Tag: nature

Scientists stunned by salt giants forming beneath the Dead Sea

Source:University of California – Santa Barbara

Summary:The Dead Sea isn’t just the saltiest body of water on Earth—it’s a living laboratory for the formation of giant underground salt deposits. Researchers are unraveling how evaporation, temperature shifts, and unusual mixing patterns lead to phenomena like “salt snow,” which falls in summer as well as winter. These processes mirror what happened millions of years ago in the Mediterranean, leaving behind thick salt layers still buried today.Share:

    

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Salt Giants Rising Beneath the Dead Sea
The Dead Sea’s extreme salinity and shifting water layers produce salt giants and even summer “salt snow.” Studying these rare processes provides clues to ancient oceans and modern coastal stability. Credit: Shutterstock

The Dead Sea is a confluence of extraordinary conditions: the lowest point on the Earth’s surface, with one of the world’s highest salinities. The high concentration of salt gives it a correspondingly high density, and the water body’s status as the deepest hypersaline lake gives rise to interesting and often temperature-related phenomena below the water’s surface that researchers are still uncovering.

One of the most intriguing features of the Dead Sea continues to be revealed: salt giants, large-scale salt deposits.

“These large deposits in the Earth’s crust can be many, many kilometers horizontally, and they can be more than a kilometer thick in the vertical direction,” said UC Santa Barbara mechanical engineering professor Eckart Meiburg, lead author of a paper published in the Annual Review of Fluid Mechanics. “How were they generated? The Dead Sea is really the only place in the world where we can study the mechanism of these things today.”

Indeed, while there are other bodies of water in the world with massive salt formations, such as the Mediterranean and Red seas, only in the Dead Sea can one find them in the making, which allows researchers to tackle the physical processes behind their evolution, and in particular, the spatial and temporal variations in their thickness.

Evaporation, precipitation, saturation

In their paper, Meiburg and fellow author Nadav Lensky of the Geological Survey of Israel cover the fluid dynamical and associated sediment transport processes currently governing the Dead Sea. These processes are influenced by several factors, including the Dead Sea’s status as a saltwater terminal lake — a lake with no outflow — leaving evaporation as the primary way water leaves the lake, which has been shrinking for millennia and leaving salt deposits as it does so. More recently, damming of the Jordan River, which feeds into the lake, has accelerated lake level decline, estimated at roughly 1 meter (3 feet) per year.

Temperatures along the water column also play a role in the dynamics behind salt giants and other formations such as salt domes and chimneys. A once “meromictic” (stably stratified) lake — the Dead Sea was layered such that less dense warmer water at the surface overlaid a more saline, cooler layer at depth throughout the entire year.

“It used to be such that even in the winter when things cooled off, the top layer was still less dense than the bottom layer,” Meiburg explained. “And so as a result, there was a stratification in the salt.”

That changed in the early 1980s thanks to the partial diversion of the Jordan River, which resulted in evaporation outpacing the rate of freshwater inflow. At that time, the surface salinity reached the levels found at depth, enabling mixing between the two layers and transitioning the lake from meromictic to holomictic (a lake that experiences annual overturns in the water column). The Dead Sea continues to stratify, but only for eight of the warmer months of the year.

In 2019, Meiburg et al identified a rather unique process occurring in the lake during the summer: halite crystal precipitation or “snow” that was more typical in the cooler season. Halite (“rock salt”) precipitates when the concentration of salt exceeds the amount that the water can dissolve, hence the deeper, colder, denser conditions of the bottom layer are where it is most likely to happen, and in the cooler months. However, they observed that during the summer, while evaporation was increasing the salinity of the upper layer, salts were nonetheless continuing to dissolve in that layer due to its warmer temperature. This leads to a condition called “double diffusion” at the interface between the two layers, in which sections of the saltier warmer water of the top layer cool down and sink, while portions of the lower, cooler, relatively less dense water warm up and rise. As the upper, denser layer cools down, salts precipitate out, creating the “salt snow” effect.

The combination of evaporation, temperature fluctuations and density changes throughout the water column, in addition to other factors including internal currents and surface waves, conspire to create salt deposits of various shapes and sizes, assert the authors. In contrast to shallower hypersaline bodies in which precipitation and deposition occur during the dry season, in the Dead Sea, these processes were found to be most intense during the winter months. This year-round “snow” season at depth explains the emergence of the salt giants, found in other saline bodies such as the Mediterranean Sea, which once dried up during the Messinian Salinity Crisis, about 5.96 to 5.33 million years ago.

“There was always some inflow from the North Atlantic into the Mediterranean through the Strait of Gibraltar,” Meiburg said. “But when tectonic motion closed off the Strait of Gibraltar, there couldn’t be any water inflow from the North Atlantic.” The sea level dropped 3-5 km (2-3 miles) due to evaporation, creating the same conditions currently found in the Dead Sea and leaving behind the thickest of this salt crust that can still be found buried below the deep sections of the Mediterranean, he explained. “But then a few million years later the Strait of Gibraltar opened up again, and so you had inflow coming in from the North Atlantic and the Mediterranean filled up again.”

Meanwhile, salinity fluxes and the presence of springs on the sea floor contribute to the formation of other interesting salt structures, such as salt domes and salt chimneys, according to the researchers.

In addition to gaining a fundamental understanding of some of the idiosyncratic processes that can occur in evaporating, hypersaline lakes, research into the associated sediment transport processes occurring on the emerging beaches may also yield insight on the stability and erosion of arid coastlines under sea level change, as well as the potential for resource extraction, the authors state.

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https://www.sciencedaily.com/releases/2025/09/250916221828.htm

Hungry flathead catfish are changing everything in the Susquehanna

New study suggests that smallmouth bass and channel catfish are changing what they eat to avoid having to compete with or being eaten by the invader.

Source:Penn State

Summary: Flathead catfish are rapidly reshaping the Susquehanna River’s ecosystem. Once introduced, these voracious predators climbed to the top of the food chain, forcing native fish like channel catfish and bass to shift diets and habitats. Using stable isotope analysis, researchers uncovered how the invaders disrupt food webs, broaden dietary overlaps, and destabilize energy flow across the river system. The findings show how a single invasive species can spark cascading ecological consequences. Share:

    

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Flathead Catfish Take Over the Susquehanna
Flatheads grow fast in this river system, attain large body sizes and can eat a variety of prey. Because adult flatheads have few natural predators, they can exert strong control over the ecosystem. Credit: Penn State

Flathead catfish, opportunistic predators native to the Mississippi River basin, have the potential to decimate native and recreational fisheries, disrupting ecosystems in rivers where they become established after their introduction or invasion from a nearby river drainage. That concern led a team of researchers from Penn State, the U.S. Geological Survey (USGS), and the Pennsylvania Fish and Boat Commission to assess how flatheads are affecting the food web and energy flow in the Susquehanna River in Pennsylvania, where they were first detected in 1991. Their population has grown rapidly in the decades since.

“Flatheads grow fast in this river system, attain large body sizes and can eat a variety of prey,” said study first author Olivia Hodgson, a master’s degree student in Penn State’s Intercollege Graduate Degree Program in Ecology. “Because adult flatheads have few natural predators, flathead catfish can exert strong control over the ecosystem.”

Hodgson is working with Tyler Wagner, a scientist with the USGS Pennsylvania Cooperative Fish and Wildlife Research Unit Program and a Penn State affiliate professor of fisheries ecology. He is senior author on the study. In findings published Sept. 4 in Ecology, the researchers reported that flathead catfish are apex predators.

Flatheads had the highest trophic position — the level an organism occupies in a food web, based on its feeding relationships — even higher than resident top predators such as smallmouth bass and channel catfish. Channel catfish had a lower trophic position in areas with flathead catfish. This means they now eat lower on the food chain, likely because they are being outcompeted by flatheads or avoiding them, the researchers explained. In areas with flathead catfish, they found, all species showed broader and overlapping diets.

“This suggests that resident species are changing what they eat to avoid competing with or being eaten by the invader,” Hodgson said. “These findings support the ‘trophic disruption hypothesis,’ that says when a new predator enters an ecosystem, it forces existing species to alter their behavior, diets and roles in the food web. This can destabilize ecosystems over time. Our study highlights how an invasive species can do more than just reduce native populations — it can reshape entire foodwebs and change how energy moves through ecosystems.”

Although the predatory effects of invasive catfishes on native fish communities have been documented — such as in a recent study on the Susquehanna River led by researchers at Penn State — the impacts of invasion on riverine food webs are poorly understood, Hodgson noted. This study quantified the effects of invasive flathead catfish on the food web in the Susquehanna by comparing uninvaded river sections to invaded sections, focusing on several key species: flathead catfish — invader, channel catfish and smallmouth bass — resident predators, and crayfish and minnows — prey.

In addition to evaluating trophic position, the researchers analyzed the isotopic niche occupied by the fish species — the range of carbon and nitrogen markers found within the tissues of an organism, reflecting its diet and habitat, providing insights into its ecological role.

To reach their conclusions, the researchers employed stable isotope analysis, a widely used tool that can explain patterns within a food web, highlighting links between trophic positions, as well as the breadth and overlap of trophic niches. Stable isotope analysis is especially useful for studying invasion ecology, such as investigating trophic reorganization and trophic overlap between introduced and resident species.

When fish eat, their bodies incorporate the isotopic signature of their food. By sampling their tissues, scientists can measure nitrogen isotopes and determine their diet, carbon isotopes to determine habitat use, and compare isotopic signatures across regions to deduce fish migration or habitat shifts. For this study, channel catfish, smallmouth bass, minnows and crayfish were selected as focal species because a previous diet analysis conducted in collaboration with Penn State, USGS, and Pennsylvania Fish and Boat Commission researchers within the Susquehanna River, showed that these species are important prey for flathead catfish.

The researchers collected a total of 279 fish and 64 crayfish for stable isotope analysis, including 79 flathead catfish, 45 smallmouth bass, 113 channel catfish and 42 minnows comprising nine species. All samples were oven dried and ground to a fine powder using a mortar and pestle. Stable isotope samples were sent to Penn State’s Core Facilities and the Michigan State University Stable Isotope Laboratories for isotope determination.

“Stable isotope analysis explained patterns within the Susquehanna food web in habitats invaded and not invaded by the flathead catfish, and it allowed us to understand links between different species in the river food web and how invasive species might lead to changes in how native species interact and compete, what they eat and how their diets overlap, and if they might be displaced from preferred habitats by the invader,” Hodgson said. “We were able to infer resource use, helping us to better understand potential competition for resources and how this changes when flathead catfish become established.”

Contributing to the research were: Sydney Stark, recent Penn State graduate with a master’s degree in wildlife and fisheries science; Megan Schall, associate professor of biology and science at Penn State Hazleton; Geoffrey Smith, Susquehanna River biologist for the Pennsylvania Fish and Boat Commission; and Kelly Smalling, research hydrologist withtheU.S. Geological Survey, New Jersey Water Science Center.

Funding for this research was provided by Pennsylvania Sea Grant and the U.S. Geological Survey.

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https://www.sciencedaily.com/releases/2025/09/250909031516.htm

Oceans could reach a dangerous tipping point by 2050

Source:University of California – Santa Barbara

Summary:UC Santa Barbara researchers project that human impacts on oceans will double by 2050, with warming seas and fisheries collapse leading the charge. The tropics and poles face the fastest changes, and coastal regions will be hardest hit, threatening food and livelihoods worldwide.Share:

    

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Oceans Near Breaking Point by 2050
By 2050, ocean impacts from climate change and overuse could double—unless urgent action is taken. Credit: Shutterstock

The seas have long sustained human life, but a new UC Santa Barbara study shows that rising climate and human pressures are pushing the oceans toward a dangerous threshold.

Vast and powerful, the oceans can seem limitless in their abundance and impervious to disturbances. For millennia, humans have supported their lives, livelihoods and lifestyles with the ocean, relying on its diverse ecosystems for food and material, but also for recreation, business, wellness and tourism.

Yet the future of our oceans is worrying, according to researchers at UCSB’s National Center for Ecological Analysis and Synthesis (NCEAS).

“Our cumulative impact on the oceans, which is already substantial, is going to double by 2050 — in just 25 years,” said marine ecologist and NCEAS director Ben Halpern, who led the effort to forecast the future state of marine environments as they bow under the combined pressures of human activities, which include ocean warming, fisheries biomass loss, sea level rise, acidification and nutrient pollution, among other impacts. “It’s sobering. And it’s unexpected, not because impacts will be increasing — that is not surprising — but because they will be increasing so much, so fast.”

The research team, which includes collaborators from Nelson Mandela University in South Africa, also finds that the tropics and the poles will experience the fastest changes in impacts, and that coastal areas will feel the brunt of the increased impacts.

Their research, supported in large part by the National Science Foundation, is published in the journal Science.

A comprehensive global model of human impacts

As human activity on the ocean and along the coast has intensified, so have impacts on the marine environment. Halpern and a group of scientists first tackled the challenge of understanding how these pieces fit together to affect the ocean nearly 20 years ago, laying the groundwork for the current study.

“People tracked one issue at a time, but not everything together,” Halpern said. “More importantly, there was a pervasive sense that the ocean is so huge the human impacts couldn’t possibly be that bad.”

Their quest to build a comprehensive model of human impacts on the ocean led to a 2008 paper in the journal Science, a landmark study that synthesized 17 global data sets to map the intensity and extent of human activity on the world’s oceans. That initial view revealed startling results: No place was untouched, and 41% of the world’s marine environments were heavily impacted.

“The previous paper tells us where we are; the current paper tells us where we are headed,” Halpern said.

Ocean warming and biomass loss due to fisheries are expected to be the largest overall contributors to future cumulative impacts. Meanwhile, the tropics face rapidly increasing rates of impact, while the poles, which already experience a high level of impact, are expected to experience even more. According to the paper, the high level of future impacts “may exceed the capacity of ecosystems to cope with environmental change,” in turn posing challenges for human societies and institutions in a variety of ways.”

The world’s coasts are expected to bear the brunt of these increasing cumulative impacts — an unsurprising reality, the researchers say, given most human uses of the ocean are near coasts. Yet it’s also a “worrisome result nonetheless,” according to the paper, because the coasts “are where people derive most value from the ocean.” Additionally, many countries are dependent on the ocean for food, livelihood and other benefits. “Many of these countries will face substantial increases,” Halpern said.

The authors contend that enacting policies to reduce climate change and to strengthen fisheries management could be effective ways to manage and reduce human impacts, given the outsize roles that ocean warming and biomass loss play in the estimate of future human impacts on the ocean. Likewise, prioritizing management of habitats that are expected to be heavily impacted — such as salt marshes and mangroves — could help reduce the pressures on them.

In presenting these forecasts and analyses, the researchers hope that effective action can be taken sooner rather than later to minimize or mitigate the effects of increased pressures from human activity.

“Being able to look into the future is a super powerful planning tool,” Halpern said. “We can still alter that future; this paper is a warning, not a prescription.”

Research in this paper was also conducted by Melanie Frazier and Casey C. O’Hara at UCSB, and Alejandra Vargas-Fonseca and Amanda T. Lombard at Nelson Mandela University in South Africa.

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https://www.sciencedaily.com/releases/2025/09/250905180728.htm

Even the toughest corals are shrinking in warming seas

Resilient coral growth predicted to decrease over next 3 decades, study finds.

Source:Ohio State University

Summary:Scientists found that Red Sea corals can endure warming seas but grow much smaller and weaken under long-term heat stress. Though recovery is possible in cooler months, rising global temperatures may outpace their resilience, endangering reefs and the people who depend on them.Share:

    

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Even the Toughest Corals Are Shrinking
Resilient Red Sea corals survive extreme heat but shrink and weaken, raising alarms about the future of marine life and reef-dependent communities. Credit: Shutterstock

As coral reefs decline at unprecedented rates, new research has revealed that some coral species may be more resilient to warming temperatures than others.

By studying how six months of elevated ocean temperatures would affect a species of coral from the northern Red Sea called Stylophora pistillata, scientists found that although these organisms can certainly survive in conditions that mimic future warming trends, they don’t thrive.

Stylophora pistillata tend to be tolerant of high ocean temperatures, but when continuously exposed to temperatures of 27.5 and 30 degrees Celsius (81.5 and 86 degrees Fahrenheit) — baseline warming expected in tropical oceans by 2050 and 2100 — scientists saw various changes in coral growth, metabolic rates, and even energy reserves. For instance, coral in 27.5 degrees Celsius waters survived, but were 30% smaller than their control group; those placed in 30 degrees Celsius waters wound up being 70% smaller.

“In theory, if corals in the wild at these temperatures are smaller, reefs might not be as diverse and may not be able to support as much marine life,” said Ann Marie Hulver, lead author of the study and a former graduate student and postdoctoral scholar in earth sciences at The Ohio State University. “This could have adverse effects on people that depend on the reef for tourism, fishing or food.”

Overall, the team’s results suggest that even the most thermally tolerant coral species may suffer in their inability to overcome the consequences of warming seas.

The study was published on September 3 in the journal Science of the Total Environment.

While current predictions for coral reefs are dire, there is some good news. During the first 11 weeks of the experiment, researchers saw that corals were only minimally affected by elevated baseline temperatures. Instead, it was the cumulative impact of chronic high temperatures that compromised coral growth and caused them to experience a higher metabolic demand.

The coral later recovered after being exposed for a month to 25 degree Celsius waters, but had a dark pigmentation compared to corals that were never heated. This discovery implies that despite facing ever longer periods of threat from high ocean temperatures in the summer months, resilient coral like S. pistillata can bounce back when waters cool in the winter, researchers say.

Still, as ocean temperatures are expected to increase by 3 degrees Celsius by 2100, expecting coral reefs to predictably bend to projected climate models can be difficult, according to the researchers.

This team’s research does paint a more detailed picture of how coral reefs may look and function in the next 50 years, said Andrea Grottoli, co-author of the study and a professor in earth sciences at Ohio State.

“Survival is certainly the No. 1 important thing for coral, but when they’re physiologically compromised, they can’t do that forever,” said Grottoli. “So there’s a limit to how long these resilient corals can cope with an ever increasing warming ocean.”

Gaining a more complex understanding of how warming waters can alter coral growth and feeding patterns may also better inform long-term conservation efforts, said Grottoli.

“Conservation efforts could focus on areas where resilient coral are present and create protected sanctuaries so that there are some ecosystems that grow as high-probability-success reefs for the future,” she said.

For now, all coral reefs are still in desperate need of protection, researchers note. To that end, Hulver imagines future work could be aimed at investigating the resilience of similar species of coral, including replicating this experiment to determine if sustained warming might cause trade-offs in other biological processes, such as reproduction.

“For coral, six months is still a very small snapshot of their lives,” said Hulver. “We’ll have to keep on studying them.”

Other Ohio state co-authors include Shannon Dixon and Agustí Muñoz-Garcia as well as Éric Béraud and Christine Ferrier-Pagès from the Centre Scientifique de Monaco, and Aurélie Moya, Rachel Alderdice and Christian R Voolstra from the University of Konstanz. The study was supported by the National Science Foundation and the German Research Foundation.

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https://www.sciencedaily.com/releases/2025/09/250905112308.htm

Geologists got it wrong: Rivers didn’t need plants to meander

Source:Stanford University

Summary:Stanford researchers reveal meandering rivers existed long before plants, overturning textbook geology. Their findings suggest carbon-rich floodplains shaped climate for billions of years.Share:

    

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Geologists Were Wrong About Meandering Rivers
A view of seasonal flow in Shoshone Creek – an unvegetated meandering stream in Nevada. Credit: M. Hasson and M. Lapôtre

A new Stanford study challenges the decades-old view that the rise of land plants half a billion years ago dramatically changed the shapes of rivers.

Rivers generally come in two styles: braided, where multiple channels flow around sandy bars, and meandering, where a single channel cuts S-curves across a landscape. Geologists have long thought that before vegetation, rivers predominantly ran in braided patterns, only forming meandering shapes after plant life took root and stabilized riverbanks.

The new study, which was published online by the journal Science on Aug. 21, 2025, suggests the theory that braided rivers dominated the first 4 billion years of Earth’s history is based on a misinterpretation of the geological record. The research demonstrates that unvegetated meandering rivers can leave sedimentary deposits that look deceptively similar to those of braided rivers. This distinction is crucial for our understanding of Earth’s early ecology and climate, as a river’s type determines how long sediment, carbon, and nutrients are stored in floodplains.

“With our study, we’re pushing back on the widely accepted story of what landscapes looked like when plant life first evolved on land,” said lead author Michael Hasson, a PhD student in Mathieu Lapôtre’s lab at the Stanford Doerr School of Sustainability. “We’re rewriting the story of the intertwined relationship between plants and rivers, which is a significant revision to our understanding of the history of the Earth.”

The muddy floodplains of meandering rivers – dynamic ecosystems created over thousands of years by river overflow – are among the planet’s most abundant non-marine carbon reservoirs. Carbon levels in the atmosphere, in the form of carbon dioxide, act as Earth’s thermostat, regulating temperature over vast timescales. Accurately budgeting for the carbon caches created by meandering rivers could help scientists build more comprehensive models of Earth’s ancient and future climate.

“Floodplains play an important role in determining how, when, and whether carbon is buried or released back into the atmosphere,” Hasson said. “Based on this work, we argue carbon storage in floodplains would have been common for much longer than the classic paradigm that assumes meandering rivers only occurred over the last several hundred million years.”

Where the river flows

To gauge vegetation’s impact on river channel patterns, the researchers examined satellite imagery of about 4,500 bends in 49 current-day meandering rivers. About half of the rivers were unvegetated and half were densely or partly vegetated.

The researchers keyed in on point bars – the sandy landforms that develop on the inside bends of meandering rivers as water flow deposits sediments. Unlike the sandy bars that form in the middle of braided rivers, point bars tend to migrate laterally away from the centers of rivers. Over time, this migration contributes to meandering rivers’ characteristically sinuous channel shapes.

Recognizing that these sandy bars form in different places based on river style, geologists for decades have measured the trajectory of bars in the rock record to reveal ancient river paths. The rocks, typically of sandstones and mudstones, provide evidence for divergent river styles because each deposits different kinds of and amounts of rock-forming sediment, giving geologists clues for reconstructing long-ago river geometries. If sandstones showed little variation in the angle of bar migration, geologists interpreted the bars as moving downstream, and thus that a braided river created the deposits.

Using this technique, geologists had noticed that rivers changed the way they behaved around the time that plants first evolved on Earth. This observation led to the conclusion that land plants made river meandering possible, for instance by trapping sediment and stabilizing riverbanks.

“In our paper, we show that this conclusion – which is taught in all geology curricula to this day – is most likely incorrect,” said Lapôtre, the paper’s senior author and an assistant professor of earth and planetary sciences at the Doerr School of Sustainability.

By looking at modern rivers with a wide range of vegetation cover, the researchers showed that plants consistently change the direction of point bar migration. Specifically, in the absence of vegetation, point bars tend to migrate downstream – like mid-channel bars do in braided rivers.

“In other words, we show that, if one were to use the same criterion geologists use in ancient rocks on modern rivers, meandering rivers would be miscategorized as braided rivers,” Lapôtre said.

Rivers over time

The findings offer a provocative new window into Earth’s past eons, upending the conventional picture of how rivers have sculpted continents. If indeed carbon-loaded floodplains were laid down far more extensively over history, scientists may need to revise models of major natural climate swings over time, with implications for our understanding of ongoing climate change.

“Understanding how our planet is going to respond to human-induced climate change hinges on having an accurate baseline for how it has responded to past perturbations,” Hasson said. “The rock record provides that baseline, but it’s only useful if we interpret it accurately.”

“We’re suggesting that an important control on carbon cycling – where carbon is stored, and for how long, due to river type and floodplain creation – hasn’t been fully understood,” he said. “Our study now points the way to better assessments.”

Additional co-authors are from the University of Padova and the University of British Columbia.

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https://www.sciencedaily.com/releases/2025/08/250831010533.htm

The ancient oxygen flood that forever changed life in the oceans

Source:Duke University

Summary:Ancient forests may have fueled a deep-sea oxygen boost nearly 390 million years ago, unlocking evolutionary opportunities for jawed fish and larger marine animals. New isotopic evidence shows that this permanent oxygenation marked a turning point in Earth’s history — a reminder of how fragile the ocean’s oxygen balance remains today.Share:

    

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Ancient Oxygen Flood Changed Life Forever
An artist’s rendering of a prehistoric jawed fish from the Late Devonian called Dunkleosteus. These sorts of large, active vertebrates evolved shortly after the deep ocean became well-oxygenated. Credit: © 2008 N. Tamura/CC-BY-SA

Some 390 million years ago in the ancient ocean, marine animals began colonizing depths previously uninhabited. New research indicates this underwater migration occurred in response to a permanent increase in deep-ocean oxygen, driven by the aboveground spread of woody plants — precursors to Earth’s first forests. 

That rise in oxygen coincided with a period of remarkable diversification among fish with jaws — the ancestors of most vertebrates alive today. The finding suggests that oxygenation might have shaped evolutionary patterns among prehistoric species.

“It’s known that oxygen is a necessary condition for animal evolution, but the extent to which it is the sufficient condition that can explain trends in animal diversification has been difficult to pin down,” said co-lead author Michael Kipp, assistant professor of earth and climate sciences in the Duke University Nicholas School of the Environment. “This study gives a strong vote that oxygen dictated the timing of early animal evolution, at least for the appearance of jawed vertebrates in deep-ocean habitats.”

For a time, researchers thought that deep-ocean oxygenation occurred once at the beginning of the Paleozoic Era, some 540 million years ago. But more recent studies have suggested that oxygenation occurred in phases, with nearshore waters first becoming livable to breathing organisms, followed by deeper environments.

Kipp and colleagues homed in on the timing of those phases by studying sedimentary rocks that formed under deep seawater. Specifically, they analyzed the rocks for selenium, an element that can be used to determine whether oxygen existed at life-sustaining levels in ancient seas. 

In the marine environment, selenium occurs in different forms called isotopes that vary by weight. Where oxygen levels are high enough to support animal life, the ratio of heavy to light selenium isotopes varies widely. But at oxygen levels prohibitive to most animal life, that ratio is relatively consistent. By determining the ratio of selenium isotopes in marine sediments, researchers can infer whether oxygen levels were sufficient to support animals that breathe underwater.

Working with research repositories around the world, the team assembled 97 rock samples dating back 252 to 541 million years ago. The rocks had been excavated from areas across five continents that, hundreds of millions of years ago, were located along the outermost continental shelves — the edges of continents as they protrude underwater, just before giving way to steep drop-offs.

After a series of steps that entailed pulverizing the rocks, dissolving the resulting powder and purifying selenium, the team analyzed the ratio of selenium isotopes that occurred in each sample.

Their data indicated that two oxygenation events occurred in the deeper waters of the outer continental shelves: a transient episode around 540 million years ago, during a Paleozoic period known as the Cambrian, and an episode that began 393-382 million years ago, during an interval called the Middle Devonian, that has continued to this day. During the intervening millennia, oxygen dropped to levels inhospitable to most animals. The team published their findings in Proceedings of the National Academy of Sciences in August.

“The selenium data tell us that the second oxygenation event was permanent. It began in the Middle Devonian and persisted in our younger rock samples,” said co-lead author Kunmanee “Mac” Bubphamanee, a Ph.D. candidate at the University of Washington.

That event coincided with numerous changes in oceanic evolution and ecosystems — what some researchers refer to as the “mid-Paleozoic marine revolution.” As oxygen became a permanent feature in deeper settings, jawed fish, called gnathostomes, and other animals began invading and diversifying in such habitats, according to the fossil record. Animals also got bigger, perhaps because oxygen supported their growth.

The Middle Devonian oxygenation event also overlapped with the spread of plants with hard stems of wood.

“Our thinking is that, as these woody plants increased in number, they released more oxygen into the air, which led to more oxygen in deeper ocean environments,” said Kipp, who began this research as a Ph.D. student at the University of Washington.

The cause of the first, temporary oxygenation event during the Cambrian is more enigmatic.

“What seems clear is that the drop in oxygen after that initial pulse hindered the spread and diversification of marine animals into those deeper environments of the outer continental shelves,” Kipp said.

Though the team’s focus was on ancient ocean conditions, their findings are relevant now.

“Today, there’s abundant ocean oxygen in equilibrium with the atmosphere. But in some locations, ocean oxygen can drop to undetectable levels. Some of these zones occur through natural processes. But in many cases, they’re driven by nutrients draining off continents from fertilizers and industrial activity that fuel plankton blooms that suck up oxygen when they decay,” Kipp said.

“This work shows very clearly the link between oxygen and animal life in the ocean. This was a balance struck about 400 million years ago, and it would be a shame to disrupt it today in a matter of decades.”

Funding: MAK was supported by an NSF Graduate Research Fellowship and Agouron Institute Postdoctoral Fellowship. Additional support was provided by the NASA Astrobiology Institute’s Virtual Planetary Laboratory.

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https://www.sciencedaily.com/releases/2025/08/250827010726.htm

Wildfires threaten water quality for up to eight years after they burn

A study of 100,000 water samples from 500 river basins found elevated levels of contaminants persist for years after a fire.

Source:University of Colorado at Boulder

Summary:Wildfires don’t just leave behind scorched earth—they leave a toxic legacy in Western rivers that can linger for nearly a decade. A sweeping new study analyzed over 100,000 water samples from more than 500 U.S. watersheds and revealed that contaminants like nitrogen, phosphorus, organic carbon, and sediment remain elevated for up to eight years after a blaze.Share:

    

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Wildfires Leave Rivers Polluted for 8 Years
Wildfires leave a hidden trail: rivers tainted by long-lasting pollution. New research shows water contamination can linger up to eight years, with storms often triggering delayed surges of toxic runoff. Credit: Shutterstock

Years after wildfires burn forests and watersheds, the contaminants left behind continue to poison rivers and streams across the Western U.S. — much longer than scientists estimated.

A new study, published on June 23 in Nature Communications Earth & Environment, analyzed water quality in more than 500 watersheds across the Western U.S., and is the first large-scale assessment of post-wildfire quality.

The research was led by scientists from the Cooperative Institute for Research in Environmental Science (CIRES) at the University of Colorado Boulder.

“We were attempting to look at notable trends in post-wildfire water quality across the entire U.S. West, to help inform water management strategies in preparing for wildfire effects,” said Carli Brucker, lead author and former CU Boulder and Western Water Assessment PhD student.

The results showed contaminants like organic carbon, phosphorus, nitrogen, and sediment can degrade water quality for up to eight years after a fire. Water managers can use this data to help them plan for the future and respond appropriately when wildfires strike.

CIRES Fellow and Western Water Assessment Director Ben Livneh was the principal investigator and co-author of the study. Much of his research focuses on hydrology, or water supply, on a continental scale. When he realized he could use the same approach to understand large-scale trends in water quality, he was excited to test the method.

“There’s been a lot of work, for example, in the National Climate Assessment and the International Panel on Climate Change talking about changes in global water supply,” said Livneh, associate professor in the Department of Civil, Environmental and Architectural Engineering. “But those assessments point to this gap in water quality assessments in a continental scale context, whereas people like me in physical hydrology have been thinking about the continental scale challenges for a while.”

Researchers have long known that fire ash and soil destruction contribute to degraded water quality. Yet, past research has largely been limited to state and municipal studies — cities and towns test water quality in local streams and rivers following large fires.

For the new study, the team analyzed more than 100,000 water samples from 500 sites: half from burned river basins and half from unburned. They measured levels of organic carbon, nitrogen, phosphorus, and sediment as well as turbidity, or cloudiness, of each sample.

To understand wildfire-driven impacts, the team built data-driven models to measure how much contaminants changed in each basin before and after wildfires. In the final step, they compiled data to find the average across the burned basins for each pre- and post-wildfire year, and then compared those to the unburned basins.

The results showed watersheds take longer to recover after wildfires than previous studies found. Organic carbon, phosphorus, and turbidity are significantly elevated in the first one to five years post-fire. Nitrogen and sediment show significant increases up to eight years post-fire. Fire-driven impacts were worse in more forested areas.

“It can take two years, up to eight years, for the effect to be fully felt,” Livneh said. “Sometimes it can be a delayed effect, meaning, it’s not all happening right away, or sometimes you need a big enough storm that will mobilize enough of the leftover contaminants.”

Each watershed in the study felt the impacts differently. This is likely tied to where the fire struck — a fire closer to the river would be worse than an upstream fire. Different soils, vegetation, and weather also change the impact in each watershed, making it difficult to plan for the future.

“There’s a huge amount of variability in sedimentation rates,” said Brucker, who now works as a consultant. “Some streams are completely clear of sediment after wildfires, and some have 2000 times the amount of sediment.”

Despite variability across river basins, the study provides concrete numbers that give insight to water managers across the Western U.S. Researchers hope the results provide better direction on informing future planning efforts for increasing wildfire resilience.

“I’m hoping that providing concrete numbers is very impactful to water managers,” Brucker said. “You can’t fund resilience improvements on general concerns alone. Water managers need real numbers for planning, and that’s what we’re providing,” Brucker said.

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https://www.sciencedaily.com/releases/2025/06/250624044332.htm#google_vignette

Protected seas help kelp forests bounce back from heatwaves

Date:August 20, 2025

Source:British Ecological Society

Summary:Kelp forests bounce back faster from marine heatwaves when shielded inside Marine Protected Areas. UCLA researchers found that fishing restrictions and predator protection strengthen ecosystem resilience, though results vary by location.Share:

    

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Protected Seas Help Kelp Forests Bounce Back
Marine Protected Areas give kelp forests a recovery edge after heatwaves, showing that local protections can buffer global climate pressures. Credit: Shutterstock

New research finds that Marine Protected Areas can boost the recovery of globally important kelp forests following marine heatwaves. The findings are published in the British Ecological Society’s Journal of Applied Ecology.

Using four decades of satellite images, University of California, Los Angeles (UCLA) researchers have looked at impacts Marine Protected Areas (MPAs) are having on kelp forests along the coast of California.

They found that although the overall effect of MPAs on kelp forest cover was modest, the benefits became clear in the aftermath of marine heatwaves in 2014-2016, when kelp forests within MPAs were able recover more quickly, particularly in southern California.

“We found that kelp forests inside MPAs showed better recovery after a major climate disturbance compared to similar unprotected areas.” Explained Emelly Ortiz-Villa, lead author of the study and a PhD researcher at UCLA Department of Geography.

“Places where fishing is restricted and important predators like lobsters and sheephead are protected saw stronger kelp regrowth. This suggests that MPAs can support ecosystem resilience to climate events like marine heatwaves.”

Professor Rick Stafford, Chair of the British Ecological Society Policy Committee, who was not involved in the study said: “It’s great to see these results and they clearly show that local action to protect biodiversity and ecosystem function can help prevent changes caused by global pressures such as climate change.

“However, it also demonstrates the need for effective MPAs. In this study, all the MPAs examined regulated fishing activity, and this is not the case for many sites which are designated as MPAs worldwide – including many in the UK.”

Kelp forests: a globally important and threatened ecosystem

Kelp forests our found around coastlines all over the world, particularly in cool, temperate waters such as the pacific coast of North America, The UK, South Africa, and Australia.

These complex ecosystems are havens for marine wildlife, including commercially important fish, and are one of the most productive habitats on Earth. They’re also efficient in capturing carbon and protect coastlines by buffering against wave energy.

However, kelp forests across the west coast of North America have declined in recent yeadue to pressures such as marine heatwaves, made more frequent and intense with climate change, and predation from increasing numbers of sea urchins, which have benefitted from population collapses of sea stars, which predate them.

Kyle Cavanaugh, a senior author of the study and professor in the UCLA Department of Geography and Institute of the Environment and Sustainability said: “Kelp forests are facing many threats, including ocean warming, overgrazing, and pollution. These forests can be remarkably resilient to individual stressors, but multi-stressor situations can overwhelm their capacity to recover. By mitigating certain stressors, MPAs can help enhance the resilience of kelp.”

Marine protected areas as a conservation tool

MPAs are designated areas of the ocean where human activity is limited to support ecosystems and the species living there. However, protections vary widely and while some areas are no-take zones, others have few restrictions or lack comprehensive management and enforcement. Many even allow destructive practices like bottom trawling.

Effective MPAs form a key part of the Kunming-Montreal Global Biodiversity Framework, agreed at COP15 in 2022, which commits nations to protecting at least 30% of oceans and land by 2030.

“Our findings can inform decisions about where to establish new MPAs or implement other spatial protection measures.” said Kyle Cavanaugh. “MPAs will be most effective when located in areas that are inherently more resilient to ocean warming, such as regions with localized upwelling or kelp populations with higher thermal tolerance.”

Emelly Villa added: “Our findings suggest that kelp forests could be a useful indicator for tracking the ecological health and climate resilience of protected areas and should be included in long-term monitoring strategies.”

Measuring the impact of marine protected areas

To understand the effects MPAs were having on kelp, the researchers used of satellite data from 1984-2022 to compare kelp forests inside and outside of 54 MPAs along the California coast.

By matching each MPA with a reference site with similar environmental conditions, they were able to test whether MPAs helped kelp forests resist loss or recover from extreme marine heatwaves which took place in the North pacific between 2014 and 2016.

The researchers warn that while their findings show that MPAs can help kelp recovery after marine heatwaves, the effect was highly variable depending on location.

“On average, kelp within MPAs showed greater recovery than in the reference sites. However, not all MPAs outperformed their corresponding reference sites, suggesting that additional factors are also play a role in determining resilience.” said Kyle Cavanaugh.

The researchers say that future work could look to identify these factors to better understand where and when MPAs are most effective at enhancing kelp resilience.

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https://www.sciencedaily.com/releases/2025/08/250820000805.htm#google_vignette

Scientists reveal how just two human decisions rewired the Great Salt Lake forever

Utah geoscientist’s analysis of carbon and oxygen isotopes documents profound human-driven changes arising from agriculture and rail causeway.

Source: University of Utah

Summary:Scientists found that Great Salt Lake’s chemistry and water balance were stable for thousands of years, until human settlement. Irrigation and farming in the 1800s and a railroad causeway in 1959 created dramatic, lasting changes. The lake now behaves in ways unseen for at least 2,000 years.Share:

    

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Two Human Decisions Rewired the Great Salt Lake
The view of Great Salt Lake’s North Arm from Gunnison Island, which has long served as a nesting ground for pelicans. Credit: Brian Maffly, University of Utah

Over the past 8,000 years, Utah’s Great Salt Lake has been sensitive to changes in climate and water inflow. Now, new sediment isotope data indicate that human activity over the past 200 years has pushed the lake into a biogeochemical state not seen for at least 2,000 years.

A University of Utah geoscientist applied isotope analysis to sediments recovered from the lake’s bed to characterize changes to the lake and its surrounding watershed back to the time the lake took its current shape from the vast freshwater Lake Bonneville that once covered much of northern Utah.

“Lakes are great integrators. They’re a point of focus for water, for sediments, and also for carbon and nutrients,” said Gabriel Bowen, a professor and chairman of the Department of Geology & Geophysics. “We can go to lakes like this and look at their sediments and they tell us a lot about the surrounding landscape.”

Sedimentary records provide context for ongoing changes in terminal saline lakes, which support fragile, yet vital ecosystems, and may help define targets for their management, according to Bowen’s new study, published last month in Geophysical Research Letters.

This research helps fill critical gaps in the lake’s geological and hydrological records, coming at a time when the drought-depleted level of the terminal body has been hovering near its historic low.

“We have all these great observations, so much monitoring, so much information and interest in what’s happening today. We also have a legacy of people looking at the huge changes in the lake that happened over tens of thousands and hundreds of thousands of years,” Bowen said. “What we’ve been missing is the scale in the middle.”

That is the time spanning the first arrival of white settlers in Utah but after Lake Bonneville receded to become Great Salt Lake.

By analyzing oxygen and carbon isotopes preserved in lake sediments, the study reconstructs the lake’s water and carbon budgets through time. Two distinct, human-driven shifts stand out:

  • Mid-19th century – Coinciding with Mormon settlement in 1847, irrigation rapidly greened the landscape around the lake, increasing the flow of organic matter into the lake and altering its carbon cycle.
  • Mid-20th century – Construction of the railroad causeway in 1959 disrupted water flow between the lake’s north and south arms, which turned Gilbert Bay from a terminal lake to an open one that partially drained into Gunnison Bay, altering the salinity and water balance to values rarely seen in thousands of years.

The new study examines two sets of sediment cores extracted from the bed of Great Salt Lake, each representing different timescales. The top 10 meters of the first core, drilled in the year 2000 south of Fremont Island, contains sediments washed into the lake up to 8,000 years ago.

The view of the Great Salt Lake from Gunnison Island, which has long served as a nesting ground for pelicans. Credit: Brian Maffly

The other samples, recovered by the U.S. Geological Survey, represent only the upper 30 centimeters of sediments, deposited in the last few hundred years.

“The first gives us a look at what was happening for the 8,000 years before the settlers showed up here,” Bowen said. “The second are these shallower cores that allow us to see how the lake changed after the arrival of the settlers.”

Bowen subjected these lakebed sediments at varying depths to an analysis that determines isotope ratios of carbon and oxygen, shedding light on the landscape surrounding the lake and the water in the lake at varying points in the past.

“The carbon tells us about the biogeochemistry, about how the carbon cycles through the lake, and that’s affected by things like weathering of rocks that bring carbon to the lake and the vegetation in the watershed, which also contributes carbon that dissolves into the water and flows to the lake,” he said.

Bowen’s analysis documented a sharp change in carbon, indicating profound changes that coincided with the arrival of Mormon pioneers in the Salt Lake Valley, where they introduced irrigated agriculture to support a rapidly growing community.

“We see a big shift in the carbon isotopes, and it shifts from values that are more indicative of rock weathering, carbon coming into the lake from dissolving limestone, toward more organic sources, more vegetation sources,” Bowen said.

The new carbon balance after settlement was unprecedented during the 8,000 years of record following the demise of Lake Bonneville.

Next, Bowen’s oxygen isotope analysis reconstructed the lake’s water balance over time.

“Essentially, it tells us about the balance of evaporation and water inflow into the lake. As the lake is expanding, the oxygen isotope ratio goes down. As the lake shrinks, it goes up, basically telling us about the rate of change of the lake volume. We see little fluctuations, but nothing major until we get to 1959.”

That’s the year Union Pacific built a 20-mile causeway to replace a historic rail trestle, dividing the lake’s North Arm, which has no tributaries, from its South Arm, also known as Gilbert Bay, which receives inflow from three rivers. Water flows through a gap in the causeway into North Arm, now rendering the South Arm an open system.

“We changed the hydrology of the lake fundamentally and gave it an outflow. We see that really clearly in the oxygen isotopes, which start behaving in a different way,” he said. Counterintuitively, the impact of this change was to make Gilbert Bay waters fresher than they would have been otherwise, buying time to deal with falling lake levels and increasing salinity due to other causes.

“If we look at the longer time scale, 8,000 years, the lake has mostly been pinned at a high evaporation state. It’s been essentially in a shrinking, consolidating state throughout that time. And that only reversed when we put in the causeway.”

The paper, “Multi-millennial context for post-colonial hydroecological change in Great Salt Lake,” was posted online July 22 in the journal Geophysical Research Letters. Gabriel Bowen is the sole author and is supported by grants from the National Science Foundation.

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https://www.sciencedaily.com/releases/2025/08/250818102953.htm

Drought Stalks Serbia, Harming Livestock

By Reuters

U.S. News & World Report

Reuters

REUTERS

A drone view shows a herd of cattle searching for water amid a severe drought that has dried up Suva Planina mountain’s main springs, near the town of Bela Palanka, Serbia August 12, 2025. REUTERS/Djordje Kojadinovic

SUVA PLANINA, Serbia (Reuters) -A prolonged drought and sweltering heat are taking their toll on villagers, livestock and crops in the mountains of southeastern Serbia, with animals starting to die.

Lack of rainfall since May has caused water shortages, wildfires and disruption to agriculture across the Western Balkans, also comprised of Montenegro, Bosnia, Albania, Kosovo and North Macedonia,

At Serbia’s Suva Planina (Dry Mountain), owners who take their cows and horses for summer grazing said the springs dried up too early this year.

“There’s not a drop of water … animals are starting to die,” said Ljubisa Petkovic, a herder from the nearby municipality of Gadzin Han.

Around 1,000 thirsty cows and horses milled round a few watering holes and springs, sipping sparse and dirty water from puddles.

Temperatures in Serbia on Tuesday stood at around 35 degrees Celsius (95 Fahrenheit) with several wildfires burning.

In late July, local authorities, alerted by cattle owners, drove water trucks up the Suva Planina pastures, filled a pond, and pledged to send more.

Nikola Manojlovic, 35, said he hoped for more state water supplies and warned that villages in the valley were also suffering from the drought.

MORE:  Places the U.S. Government Warns Not to Travel Right Now

“Corn has dried up … we’ve had no running water in the village for three months now and we have no water here,” Manojlovic said.

Meteorologists say Serbia may have a spell of rainy weather later this month, but it may not be enough to replenish the small rivers, lakes and creeks needed for the cattle to drink.

(Reporting by Branko Filipovicc; Writing by Aleksandar Vasovic; Editing by Andrew Cawthorne)

Copyright 2025 Thomson Reuters.

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https://www.usnews.com/news/world/articles/2025-08-12/drought-stalks-serbia-harming-livestock