming a major source of dust pollution blowing into Utah’s population centers.

Johnson, a professor of geology and geophysics, wants to explore whether the artesian groundwater could be safely tapped to mitigate the dust which contains toxic metals.

“There are beneficial effects of this groundwater that we need to understand before we go extracting more of it. A first-order objective is to understand whether we could use this freshwater to wet dust hotspots and douse them in a meaningful way without perturbing the freshwater system too much,” Johnson said. “To me, that's a primary objective because it's very practical and it's unlikely we'll be able to fill Farmington Bay and other parts of the playa enough to avoid some dust spots appearing at the higher elevations. This would be a great way to get at that.”

Johnson and his Utah colleagues, including Mike Thorne and Kip Solomon, are seeking funding to expand the groundwater studies to cover a much larger portion of the lake.

This latest paper measured electrical resistivity to a depth of about 100 meters via airborne electromagnetic surveys to discern freshwater from brine, which is far more electrically conductive. To see if this could be done, Johnson and Zhdanov hired a geophysical crew from Canada to fly electromagnetic equipment dangled under a helicopter in February 2025. The helicopter flew 10 east-west survey lines spanning Farmington Bay and across the northern portion of Antelope Island, for a total of 154 miles.

Looking under the playa

Zhdanov’s team analyzed the resulting data to create a map of the saline-freshwater interface. It showed how one phragmites mound sat above a spot where freshwater pushed through a gap in the impervious layer underlying the lake.

“Red means very conductive, blue is resistive,” Zhdanov said while explaining the map. “You clearly see near surface is saline water, 10 meters underneath is resistive freshwater. You see clearly it’s everywhere.”

Zhdanov’s research group CEMI has developed a technique to build 3D images of Earth’s subsurface by integrating electromagnetic data gathered aerially with magnetic measurements. Applied in this study, the researchers were able to create a tomographic image extending deep beneath Farmington Bay, providing critical insights into its geological and hydrological structure.

The results of the magnetic data inversion show that the basement under the Farmington Bay playa, is relatively shallow, less than 200 meters down, but then abruptly plunges to 3 to 4 kilometers. The drop-off, which occurs under the phragmites mound, represents a significant structural boundary that should be more fully explored.

“This is why we need to survey the entire Great Salt Lake. Then we’ll know the top and the bottom,” Zhdanov said. “To study the top we use airborne electromagnetic methods, which gives us the thickness of the saline layer and where the freshwater starts under the saline layer. To study the bottom, we use magnetic data. We use different techniques to study the vertical extent of this freshwater-saturated sediments, to find the depth to the basement.”

This pilot study covered just a sliver of the lake, but Zhdanov believes his team can fly airborne electromagnetic survey lines spanning the lake’s entire 1,500-square-mile footprint.

A lake-wide airborne survey could help guide regional water-resource planning and inform similar searches for freshwater under terminal lakes worldwide.

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The study was published in Scientific Reports under the title, “Airborne Geophysical Imaging of Freshwater Reservoir Beneath the Eastern Margin of Great Salt Lake.” Co-authors include Michael Jorgensen, Bill Johnson, and Kip Solomon of the U Department of Geology & Geophysics, and Leif Cox of TechnoImaging, a university spinoff founded by Michael Zhdanov in 2005. Funding came from Utah Department of Natural Resources, the Great Salt Lake Commissioners' Office, and the Consortium for Electromagnetic Modeling and Inversion (CEMI) at the University of Utah.

Map of the airborne electromagnetic survey area overlaid on the ESRI World Imagery basemap. Flight-

line locations are shown in red and cross Antelope Island and Farmington Bay. The circles indicate locations of phragmites mounds.

University of Utah

A helicopter lifts off from Antelope Island carrying electromagnetic survey equipment for a geophysical data-gathering mission over Farmington Bay in February 2025.

Credit

Brian Maffly, University of Utah

JournaL

Scientific Reports

DOI

10.1038/s41598-026-40995-5

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Airborne Geophysical Imaging of Freshwater Reservoir Beneath the Eastern Margin of Great Salt Lake

Old-growth forests store a lot more carbon than managed forests

Lund University

Swedish old-growth forests store 83 percent more carbon than managed forests, according to a new study from Lund University. The difference is substantially larger than previous estimates and is mainly due to large carbon stocks in the soil.

VIDEO STORY: https://www.youtube.com/watch?v=8HtSXBUDSTw

The study, published in the scientific journal Science, is the most comprehensive mapping of how much carbon is stored in Swedish old-growth forests to date. The results show that old-growth forests store 78–89 per cent more carbon than managed forests in living trees, dead wood, and in the soil down to a depth of 60 centimetres.

“The most surprising result is the large amounts of carbon stored in the soil of old-growth forests. It is the same amount as all the carbon in managed forests - trees, dead wood, and soil, combined,” says Anders Ahlström, researcher at the Department of Environmental and Earth Sciences at Lund University.

The work behind the study took nearly ten years. Because there was no national map of old-growth forests, the researchers first had to identify and map forests that had been very little affected, or not affected at all, by direct human activity. Extensive fieldwork was then carried out across the country, including nearly 220 soil pits dug to a depth of one meter to measure carbon storage in the soil.

The total difference in carbon storage between old-growth forests and managed forests -including carbon stored in wood products - is about 3 to 8 times greater than previous estimates. This difference corresponds to approximately 211 years of Sweden’s current fossil carbon dioxide emissions, or about 1.5 times all fossil emissions since 1834.

“Carbon stored in wood products from harvested forests is relatively small and does not even compensate for the difference in dead wood, let alone the differences in living trees and soil. This is because most products are short-lived, such as paper and bioenergy, where the carbon quickly returns to the atmosphere,” says Didac Pascual, researcher at the Department of Environmental and Earth Sciences.

Old-growth forests serve as a reference for what Swedish forests would look like without forest management and land use. The difference in carbon storage between old-growth forests and today’s managed forests reflects the combined effect of direct human land use, all carbon gains and losses—primarily since the late 1800s, and especially since the 1950s when today’s large-scale forest management was established.

“Comparing carbon storage in old-growth and managed forests is crucial, because contemporary measurements of carbon uptake can miss large historical carbon losses. Carbon storage shows the full picture over time. Old-growth forests serve as a reference for understanding how forest management affects ecosystems and the carbon balance,” says Anders Ahlström.

The results are relevant to discussions about the role of forests in the climate transition. The large differences in carbon storage implies that converting natural forests into managed forests leads to much greater losses of carbon or potential carbon uptake than previously estimated. This affects calculations of the climate benefits of forest products such as bioenergy and building materials.

“Converting old-growth forests reduces the landscape’s carbon storage more than previously believed. Protecting remaining old-growth forests and allowing unmanaged forests to recover could provide substantially greater climate benefits than earlier studies have shown. A large portion of the clear-cutting that occurs each year takes place in old-growth forests,” concludes Didac Pascual.

Journal

Science

DOI

10.1126/science.adz8554

Article Title

Higher carbon storage in primary than secondary boreal forests in Sweden

Article Publication Date

19-Mar-2026

Aquatic plant reduces antibiotics in water and genetic damage in fish

A study conducted in the Piracicaba River in the state of São Paulo, Brazil, shows that the macrophyte Salvinia auriculata can act as a sink for these contaminants, reducing bioaccumulation and genotoxicity.

Fundação de Amparo à Pesquisa do Estado de São Paulo

Aquatic plant reduces antibiotics in water and genetic damage in fish — image:
X-ray of a lambari fish contaminated with carbon-14-radiolabeled enrofloxacin. The color indicates the radiative intensity of the signal, ranging from low (blue) to high (red)
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Credit: Patrícia Alexandre Evangelista

A study conducted by researchers at the Center for Nuclear Energy in Agriculture at the University of São Paulo (CENA-USP) and published in the journal Environmental Sciences Europe identified residues of different classes of antibiotics in the Piracicaba River, one of the main waterways in the interior of the state of São Paulo, Brazil. The study also assessed how these substances accumulate in fish and how an aquatic plant widely found in the region, Salvinia auriculata, can partially mitigate this accumulation.

Led by Patrícia Alexandre Evangelista and supported by FAPESP, the study combined environmental monitoring, bioaccumulation studies, genetic damage analyses in aquatic organisms, and phytoremediation experiments. This integrated approach enabled the researchers not only to map contamination but also discuss ecological risks and potential strategies for addressing a problem associated with both human and veterinary use of medications.

Samples were collected in the region of the Santa Maria da Serra dam, near the Barra Bonita reservoir, where pollutants from the entire Piracicaba River basin accumulate. This area receives contributions from treated urban sewage, domestic effluents, and activities associated with aquaculture and pig farming, as well as diffuse runoff from agriculture.

Water, sediment, and fish samples were analyzed during two periods: the rainy season and the dry season. In total, the monitoring included 12 antibiotics from widely used classes – tetracyclines, fluoroquinolones, sulfonamides, and phenols. “The results showed a clear pattern of seasonality. During the rainy season, most antibiotics had concentrations below detection limits. In the dry season, however, when water volume decreases and contaminants become concentrated, different compounds were detected,” says Evangelista.

Concentrations ranged from nanograms per liter in the water to micrograms per kilogram in the sediment. For example, fluoroquinolones such as enrofloxacin and sulfonamides were detected in the sediment at levels higher than those reported in comparable international studies. The sediment is rich in organic matter and nutrients, such as phosphorus, calcium, and magnesium. This composition allows the sediment to act as a reservoir for these compounds, with the potential for remobilization over time.

“One of the most significant findings of the study was the detection of chloramphenicol in lambari fish (Astyanax sp.) collected from local fishermen in the Barra Bonita region. Chloramphenicol is an antibiotic whose use in livestock is prohibited in Brazil precisely because of the risks associated with its toxicity,” the researcher states.

The substance was found in the fish only during the dry season, with concentrations in the range of tens of micrograms per kilogram. This is noteworthy because the fish species is widely sold and consumed locally, indicating a possible indirect route of human exposure through food.

Evangelista explains that the choice of chloramphenicol and enrofloxacin as the focus of the laboratory experiments was due to their environmental and health relevance. “Enrofloxacin is widely used in animal husbandry, including aquaculture, as well as in human medicine. Chloramphenicol, on the other hand, is still used in humans despite being banned for food-producing animals and serves as a historical marker of persistent contamination,” she explains.

In addition to mapping contamination, the study investigated whether Salvinia auriculata, a floating macrophyte often considered a water body pest, could help remove antibiotics from the environment.

In laboratory experiments, the plant was exposed to environmental and 100-times-higher concentrations of enrofloxacin and chloramphenicol using carbon-14-radiolabeled compounds. Using radiolabeled molecules allowed for precise tracking of the fate of the antibiotics in the water, plant, and fish.

“The results showed the high efficiency of Salvinia in removing enrofloxacin. In treatments with higher plant biomass, more than 95% of the antibiotic was removed from the water within a few days. The half-life of the compound dropped to about two to three days. In the case of chloramphenicol, removal was slower and partial. The plant was able to remove 30% to 45% of the antibiotic from the water, with half-lives ranging from 16 to 20 days, indicating the greater persistence of the compound in the environment,” the researcher reports.

Autoradiography images revealed that in both cases, the antibiotics were concentrated primarily in the roots of the plant, suggesting that rhizofiltration and root absorption play a central role in the process.

One of the most complex aspects of the study concerns bioaccumulation in fish. Controlled experiments showed that reducing the antibiotic concentration in the water does not necessarily result in lower absorption by the organism.

For enrofloxacin, most of the compound remained dissolved in the water and was quickly eliminated by the lambari, with a half-life of about 21 days. The bioconcentration factor was low, indicating a lower tendency for accumulation in tissues. Chloramphenicol, on the other hand, exhibited different behavior. This antibiotic showed greater persistence in the organism, with a half-life exceeding 90 days and a high bioconcentration factor reflecting greater retention in fish tissues.

The presence of Salvinia auriculata altered this dynamic. While the plant significantly reduced the amount of antibiotic in the water, there was sometimes an increase in the absorption rate by the fish. One hypothesis is that the plant may partially transform the original compound, making it more bioavailable even at lower total concentrations.

“This shows that using plants as ‘sponges’ for contaminants is not a trivial matter. The presence of the macrophyte changes the entire system, including the way the organism comes into contact with the contaminant,” Evangelista notes.

Despite these complexities, significant results emerged from the genotoxic analyses. Chloramphenicol significantly increased DNA damage in the fish, as measured by the frequency of micronuclei and nuclear abnormalities in blood cells. When Salvinia auriculata was present in the system, however, this damage was reduced, approaching the levels observed in the control groups. For enrofloxacin, however, the presence of the plant did not lead to a significant reduction in genotoxic effects.

“The interpretation we propose is that, in the case of chloramphenicol, the plant may generate fewer genotoxic byproducts or release antioxidant compounds into the rhizosphere, reducing oxidative stress in the fish. On the other hand, enrofloxacin is chemically more stable and may produce persistent and potentially toxic metabolites whose action is not neutralized by the macrophyte,” the researcher comments.

Evangelista emphasizes that Salvinia auriculata should not be viewed as a simple or definitive solution to antibiotic pollution. The study highlights its potential and limitations. In addition to uncertainties regarding byproduct formation, there is the challenge of managing contaminated biomass. If not properly removed and treated, the plant can become a secondary source of pollution by reintroducing antibiotics into the environment.

Nevertheless, the results suggest that aquatic macrophytes could be incorporated into cost-effective, nature-based mitigation strategies, particularly in systems where advanced treatment technologies, such as ozonation or oxidative processes, are economically infeasible.

“The study shows that the problem is real, measurable, and complex. And any strategy to address it must consider not only the removal of the contaminant, but also its biological and ecological effects,” the researcher concludes.

“The detection of antibiotic residues in the water, sediments, and fish of the Piracicaba River shows just how harmful human activities can be. The resistance of microorganisms to antibiotics can lead to the emergence of superbugs in the environment. The research yielded positive results with low-cost environmental solutions and enabled a better understanding of the integrated functioning of aquatic ecosystems and the use of effective natural techniques for impact mitigation,” adds Valdemar Luiz Tornisielo, supervisor of Evangelista’s research and co-author of the article.

The radiolabeled molecules used in the study were provided by the International Atomic Energy Agency (IAEA).

About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

Journal

Environmental Sciences Europe

DOI

10.1186/s12302-025-01275-7

Article Title

Integrated approach for assessing and mitigating antibiotic contamination in natural waters using bioaccumulation and phytoremediation

Long-term road surveys reveal widespread declines in South African birds of prey

University of Cape Town - Faculty of Science

Secretarybird by Megan Murgatroyd — image:
A new study has revealed widespread declines of many birds of prey across South Africa, including species such as this secretarybird, which showed declines of 68% over 16 years
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Credit: Photo by Megan Murgatroyd

A comprehensive study has revealed substantial declines in many of South Africa’s birds of prey (raptors) over the past 16 years, raising fresh concerns about the conservation status of several iconic and threatened species. Researchers assessed population trends for 18 raptor and 8 large terrestrial bird species across central South Africa between 2009 and 2025. Half of the species experienced significant declines, many exceeding 50%, while only three showed clear increases.

“These results point to widespread and often severe population declines across South Africa’s raptor community,” said Dr Santiago Zuluaga, lead author of the study and a researcher at the University of Cape Town and National Museum of Natural Sciences of Spain. “What is particularly concerning is that some of the steepest declines were detected in species that play key ecological roles and are already considered conservation priorities.”

DECLINES IN THREATENED AND ICONIC RAPTORS
Several globally threatened raptors showed steep declines, including the Endangered Secretarybird, which dropped 68% over 16 years. “The declines detected in species such as Secretarybirds are especially worrying,” said Dr Megan Murgatroyd, International Programs Director at HawkWatch International and a co-author on the study. “These birds require vast areas to survive and reproduce, so sustained population losses at this scale suggest that pressures across the landscape are having real and lasting impacts.”

The study also found strong declines in migratory raptors such as Lesser Kestrel, Amur Falcon, and Steppe Buzzard, highlighting the vulnerability of species dependent on multiple regions. Sharp declines were also detected in species currently listed as Least Concern, including Spotted Eagle-Owl and Jackal Buzzard, suggesting population changes may occur before they are reflected in formal conservation assessments.

THE VALUE OF LONG-TERM MONITORING
The road count data underpinning the study were collected over more than 15 years, largely through repeated surveys conducted across central South Africa.

“When I started these road counts over 15 years ago, I never expected that they would reveal such severe declines across so many species,” said Ronelle Visagie of the Endangered Wildlife Trust, who carried out the fieldwork. “It involved a huge amount of time on the road, counting birds year after year, but it is reassuring to see that all that effort has produced something meaningful that can genuinely inform conservation.”

STRENGTHENING THE EVIDENCE BASE FOR CONSERVATION
To place these findings in a broader context, researchers compared their road-survey results with trends from the Southern African Bird Atlas Project (SABAP2), a key citizen-science initiative. While atlas data remain invaluable for mapping species distributions and supporting biodiversity monitoring, the comparison showed that different survey approaches can sometimes produce contrasting signals of population change. “Citizen science atlas projects like SABAP2 are absolutely vital for bird conservation in Africa,” said Associate Professor Arjun Amar, senior author of the study from the University of Cape Town. “Our findings underline the importance of combining multiple monitoring approaches, particularly for wide-ranging species such as raptors, to ensure we have the most accurate picture possible of how populations are changing.”

WHY IT MATTERS
Raptors are vital as top predators and scavengers, indicators of environmental health, yet across Africa they are among the fastest-declining bird groups, pressured by land-use change, infrastructure, illegal killing, and climate change. “With human populations in Africa projected to increase sharply over the coming decades, pressures on biodiversity are only likely to intensify,” said Zuluaga. “Robust, long-term monitoring is essential if we are to detect declines early and implement conservation actions before populations reach critical levels.

Journal

Biological Conservation

DOI

10.1016/j.biocon.2026.111764