Finding new physics in debris from colliding neutron stars

Neutron star mergers are a treasure trove for new physics signals, with implications for determining the true nature of dark matter, according to research from Washington University in St. Louis.

On Aug. 17, 2017, the Laser Interferometer Gravitational-wave Observatory (LIGO), in the United States, and Virgo, a detector in Italy, detected gravitational waves from the collision of two neutron stars. For the first time, this astronomical event was not only heard in gravitational waves but also seen in light by dozens of telescopes on the ground and in space.

Physicist Bhupal Dev in Arts & Sciences used observations from this neutron star merger -- an event identified in astronomical circles as GW170817 -- to derive new constraints on axion-like particles. These hypothetical particles have not been directly observed, but they appear in many extensions of the standard model of physics.

Axions and axion-like particles are leading candidates to compose part or all of the "missing" matter, or dark matter, of the universe that scientists have not been able to account for yet. At the very least, these feebly-interacting particles can serve as a kind of portal, connecting the visible sector that humans know much about to the unknown dark sector of the universe.

"We have good reason to suspect that new physics beyond the standard model might be lurking just around the corner," said Dev, first author of the study in Physical Review Letters and a faculty fellow of the university's McDonnell Center for the Space Sciences.

When two neutron stars merge, a hot, dense remnant is formed for a brief period of time. This remnant is an ideal breeding ground for exotic particle production, Dev said. "The remnant gets much hotter than the individual stars for about a second before settling down into a bigger neutron star or a black hole, depending on the initial masses," he said.

These new particles quietly escape the debris of the collision and, far away from their source, can decay into known particles, typically photons. Dev and his team -- including WashU alum Steven Harris (now NP3M fellow at Indiana University), as well as Jean-Francois Fortin, Kuver Sinha and Yongchao Zhang -- showed that these escaped particles give rise to unique electromagnetic signals that can be detected by gamma-ray telescopes, such as NASA's Fermi-LAT.

The research team analyzed spectral and temporal information from these electromagnetic signals and determined that they could distinguish the signals from the known astrophysical background. Then they used Fermi-LAT data on GW170817 to derive new constraints on the axion-photon coupling as a function of the axion mass. These astrophysical constraints are complementary to those coming from laboratory experiments, such as ADMX, which probe a different region of the axion parameter space.

In the future, scientists could use existing gamma-ray space telescopes, like the Fermi-LAT, or proposed gamma-ray missions, like the WashU-led Advanced Particle-astrophysics Telescope (APT), to take other measurements during neutron star collisions and help improve upon their understanding of axion-like particles.

"Extreme astrophysical environments, like neutron star mergers, provide a new window of opportunity in our quest for dark sector particles like axions, which might hold the key to understanding the missing 85% of all the matter in the universe," Dev said.

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Herbivores, displaced by ocean warming, threaten subtropical seagrass meadows

Tropical herbivores are on the move, and that could spell trouble for subtropical seagrass meadows.

As the ocean warms, marine species often travel poleward in search of suitable habitats and food.

This phenomenon, known as tropicalization, can expand the range of tropical herbivores such as sea turtles and manatees -- which prefer warmer waters -- to subtropical regions that have historically supported few marine herbivores.

A new study published in Nature Ecology & Evolution describes how subtropical seagrasses are at risk as tropical herbivores move in response to warming oceans.

"Ocean warming poses multiple threats to marine ecosystems," said Tom Frazer, co-author of the study, and professor and dean of the University of South Florida College of Marine Science.

"Seagrass meadows, which provide forage for herbivores and nursery habitat for many recreational and commercially important fishery species, are already threatened by degraded water quality. This study suggests that the tropicalization of marine ecosystems in response to warming temperatures could further contribute to the decline of these vital habitats."

The study's authors used turtlegrass, a foundational seagrass species found throughout the Western Atlantic, Caribbean Sea and Gulf of Mexico, as a model for seagrass meadows.

Researchers conducted a series of coordinated experiments in seagrass beds spanning 23 degrees of latitude (including sites in Bonaire, Panama, Belize, Mexico, the Cayman Islands, and the United States) and found that turtlegrass populations at higher latitudes had lower productivity in response to simulated grazing than populations at lower latitudes.

The findings suggest that subtropical seagrasses are less resilient to heavy grazing from marine herbivores, in part because they receive less sunlight relative to their tropical counterparts.

As tropical herbivores move into subtropical waters, overgrazing may prevent subtropical seagrass meadows from persisting in these environments.

There's hope, though, for subtropical seagrasses and the many species they sustain.

What's key, according to the study's authors, is making sure seagrasses have what they need to thrive.

"If we want to give these meadows the best chance of enduring the anticipated increases in grazing, we need to get them as much light as possible," said Justin Campbell, lead author and marine biologist at Florida International University.

"That means protecting the water quality."

While overgrazing is not yet a widespread occurrence across the Western Atlantic, it already occurs in subtropical to temperate waters around Australia and in the Mediterranean.

This recent study can serve as a clarion call to protect subtropical seagrass meadows before grazing pressure from tropical herbivores increases.

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Sinking land increases risk for thousands of coastal residents by 2050

One in 50 people living in two dozen coastal cities in the United States could experience significant flooding by 2050, according to Virginia Tech-led research.

Published in Nature, the study combines satellite-obtained measurements of sinking land, also known as subsidence, with sea-level rise projections and tide charts to provide a new comprehensive look at the potential for flooding in a combined 32 cities along the Atlantic, Pacific, and Gulf coasts. The study projects that in the next three decades as many as 500,000 people could be affected as well as a potential 1 in 35 privately owned properties damaged by flooding. The study also highlights the racial and socioeconomic demographics of those potentially affected.

"One of the challenges we have with communicating the issue of sea-level rise and land subsidence broadly is it often seems like a long-term problem, like something whose impacts will only manifest at the end of the century, which many people may not care about," said lead author Leonard Ohenhen, a graduate student working with Associate Professor Manoochehr Shirzaei at Virginia Tech's Earth Observation and Innovation Lab. "What we've done here is focused the picture on the short term, just 26 years from now."

Other increases compared to current estimates include:

• Between 500 and 700 more square miles of land flooded
• 176,000 to 518,000 more people affected
• 94,000 to 288,000 more properties exposed with an estimated value of $32 billion to $109 billion

"The whole purpose of this paper is to provide data to support decisions," Shirzaei said. "Every city, every county has a flood resiliency plan in place. They are required by law to create that. But it's likely nobody has received the entire picture until this study, which creates probably the first comprehensive picture of what's happen in the not-too-distant future."

Collaborators on the study include:

• Chandrakanta Ojha of the India Institute of Science Education and Research in Punjab, India
• Sonam Sherpa, a former Ph.D. student at Virginia Tech and a postdoctoral scholar at Brown University
• Robert J. Nicholls of the Tyndall Centre for Climate Change Research at the University of East Anglia, United Kingdom

"This study demonstrates that we can now measure vertical land motion at a sufficient scale to create a useful climate service that supports planning and management decisions on flooding," said Nicholls, a professor of climate adaptation. "This approach has the potential to be applied in any city around the world, really supporting adaptation."

Using highly accurate data points measured by space-based radar satellites, Shirzaei and his research team have built some of the world's first high-resolution depictions of the sinking land along the coast of the entire United States. Their work has previously revealed regions of the Atlantic coast to be sinking by as much as 5 millimeters per year.

This study revealed that 24 of the 32 coastal cities are currently sinking more than 2 millimeters per year and half of those cities have areas sinking more than global seas are rising. These numbers might seem small, but when combined with sea-level rise over time, it adds up to quite a significant shift, according to Ohenhen.

"The analogy I have found that is really helpful in helping people understand this change is to think about a sinking boat," he said. "Imagine you are in that boat with a steady leak, slowly causing the boat to sink. That leak symbolizes sea-level rise or broadly flooding. What would happen if it also starts raining? Even a minor rainfall or drizzle would cause the boat to sink more quickly than you thought it would. That's what land subsidence does -- even imperceptible millimeter land subsidence exacerbates existing coastal hazards."

Along with the new flood projections, the study also revealed the 32 cities have a combined 131 flood control structures, such as levees, berms, or dikes, but that 50 percent of those are located on the California coast. Only three of the 11 Atlantic coast cities studied maintain levees or floodwalls.

"When we looked at it across the board, we found that there is a general unappreciation for flood protection, particularly on the Atlantic coast," Ohenhen said. "And even the levees there often protect less than 10 percent of the city, compared to other cities on the Pacific or Gulf coasts where up to 70 percent is protected."

Another first in the study is the consideration of racial and socioeconomic demographics related to the potentially affected areas.

In some cities examined, particularly those along the Gulf Coast, the potential increased exposure fell disproportionately on racial minorities. In other cities, the properties facing increased exposure were found to generally be of lesser value than the median property value of the area. And in a few cities, New Orleans and Port Arthur, Texas, particularly, these two demographics intersect, showing the areas with greatest potential risk to be disproportionately occupied by people of color who are also at an economic disadvantage when compared to the city as a whole.

"That was the most surprising part of the study," Ohenhen said. "We found that there is racial and economic inequality in those areas in that there was an overrepresentation of historically marginalized groups potentially impacted as well as properties with significantly lower value than the rest of the cities. It really multiplies the potential impact to those areas and their abilities to recover from significant flooding."

Shirzaei said he believes the study as a whole not only provides the clearest picture of potential flooding to date, but also should serve as a call to action for policymakers of those areas.

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Baby quasars: Growing supermassive black holes

The James Webb Space Telescope makes one of the most unexpected findings within its first year of service: A high number of faint little red dots in the distant Universe could change the way we understand the genesis of supermassive black holes. The research, led by Jorryt Matthee, Assistant Professor in astrophysics at the Institute of Science and Technology Austria (ISTA), is now published in The Astrophysical Journal.

A bunch of little red dots found in a tiny region of our night sky might be an unexpected breakthrough for the James Webb Space Telescope (JWST) within its first year of service. These objects were indistinguishable from normal galaxies through the 'eyes' of the older Hubble Space Telescope. "Without having been developed for this specific purpose, the JWST helped us determine that faint little red dots-found very far away in the Universe's distant past-are small versions of extremely massive black holes. These special objects could change the way we think about the genesis of black holes," says Jorryt Matthee, Assistant Professor at the Institute of Science and Technology Austria (ISTA), and lead author of the study. "The present findings could bring us one step closer to answering one of the greatest dilemmas in astronomy: According to the current models, some supermassive black holes in the early Universe have simply grown 'too fast'. Then how did they form?"

The cosmic points of no return

Scientists have long considered black holes a mathematical curiosity until their existence became increasingly evident. These strange cosmic bottomless pits could have such compact masses and strong gravities that nothing can escape their force of attraction-they suck in anything, including cosmic dust, planets, and stars, and deform the space and time around them such that even light cannot escape. The general theory of relativity, published by Albert Einstein over a century ago, predicted that black holes could have any mass. Some of the most intriguing black holes are the supermassive black holes (SMBHs), which could reach millions to billions of times the mass of the Sun. Astrophysicists agree that there is an SMBH at the center of almost every large galaxy. The proof that Sagittarius A* is an SMBH in the center of our Galaxy with over four million times the Sun's mass, earned the 2020 Nobel Prize in Physics.

Too massive to be there

However, not all SMBHs are the same. While Sagittarius A* could be compared to a sleeping volcano, some SMBHs grow extremely rapidly by engulfing astronomic amounts of matter. Thus, they become so luminous that they can be observed until the edge of the ever-expanding Universe. These SMBHs are called quasars and are among the brightest objects in the Universe. "One issue with quasars is that some of them seem to be overly massive, too massive given the age of the Universe at which the quasars are observed. We call them the 'problematic quasars,'" says Matthee. "If we consider that quasars originate from the explosions of massive stars-and that we know their maximum growth rate from the general laws of physics, some of them look like they have grown faster than is possible. It's like looking at a five-year-old child that is two meters tall. Something doesn't add up," he explains. Could SMBHs perhaps grow even faster than we originally thought? Or do they form differently?

Small versions of giant cosmic monsters

Now, Matthee and his colleagues identify a population of objects that appear as little red dots in JWST images. Also, they demonstrate that these objects are SMBHs, but not overly massive ones. Central in determining that these objects are SMBHs was the detection of Hα spectral emission lines with wide line profiles. Hα lines are spectral lines in the deep-red region of visible light that are emitted when hydrogen atoms are heated. The width of the spectra traces the motion of the gas. "The wider the base of the Hα lines, the higher the gas velocity. Thus, these spectra tell us that we are looking at a very small gas cloud that moves extremely rapidly and orbits something very massive like an SMBH," says Matthee. However, the little red dots are not the giant cosmic monsters found in overly massive SMBHs. "While the 'problematic quasars' are blue, extremely bright, and reach billions of times the mass of the Sun, the little red dots are more like 'baby quasars.' Their masses lie between ten and a hundred million solar masses. Also, they appear red because they are dusty. The dust obscures the black holes and reddens the colors," says Matthee. But eventually, the outflow of gas from the black holes will puncture the dust cocoon, and giants will evolve from these little red dots. Thus, the ISTA astrophysicist and his team suggest that the little red dots are small, red versions of giant blue SMBHs in the phase that predates the problematic quasars. "Studying baby versions of the overly massive SMBHs in more detail will allow us to better understand how problematic quasars come to exist."

A "breakthrough" technology

Matthee and his team could find the baby quasars thanks to the datasets acquired by the EIGER (Emission-line galaxies and Intergalactic Gas in the Epoch of Reionization) and FRESCO (First Reionization Epoch Spectroscopically Complete Observations) collaborations. These are a large and a medium JWST program in which Matthee was involved. Last December, the Physics World magazine listed EIGER among the top 10 breakthroughs of the year for 2023. "EIGER was designed to study specifically the rare blue supermassive quasars and their environments. It was not designed to find the little red dots. But we found them by chance in the same dataset. This is because, by using the JWST's Near Infrared Camera, EIGER acquires emission spectra of all objects in the Universe," says Matthee. "If you raise your index finger and extend your arm completely, the region of the night sky we explored corresponds to roughly a twentieth of the surface of your nail. So far, we have probably only scratched the surface."

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Short-term exposure to high levels of air pollution kills 1 million globally every year

Every year, more than one million deaths globally occur because of exposure to short-term (hours to days) fine particulate matter (PM2.5) in air pollution, according to a new report, with Eastern Asia reporting more than 50% of deaths attributable to short-term PM2.5 globally.

To date most studies have focused on the health impacts of living in cities where pollution levels are consistently high, ignoring the frequent "spikes" in pollution that can impact smaller urban areas that occur for instance landscape fires, dust, and other intermittent extreme air-pollution concentration events.

The Monash University study, looking at mortality and pollution levels of PM2.5 in over 13,000 cities and towns across the globe in the two decades to 2019, is published today in The Lancet Planetary Health.

Led by Professor Yuming Guo, the study is important because it is the first to look at short-term exposure globally -- rather than the long-term impacts of persistent exposure such as for people living in cities with high pollution levels.

The researchers found that breathing in PM2.5 for even a few hours, and up to a few days, results in more than one million premature deaths occurring worldwide every year, particularly in Asia and Africa, and more than a fifth (22.74%) of them occurred in urban areas.

According to Professor Guo, the short-term health effects of being exposed to air pollution have been well documented, "such as the megafires in Australia during the so-called Black Summer of 2019-20 which were estimated to have led to 429 smoke-related premature deaths and 3230 hospital admissions as a result of acute and persistent exposure to extremely high levels of bushfire-related air pollution," he said.

"But this is the first study to map the global impacts of these short bursts of air pollution exposure."

The authors add that because of the high population densities in urban areas together with high levels of air pollution, "understanding the mortality burden associated with short-term exposure toPM2.5 in such areas is crucial for mitigating the negative effects of air pollution on the urban population."

According to the study:

• Asia accounted for approximately 65.2% of global mortality due to short-term PM2.5 exposure
• Africa 17.0%
• Europe 12.1%
• The Americas 5.6%
• Oceania 0.1%

The mortality burden was highest in crowded, highly polluted areas in eastern Asia, southern Asia, and western Africa with the fraction of deaths attributable to short-term PM2.5 exposure in eastern Asia was more than 50% higher than the global average.

Most areas in Australia saw a small decrease in the number of attributable deaths, but the attributable death fraction increased from 0.54% in 2000 to 0.76% in 2019, which was larger than any other subregions.

One potential reason could be the increasing frequency and scale of extreme weather-related air pollution events, such as bushfire events in 2019.

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Daily step count of 9,000 to 10,000 may counteract risk of death and cardiovascular disease in highly sedentary people

In good news for office workers, a new study from the University of Sydney's Charles Perkins Centre (Australia) has found increasing your step count may counteract the health consequences of too much sedentary time each day.

The study of over 72,000 people, published in the British Journal of Sports Medicine, found every additional step up to around 10,000 steps a day was linked to reduced risk of death (39 percent) and cardiovascular disease (21 percent) regardless of how much remaining time was spent sedentary.

Previous studies have shown an association between greater daily step count and lower levels of death and CVD, and separate studies have linked high levels of sedentary behaviour with increased risks of CVD and death. However, this is the first to objectively measure, via wrist-worn wearables, if daily steps could offset the health risks of high sedentary behaviour.

Lead author and research fellow, Dr Matthew Ahmadi said: "This is by no means a get out of jail card for people who are sedentary for excessive periods of time, however, it does hold an important public health message that all movement matters and that people can and should try to offset the health consequences of unavoidable sedentary time by upping their daily step count."

Senior author Professor Emmanuel Stamatakis, Director of the Mackenzie Wearables Research Hub at the Charles Perkins Centre, said this growing body of physical activity research using device-based measurement provided huge opportunities for public health.

"Step count is a tangible and easily understood measure of physical activity that can help people in the community, and indeed health professionals, accurately monitor physical activity. We hope this evidence will inform the first generation of device-based physical activity and sedentary behaviour guidelines, which should include key recommendations on daily stepping," said Professor Stamatakis.

How the study was conducted

Researchers used data on 72,174 individuals (average age 61; 58% female) from the UK Biobank study -- a major biomedical database -- who had worn an accelerometer device on their wrist for seven days to measure their physical activity. The accelerometer data were used to estimate daily step count and time spent sedentary, that is sitting or lying down while awake.

The research team then followed the health trajectory of the participants by linking hospitalisation data and death records.

The median daily step count for participants was 6222 steps/day, and 2200 steps/day (the lowest 5 percent of daily steps among all participants) was taken as the comparator for assessing the impact on death and CVD events of increasing step count.

The median time spent sedentary was 10.6 hours/day, so study participants sedentary for 10.5 hours/day or more were considered to have high sedentary time while those who spent less than 10.5 hours/day sedentary were classified as low sedentary time.

Adjustments were made to eliminate biases, such as excluding participants with poor health, who were underweight or had a health event within two years of follow-up. Researchers also took into account factors such as age, sex, ethnicity, education, smoking status, alcohol consumption, diet and parental history of CVD and cancer.

Findings

Over an average 6.9 years follow up, 1633 deaths and 6190 CVD events occurred.

After taking account of other potential influences, the authors calculated that the optimal number of steps per day to counteract high sedentary time was between 9000 to 10000 steps/day, which lowered mortality risk by 39 percent and incident CVD risk by 21 percent.

In both cases, 50 percent of the benefit was achieved at between 4000 and 4500 steps a day.

Study limitations

This is an observational study so can't establish direct cause and effect. And although the large sample size and long follow-up allowed the risk of bias to be reduced, the authors acknowledge the possibility that other unmeasured factors could affect results. As steps and sedentary time were obtained in a single time point, this could also lead to bias, they add.

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Bee-2-Bee influencing: Bees master complex tasks through social interaction

In a groundbreaking discovery, bumblebees have been shown to possess a previously unseen level of cognitive sophistication. A new study, published in Nature, reveals that these fuzzy pollinators can learn complex, multi-step tasks through social interaction, even if they cannot figure them out on their own. This challenges the long-held belief that such advanced social learning is unique to humans, and even hints at the presence of key elements of cumulative culture in these insects.

Led by Dr Alice Bridges and Professor Lars Chittka , the research team designed a two-step puzzle box requiring bumblebees to perform two distinct actions in sequence to access a sweet reward at the end.

Training bees to do this was no easy task, and bees had to be helped along by the addition of an extra reward along the way.

This temporary reward was eventually taken away, and bees subsequently had to open the whole box before getting their treat.

Surprisingly, while individual bees struggled to solve the puzzle when starting from scratch, those allowed to observe a trained "demonstrator" bee readily learned the entire sequence -- even the first step -- while only getting a reward at the end.

This study demonstrates that bumblebees possess a level of social learning previously thought to be exclusive to humans.

They can share and acquire behaviours that are beyond their individual cognitive capabilities: an ability thought to underpin the expansive, complex nature of human culture, and one previously thought to be exclusive to us.

Dr Bridges emphasises the novelty of this finding: "This is an extremely difficult task for bees. They had to learn two steps to get the reward, with the first behaviour in the sequence being unrewarded. We initially needed to train demonstrator bees with a temporary reward included there, highlighting the complexity. Yet, other bees learned the whole sequence from social observation of these trained bees, even without ever experiencing the first step's reward. But when we let other bees attempt to open the box without a trained bee to demonstrate the solution, they didn't manage to open any at all."

Beyond individual learning, this research opens exciting possibilities for understanding the emergence of cumulative culture in the animal kingdom.

Cumulative culture refers to the gradual accumulation of knowledge and skills over generations, allowing for increasingly complex behaviours to develop.

The bees' ability to learn such a complex task from a demonstrator suggests a potential pathway for cultural transmission and innovation beyond their individual learning capabilities.

Professor Chittka further underscores the implications: "This challenges the traditional view that only humans can socially learn complex behaviour beyond individual learning. It raises the fascinating possibility that many of the most remarkable accomplishments of the social insects, like the nesting architectures of bees and wasps or the agricultural habits of aphid- and fungus-farming ants, may have initially spread by copying of clever innovators, before they eventually became part of the species-specific behaviour repertoires."

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Astronomers spot oldest 'dead' galaxy yet observed

A galaxy that suddenly stopped forming new stars more than 13 billion years ago has been observed by astronomers.

Using the James Webb Space Telescope, an international team of astronomers led by the University of Cambridge have spotted a 'dead' galaxy when the universe was just 700 million years old, the oldest such galaxy ever observed.

This galaxy appears to have lived fast and died young: star formation happened quickly and stopped almost as quickly, which is unexpected for so early in the universe's evolution. However, it is unclear whether this galaxy's 'quenched' state is temporary or permanent, and what caused it to stop forming new stars.

The results, reported in the journal Nature, could be important to help astronomers understand how and why galaxies stop forming new stars, and whether the factors affecting star formation have changed over billions of years.

"The first few hundred million years of the universe was a very active phase, with lots of gas clouds collapsing to form new stars," said Tobias Looser from the Kavli Institute for Cosmology, the paper's first author. "Galaxies need a rich supply of gas to form new stars, and the early universe was like an all-you-can-eat buffet."

"It's only later in the universe that we start to see galaxies stop forming stars, whether that's due to a black hole or something else," said co-author Dr Francesco D'Eugenio, also from the Kavli Institute for Cosmology.

Astronomers believe that star formation can be slowed or stopped by different factors, all of which will starve a galaxy of the gas it needs to form new stars. Internal factors, such as a supermassive black hole or feedback from star formation, can push gas out of the galaxy, causing star formation to stop rapidly. Alternatively, gas can be consumed very quickly by star formation, without being promptly replenished by fresh gas from the surroundings of the galaxy, resulting in galaxy starvation.

"We're not sure if any of those scenarios can explain what we've now seen with Webb," said co-author Professor Roberto Maiolino. "Until now, to understand the early universe, we've used models based on the modern universe. But now that we can see so much further back in time, and observe that the star formation was quenched so rapidly in this galaxy, models based on the modern universe may need to be revisited."

Using data from JADES (JWST Advanced Deep Extragalactic Survey), the astronomers determined that this galaxy experienced a short and intense period of star formation over a period between 30 and 90 million years. But between 10 and 20 million years before the point in time where it was observed with Webb, star formation suddenly stopped.

"Everything seems to happen faster and more dramatically in the early universe, and that might include galaxies moving from a star-forming phase to dormant or quenched," said Looser.

Astronomers have previously observed dead galaxies in the early universe, but this galaxy is the oldest yet -- just 700 million years after the big bang, more than 13 billion years ago. This observation is one of the deepest yet made with Webb.

In addition to the oldest, this galaxy is also relatively low mass -- about the same as the Small Magellanic Cloud (SMC), a dwarf galaxy near the Milky Way, although the SMC is still forming new stars. Other quenched galaxies in the early universe have been far more massive, but Webb's improved sensitivity allows smaller and fainter galaxies to be observed and analysed.

The astronomers say that although it appears dead at the time of observation, it's possible that in the roughly 13 billion years since, this galaxy may have come back to life and started forming new stars again.

"We're looking for other galaxies like this one in the early universe, which will help us place some constraints on how and why galaxies stop forming new stars," said D'Eugenio. "It could be the case that galaxies in the early universe 'die' and then burst back to life -- we'll need more observations to help us figure that out."

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Synthetic gene helps explain the mysteries of transcription across species

"Random DNA" is naturally active in the one-celled fungi yeast, while such DNA is turned off as its natural state in mammalian cells, despite their having a common ancestor a billion years ago and the same basic molecular machinery, a new study finds.

The new finding revolves around the process by which DNA genetic instructions are converted first into a related material called RNA and then into proteins that make up the body's structures and signals. In yeast, mice, and humans, the first step in a gene's expression, transcription, proceeds as DNA molecular "letters" (nucleobases) are read in one direction. While 80% of the human genome -- the complete set of DNA in our cells -- is actively decoded into RNA, less than 2% actually codes for genes that direct the building of proteins.

A longstanding mystery in genomics then is what is all this non-gene-related transcription accomplishing. Is it just noise, a side effect of evolution, or does it have functions?

A research team at NYU Langone Health sought to answer the question by creating a large, synthetic gene, with its DNA code in reverse order from its natural parent. Then they put synthetic gene into yeast and mouse stem cells and watched transcription levels in each. Published online March 6 in the journal Nature, the new study reveals that in yeast the genetic system is set so that nearly all genes are continually transcribed, while the same "default state" in the mammalian cells is that transcription is turned off.

Interestingly, say the study authors, the reverse order of the code meant that all of the mechanisms that evolved in yeast and mammalian cells to turn transcription on or off were absent because the reversed code was nonsense. Like a mirror image, however, the reversed code reflected some basic patterns seen in the natural code in terms of how often DNA letters were present, what they fell near, and how often they were repeated. With the reversed code being 100,000 molecular letters long, the team found that it randomly included many small stretches of previously unknown code that likely started transcription much more often yeast, and stopped it in mammalian cells.

"Understanding default transcription differences across species will help us to better understand what parts of the genetic code have functions, and which are accidents of evolution," said corresponding author Jef Boeke, PhD, the Sol and Judith Bergstein Director of the Institute for Systems Genetics at NYU Langone Health. "This in turn promises to guide the engineering of yeast to make new medicines, or create new gene therapies, or even to help us find new genes buried in the vast code."

The work lends weight to the theory that yeast's very active transcriptional state is set so that foreign DNA, rarely injected into yeast for instance by a virus as it copies itself, is likely to get transcribed into RNA. If that RNA builds a protein with a helpful function, the code will be preserved by evolution as a new gene. Unlike a single-celled organism in yeast, which can afford risky new genes that drive faster evolution, mammalian cells, as part of bodies with millions of cooperating cells, are less free to incorporate new DNA every time a cell encounters a virus. Many regulatory mechanisms protect the delicately balanced code as it is.

Big DNA

The new study had to account for the size of DNA chains, with 3 billion "letters" included in the human genome, and some genes being 2 million letters long. While famous techniques enable changes to be made letter by letter, some engineering tasks are more efficient if researchers build DNA from scratch, with far-flung changes made in large swaths of pre-assembled code swapped into a cell in place of its natural counterpart. Because human genes are so complex, Boeke's lab first developed its "genome writing" approach in yeast, but then recently adapted it to the mammalian genetic code. The study authors use yeast cells to assemble long DNA sequences in a single step, and then deliver the them into mouse embryonic stem cells.

For the current study, the research team addressed the question on how pervasive transcription is across evolution by introducing a synthetic 101 kilobase stretch of engineered DNA -- the human gene hypoxanthine phosphoribosyl transferase 1 (HPRT1) in reverse coding order. They observed widespread activity of the gene in yeast despite the lack in the nonsense code of promoters, DNA snippets that evolved to signal for the start of transcription.

Further, the team identified small sequences in the reversed code, repeated stretches of adenosine and thymine building blocks, known to be recognized by transcription factors, proteins that bind to DNA to initiate transcription. Just 5 to 15 letters long, such sequences could easily occur randomly and may partly explain the very active yeast default state, the authors said.

To the contrary, the same reversed code, inserted into the genome of a mouse embryonic stem cells, did not cause widespread transcription. In this scenario, transcription was repressed even though evolved CpG dinucleotides, known to actively shut down (silence) genes, were not functional in the reversed code. The team surmises that other basic elements in the mammalian genome may restrict transcription much more so than in yeast, and perhaps by directly recruiting a protein group (the polycomb complex) known to silence genes.

"The closer we get to introducing a 'genome's worth' of nonsense DNA into living cells, the better they can compare it to the actual, evolved genome," said first author Brendan Camellato, a graduate student in Boeke's lab. "This could lead us to a new frontier of engineered cell therapies, as the capacity to put in ever longer synthetic DNAs enables better understanding of what insertions genomes will tolerate, and perhaps the inclusion of one or more larger, complete, engineered genes."

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Invasive plant time bombs: A hidden ecological threat

Invasive plants can stay dormant for decades or even centuries after they have been introduced into an environment before rapidly expanding and wreaking ecological havoc, according to a new study led by the University of California, Davis.

The research, published in Nature Ecology and Evolution, looked at more than 5,700 species of invasive plants in nine regions around the globe. It represents the most comprehensive analysis of plant invasions conducted to date, said senior author Mohsen Mesgaran, an assistant professor in the Department of Plant Sciences at UC Davis.

"The longer it is dormant, we're more likely to ignore it," Mesgaran said. "This latency allows them to be overlooked, contributing to their eventual emergence as a serious invasive threat. They're like invasive time bombs."

Long periods of dormancy

The international team found that nearly one-third of the invasive plants they analyzed exhibited lag periods between introduction and rapid expansion, with the average time being 40 years. The longest dormant period -- sycamore maples in the United Kingdom -- was 320 years.

Consider the common lawn weed Plantago lanceolata, otherwise known as ribwort or buckhorn plantain, which has the longest dormancy in the United States, according to the report. Noxious to livestock and native plants, the plant was introduced in the United States in 1822 and is found widely here. Velvetleaf, which was introduced as a possible fiber crop, can be dormant for 50 years before it expands, threatening corn, soybean and other crops as it sucks up water and nutrients.

Nonnative species are generally introduced in two ways: by accident or through intentional importation for medicinal, ornamental, agricultural and other purposes. In California, about 65% of invasive plants were knowingly introduced.

"This lag phase may have played a role," Mesgaran said. "They didn't know. With an increase in trade and transportation and tourism we're going to have more problems."

Global herbaria

The researchers generated a list of invasive plants in Australia, Great Britain, Ireland, Japan, New Zealand, Madagascar, South Africa, Japan and the United States and used herbaria records, which are digitized and accessible online, to obtain global data on the location and time of species observations.

They then looked at trends to determine whether species exhibited dormant phases and, if so, for how long. A time series analysis was applied to detect lag periods, followed by a second analysis that compared climate during dormant and expansion phases.

In some of the species that invaded different regions, dormancy periods varied by location. In 90% of cases, climate conditions were different during times when the species spread, suggesting the plants waited for the right conditions or adapted to survive to an environment that was once unsuitable, Mesgaran said.

Planning for the future

Knowing that problems could loom in the future is key to managing pests and preventing widespread invasion and economic losses down the road. That means growers, policymakers and others should consider dormancy periods.

"The problem is most of the models that we have for risk assessment to see if the species are going to be invasive and a pest problem in the future don't account for this lag phase or this dormant phase," Mesgaran said. "It's not that they're not going to be a problem, it's just the calm before the storm."

The next steps in the research will be to examine the native climate of invasive species relative to conditions in these newer locations.

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Modeling the origins of life: New evidence for an 'RNA World'

Charles Darwin described evolution as "descent with modification." Genetic information in the form of DNA sequences is copied and passed down from one generation to the next. But this process must also be somewhat flexible, allowing slight variations of genes to arise over time and introduce new traits into the population.

But how did all of this begin? In the origins of life, long before cells and proteins and DNA, could a similar sort of evolution have taken place on a simpler scale? Scientists in the 1960s, including Salk Fellow Leslie Orgel, proposed that life began with the "RNA World," a hypothetical era in which small, stringy RNA molecules ruled the early Earth and established the dynamics of Darwinian evolution.

New research at the Salk Institute now provides fresh insights on the origins of life, presenting compelling evidence supporting the RNA World hypothesis. The study, published in Proceedings of the National Academy of Sciences (PNAS) on March 4, 2024, unveils an RNA enzyme that can make accurate copies of other functional RNA strands, while also allowing new variants of the molecule to emerge over time. These remarkable capabilities suggest the earliest forms of evolution may have occurred on a molecular scale in RNA.

The findings also bring scientists one step closer to re-creating RNA-based life in the laboratory. By modeling these primitive environments in the lab, scientists can directly test hypotheses about how life may have started on Earth, or even other planets.

"We're chasing the dawn of evolution," says senior author and Salk President Gerald Joyce. "By revealing these novel capabilities of RNA, we're uncovering the potential origins of life itself, and how simple molecules could have paved the way for the complexity and diversity of life we see today."

Scientists can use DNA to trace the history of evolution from modern plants and animals all the way back to the earliest single-celled organisms. But what came before that remains unclear. Double-stranded DNA helices are great for storing genetic information. Many of those genes ultimately code for proteins -- complex molecular machines that carry out all sorts of functions to keep cells alive. What makes RNA unique is that these molecules can do a bit of both. They're made of extended nucleotide sequences, similar to DNA, but they can also act as enzymes to facilitate reactions, much like proteins. So, is it possible that RNA served as the precursor to life as we know it?

Scientists like Joyce have been exploring this idea for years, with a particular focus on RNA polymerase ribozymes -- RNA molecules that can make copies of other RNA strands. Over the last decade, Joyce and his team have been developing RNA polymerase ribozymes in the lab, using a form of directed evolution to produce new versions capable of replicating larger molecules. But most have come with a fatal flaw: they aren't able to copy the sequences with a high enough accuracy. Over many generations, so many errors are introduced into the sequence that the resulting RNA strands no longer resemble the original sequence and have lost their function entirely.

Until now. The latest RNA polymerase ribozyme developed in the lab includes a number of crucial mutations that allow it to copy a strand of RNA with much higher accuracy.

In these experiments, the RNA strand being copied is a "hammerhead," a small molecule that cleaves other RNA molecules into pieces. The researchers were surprised to find that not only did the RNA polymerase ribozyme accurately replicate functional hammerheads, but over time, new variations of the hammerheads began to emerge. These new variants performed similarly, but their mutations made them easier to replicate, which increased their evolutionary fitness and led them to eventually dominate the lab's hammerhead population.

"We've long wondered how simple life was at its beginning and when it gained the ability to start improving itself," says first author Nikolaos Papastavrou, a research associate in Joyce's lab. "This study suggests the dawn of evolution could have been very early and very simple. Something at the level of individual molecules could sustain Darwinian evolution, and that might have been the spark that allowed life to become more complex, going from molecules to cells to multicellular organisms."

The findings highlight the critical importance of replication fidelity in making evolution possible. The RNA polymerase's copying accuracy must exceed a critical threshold to maintain heritable information over multiple generations, and this threshold would have risen as the evolving RNAs increased in size and complexity.

Joyce's team is re-creating this processin laboratory test tubes, applying increasing selective pressure on the system to produce better-performing polymerases, with the goal of one day producing an RNA polymerase that can replicate itself. This would mark the beginnings of autonomous RNA life in the laboratory, which the researchers say could be accomplished within the next decade.

The scientists are also interested in what else might occur once this mini "RNA World" has gained more autonomy.

"We've seen that selection pressure can improve RNAs with an existing function, but if we let the system evolve for longer with larger populations of RNA molecules, can new functions be invented?" says co-author David Horning, a staff scientist in Joyce's lab. "We're excited to answer how early life could ratchet up its own complexity, using the tools developed here at Salk."

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Juno spacecraft measures oxygen production on Jupiter's moon, Europa

NASA's Juno spacecraft has directly measured charged oxygen and hydrogen molecules from the atmosphere of one of Jupiter's largest moons, Europa. According to a new study co-authored by SwRI scientists and led by Princeton University, these observations provide key constraints on the potential oxygenation of its subsurface ocean.

"These findings have direct implications on the potential habitability of Europa," said Juno Principal Investigator Dr. Scott Bolton of SwRI, a co-author of the study.

"This study provides the first direct in-situ measurement of water components existing in Europa's atmosphere, giving us a narrow range that could support habitability."

In 2022, Juno completed a flyby of Europa, coming as close as 352 kilometers to the moon.

The SwRI-developed Jovian Auroral Distributions Experiment (JADE) instrument aboard Juno detected significant amounts of charged molecular oxygen and hydrogen lost from the atmosphere.

"For the first time, we've been able to definitively detect hydrogen and oxygen with in-situ measurements and further confirm that Europa's atmosphere is made primarily of hydrogen and oxygen molecules," said SwRI Staff Scientist and co-author Dr. Robert Ebert.

The source of these molecules is thought to be water ice on Europa's surface.

Jupiter's rampant radiation breaks H2O's molecular bonds, leaving behind oxygen and hydrogen.

The heavier oxygen molecules remain more constrained to the surface, or near-surface atmosphere, while the lighter-weight hydrogen predominately escapes into the atmosphere and beyond.

Oxygen produced in the ice is either lost from the atmosphere and/or sequestered in the surface.

Oxygen retained in Europa's ice may work its way to its subsurface ocean as a possible source of metabolic energy.

"Europa's ice shell absorbs radiation, protecting the ocean underneath. This absorption also produces oxygen within the ice, so in a way, the ice shell acts as Europa's lung, providing a potential oxygen source for the ocean." said Princeton University Research Scholar Dr. Jamey Szalay, the study's lead author.

"We put narrow constraints on the total oxygen production at Europa currently at around 12 kg per second. Before Juno, previous estimates ranged from a few kg per second to over 1,000 kg per second. The findings unambiguously demonstrate oxygen is continuously produced in the surface, just a good bit lower than we expected."

"We designed JADE to measure the charged particles that create Jupiter's auroras," said SwRI Staff Scientist and co-author Dr. Frederic Allegrini.

"Flybys of Europa were not part of the primary Juno mission. JADE was designed to work in a high-radiation environment but not necessarily Europa's environment, which is constantly bombarded with high levels of radiation. Nonetheless, the instrument performed beautifully."

The new measurements contribute to a greater understanding of Europa and its environment, open the door for newer, more precise models.

The study's new estimation of how much oxygen is produced within Europa's surface, for instance, could inform future research related to its subsurface ocean and potential habitability.

As these observations provide the first charged particle composition measurements within Europa's vicinity, they provide an important new window into the moons' complex interaction with its environment.

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8 in 10 lizards could be at risk due to deforestation

In Colorado, people flock to the Rocky Mountains when the summer heat gets unbearable. Animals seek shelter too when temperatures become extreme, and forests serve as critical sanctuaries for small tree-dwelling animals like lizards.

In a new study published March 5 in the journal Nature Climate Change, scientists from the University of Colorado Boulder and Tel Aviv University in Israel revealed that deforestation combined with climate change could negatively impact 84% of North America's lizards by the end of the century. Nearly one in five could face population decline.

Unlike mammals that can maintain their body temperatures in a variety of ways -- sweating when it gets too hot and relying on warm fur when it gets too cold -- cold-blooded animals like lizards have limited strategies to thermoregulate. Tree-climbing lizards move around tree trunks to bask in the sun for warmth. When the ground gets too hot, they climb higher or move into the shade.

"What's really interesting about lizards is that they just need to be able to move a short distance around the tree trunk to get to a very different climate and habitat environment," said Keith Musselman, an assistant professor in the Department of Geography and CU Boulder's Institute of Arctic and Alpine Research. "These microhabitats are particularly important when we think about how we modify our natural environment and make conservation decisions."

Using computer simulations, the team showed that global warming can actually benefit lizards living in colder regions or at higher latitudes in North America. Warmer weather increases the animals' activity time, meaning they have more time to look for food or mates during the day. However, deforestation would largely reverse these positive effects by reducing opportunities for shade in hotter climates that help them cool down.

The team simulated lizard models for different climate regions across North America. They found that tree loss could decrease lizards' activity time by an average of 34% by the end of the century. Without trees, the animals would have to hide under rocks or in caves to avoid overheating. The impact would be especially prominent for species that already live in warmer regions, where future summers will become too warm for activity on the ground.

The team estimated that deforestation would accelerate population declines for 18% of lizards in North America.

"Our work provides new insights into the mechanisms by which deforestation may cause population declines in the face of climate change," said Ofir Levy, a zoologist and Musselman's collaborator at Tel Aviv University. "The decline in lizards can lead to a cascading effect as they are an important part of almost every ecological system."

Despite international pledges to halt deforestation, tree clearing continues to happen globally. From 2001 to 2022, about 459 million hectares, or 12%, of global tree cover disappeared.

"Deforestation is a worldwide problem, and our conclusions can help decision-makers on other continents in designing conservation and habitat restoration programs that consider climate change," said Omer Zlotnick, the paper's first author and a Ph.D. student at Tel Aviv University.

Lizard populations are already at risk because of climate change. In one study, scientists estimated that 54% of lizard populations in Mexico would go extinct by 2080 because of their inability to adapt to the rapidly warming planet.

Deforestation would further exacerbate the threat by taking away these animals' refuges.

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Fossil named 'Attenborough's strange bird' was the first in its kind without teeth

A new fossil, named "Attenborough's strange bird" after naturalist and documentarian Sir David Attenborough, is the first of its kind to evolve a toothless beak. It's from a branch of the bird family tree that went extinct in the mass extinction 66 million years ago, and this strange bird is another puzzle piece that helps explain why some birds -- and their fellow dinosaurs -- went extinct, and others survived to today.

No birds alive today have teeth. But that wasn't always the case -- many early fossil birds had beaks full of sharp, tiny teeth. In a paper in the journal Cretaceous Research, scientists have described a new species of fossil bird that was the first of its kind to evolve toothless-ness; its name, in honor of naturalist Sir David Attenborough, means "Attenborough's strange bird."

"It is a great honour to have one's name attached to a fossil, particularly one as spectacular and important as this. It seems the history of birds is more complex than we knew," says Sir David Attenborough.

All birds are dinosaurs, but not all dinosaurs fall into the specialized type of dinosaurs known as birds, sort of like how all squares are rectangles, but not all rectangles are squares. The newly described Imparavis attenboroughi is a bird, and therefore, also a dinosaur.

Imparavis attenboroughi was a member of a group of birds called enantiornithines, or "opposite birds," named for a feature in their shoulder joints that is "opposite" from what's seen in modern birds. Enantiornithines were once the most diverse group of birds, but they went extinct 66 million years ago following the meteor impact that killed most of the dinosaurs. Scientists are still working to figure out why the enantiornithines went extinct and the ornithuromorphs, the group that gave rise to modern birds, survived.

"Enantiornithines are very weird. Most of them had teeth and still had clawed digits. If you were to go back in time 120 million years in northeastern China and walk around, you might have seen something that looked like a robin or a cardinal, but then it would open its mouth, and it would be filled with teeth, and it would raise its wing, and you would realize that it had little fingers," says Alex Clark, a PhD student at the University of Chicago and the Field Museum and the paper's corresponding author.

But "Attenborough's strange bird" bucked this trend. "Scientists previously thought that the first record of toothlessness in this group was about 72 million years ago, in the late Cretaceous. This little guy, Imparavis, pushes that back by about 48 to 50 million years. So toothlessness, or edentulism, evolved much earlier in this group than we thought," says Clark.

The specimen was found by an amateur fossil collector near the village of Toudaoyingzi in northeastern China and donated to the Shandong Tianyu Museum of Nature. Clark's advisor and co-author on the paper, Field Museum associate curator of fossil reptiles Jingmai O'Connor, first noticed something unusual about this fossil several years ago, when she was visiting the Shandong Tianyu Museum's collections.

"I think what drew me to the specimen wasn't its lack of teeth -- it was its forelimbs," says O'Connor. "It had a giant bicipital crest -- a bony process jutting out at the top of the upper arm bone, where muscles attach. I'd seen crests like that in Late Cretaceous birds, but not in the Early Cretaceous like this one. That's when I first suspected it might be a new species."

O'Connor, Clark, and their coauthors in China, Xiaoli Wang, Xiangyu Zhang, Xing Wang, Xiaoting Zheng, and Zhonghe Zhou, undertook further study of the specimen and determined that it did indeed represent an animal new to science.

The unusual wing bones could have allowed for muscle attachments that let this bird flap its wings with extra power. "We're potentially looking at really strong wing beats. Some features of the bones resemble those of modern birds like puffins or murres, which can flap crazy fast, or quails and pheasants, which are stout little birds but produce enough power to launch nearly vertically at a moment's notice when threatened," says Clark.

Meanwhile, the bird's toothless beak doesn't necessarily tell scientists what it was eating, since modern toothless birds have a wide variety of diets. Like its fellow enantiornithines, and unlike modern birds, it does not appear to have a digestive organ called a gizzard, or gastric mill, that helped it crush up its food.

While Clark notes that "an animal is more than the sum of its parts, and we can't fully know what an animal's life was like just by looking at single components of its body," he and his coauthors have been able to hypothesize about some of Imparavis's behavior and ecology, based on the details of its wings, feet, and beak together. "I like to think of these guys kind of acting like modern robins. They can perch in trees just fine, but for the most part, you see them foraging on the ground, hopping around and walking," says Clark.

"It seems like most enantiornithines were pretty arboreal, but the differences in the forelimb structure of Imparavis suggests that even though it's still probably lived in the trees, it maybe ventured down to the ground to feed, and that might mean it had a unique diet compared to other enantiornithines, which also might explain why it lost its teeth," says O'Connor.

In the paper, the researchers also revisited a previously described fossil bird, Chiappeavis (which O'Connor named eight years ago after her PhD advisor), and suggest that it too was an early toothless enantiornithine. This finding, along with Imparavis, indicates that toothlessness may not have been quite as unique in Early Cretaceous enantiornithines as previously thought.

Clark said that nature documentaries by Sir David Attenborough, in which the renowned British naturalist narrates the behavior of different animals, were pivotal to his own interest in science. "I most likely wouldn't be in the natural sciences if it weren't for David Attenborough's documentaries," says Clark, explaining why he chose to name the new fossil after Attenborough.

Clark and O'Connor noted the importance of Attenborough's messaging that not only celebrates life on earth, but also warns against the mass extinction the planet is undergoing due to human-caused climate change and habitat destruction.

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Fossils of giant sea lizard with dagger-like teeth show how our oceans have fundamentally changed since the dinosaur era

Paleontologists have discovered a strange new species of marine lizard with dagger-like teeth that lived near the end of the age of dinosaurs. Their findings, published in Cretaceous Research, show a dramatically different ocean ecosystem to what we see today, with numerous giant top predators eating large prey, unlike modern ecosystems where a few apex predators -- such as great white sharks, orca and leopard seals -- dominate.

Khinjaria acuta was a member of the family Mosasauridae, or mosasaurs. Mosasaurs weren't dinosaurs, but giant marine lizards, relatives of today's Komodo dragons and anacondas, which ruled the oceans 66 million years ago, during the era of Tyrannosaurus and Triceratops.

Khinjaria had powerful jaws and long, dagger-like teeth to seize prey, giving it a nightmarish appearance. It was part of an extraordinarily diverse fauna of predators that inhabited the Atlantic Ocean off the coast of Morocco, just before the dinosaurs went extinct.

The study is based on a skull and parts of the skeleton collected from a phosphate mine southeast of Casablanca. The study involved researchers from the University of Bath in the UK, the Marrakech Museum of Natural History, the Museum National d' Histoire Naturelle (NMNH) in Paris (France), Southern Methodist University in Texas (USA), and the University of the Basque Country (Bilbao).

"What's remarkable here is the sheer diversity of top predators," said Dr Nick Longrich of the Department of Life Sciences and the Milner Centre for Evolution at the University of Bath, who led the study. "We have multiple species growing larger than a great white shark, and they're top predators, but they all have different teeth, suggesting they're hunting in different ways.

"Some mosasaurs had teeth to pierce prey, others to cut, tear, or crush. Now we have Khinjaria, with a short face full of huge, dagger-shaped teeth. This is one of the most diverse marine faunas seen anywhere, at any time in history, and it existed just before the marine reptiles and the dinosaurs went extinct."

Morocco's diverse marine reptiles lived just before an asteroid struck the Yucatan Peninsula in Mexico. Dust and fine particles shot into the high atmosphere blocked out the sun for months, causing darkness and cooling, which drove most of the planet's species to extinction.

Dinosaurs were wiped out on land, and a handful of surviving species of mammals, birds, and lizards diversified to take their place. Meanwhile, the same happened in the oceans.

Mosasaurs, plesiosaurs and giant sea turtles disappeared, along with entire families of fish. This opened the way for whales and seals, and fish like swordfish and tuna appeared. However, the ecosystem that evolved after the impact was different.

"There seems to have been a huge change in the ecosystem structure in the past 66 million years," said Longrich. "This incredible diversity of top predators in the Late Cretaceous is unusual, and we don't see that in modern marine communities."

Modern marine food chains have just a few large apex predators, animals like orcas, white sharks, and leopard seals. The Cretaceous had a whole host of top predators.

Dr Longrich said: "It's not just that we're getting rid of the old actors and recasting new ones into the same roles. The story has changed dramatically.

"Modern ecosystems have predators like baleen whales and dolphins that eat small prey, and not many things eating large prey. The Cretaceous has a huge number of marine reptile species that take large prey. Whether there's something about marine reptiles that caused the ecosystem to be different, or the prey, or perhaps the environment, we don't know. But this was an incredibly dangerous time to be a fish, a sea turtle, or even a marine reptile."

Professor Nathalie Bardet, from the NMNH, said: "The Phosphates of Morocco deposit in a shallow and warm epicontinental sea, under a system of upwellings; these zones are caused by currents of deep, cold, nutrient-rich waters rising towards the surface, providing food for large numbers of sea creatures and, as a result, supporting a lot of predators. This is probably one of the explanations for this extraordinary paleobiodiversity observed in Morocco at the end of the Cretaceous."

"The phosphates of Morocco immerse us in the Upper Cretaceous seas during the latest geological times of the dinosaurs' age. No deposit has provided so many fossils and so many species from this period," said Professor NE. Jalil of NMNH. "After the' titan of the seas', Thalassotitan, the 'saw-toothed' mosasaur Xenodens, the 'star-toothed' mosasaur, Stelladens and many others, now there is Khinjaria, a new mosasaur with dagger-like teeth.

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Webb unlocks secrets of one of the most distant galaxies ever seen

Looking deeply into space and time, two teams using NASA's James Webb Space Telescope have studied the exceptionally luminous galaxy GN-z11, which existed when our 13.8 billion-year-old universe was only about 430 million years old.

Initially detected with NASA's Hubble Space Telescope, this galaxy -- one of the youngest and most distant ever observed -- is so bright that it is challenging scientists to understand why. Now, GN-z11 is giving up some of its secrets.

Vigorous Black Hole Is Most Distant Ever Found

A team studying GN-z11 with Webb found the first clear evidence that the galaxy is hosting a central, supermassive black hole that is rapidly accreting matter. Their finding makes this the farthest active supermassive black hole spotted to date.

"We found extremely dense gas that is common in the vicinity of supermassive black holes accreting gas," explained principal investigator Roberto Maiolino of the Cavendish Laboratory and the Kavli Institute of Cosmology at the University of Cambridge in the United Kingdom. "These were the first clear signatures that GN-z11 is hosting a black hole that is gobbling matter."

Using Webb, the team also found indications of ionized chemical elements typically observed near accreting supermassive black holes. Additionally, they discovered a very powerful wind being expelled by the galaxy. Such high-velocity winds are typically driven by processes associated with vigorously accreting supermassive black holes.

"Webb's NIRCam (Near-Infrared Camera) has revealed an extended component, tracing the host galaxy, and a central, compact source whose colors are consistent with those of an accretion disk surrounding a black hole," said investigator Hannah Übler, also of the Cavendish Laboratory and the Kavli Institute.

Together, this evidence shows that GN-z11 hosts a 2-million-solar-mass, supermassive black hole in a very active phase of consuming matter, which is why it's so luminous.

Pristine Gas Clump in GN-z11's Halo Intrigues Researchers

A second team, also led by Maiolino, used Webb's NIRSpec (Near-Infrared Spectrograph) to find a gaseous clump of helium in the halo surrounding GN-z11.

"The fact that we don't see anything else beyond helium suggests that this clump must be fairly pristine," said Maiolino. "This is something that was expected by theory and simulations in the vicinity of particularly massive galaxies from these epochs -- that there should be pockets of pristine gas surviving in the halo, and these may collapse and form Population III star clusters."

Finding the never-before-seen Population III stars -- the first generation of stars formed almost entirely from hydrogen and helium -- is one of the most important goals of modern astrophysics. These stars are anticipated to be very massive, very luminous, and very hot. Their expected signature is the presence of ionized helium and the absence of chemical elements heavier than helium.

The formation of the first stars and galaxies marks a fundamental shift in cosmic history, during which the universe evolved from a dark and relatively simple state into the highly structured and complex environment we see today.

In future Webb observations, Maiolino, Übler, and their team will explore GN-z11 in greater depth, and they hope to strengthen the case for the Population III stars that may be forming in its halo.

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Arctic could become 'ice-free' within a decade

The Arctic could see summer days with practically no sea ice as early as the next couple of years, according to a new study out of the University of Colorado Boulder.

The findings, published March 5 in the journal Nature Reviews Earth & Environment, suggest that the first ice-free day in the Arctic could occur over 10 years earlier than previous projections, which focused on when the region would be ice-free for a month or more. The trend remains consistent under all future emission scenarios.

By mid-century, the Arctic is likely to see an entire month without floating ice during September, when the region's sea ice coverage is at its minimum. At the end of the century, the ice-free season could last several months a year, depending on future emissions scenarios. For example, under a high-emissions, or business-as-usual, scenario, the planet's northernmost region could become consistently ice-free even in some winter months.

For scientists, an ice-free Arctic doesn't mean there would be zero ice in the water.

Instead, researchers say the Arctic is ice-free when the ocean has less than 1 million square kilometers (386,000 square miles) of ice. The threshold represents less than 20% of what the region's seasonal minimum ice cover was in the 1980s. In recent years, the Arctic Ocean had around 3.3 million square kilometers of sea ice area at its minimum in September.

Alexandra Jahn, associate professor of atmospheric and oceanic sciences and fellow at CU Boulder's Institute of Arctic and Alpine Research, set out to analyze existing literature on sea ice projections. She and her collaborators also analyzed sea ice coverage data from computational climate models to assess how the Arctic might change daily in the future.

They found that the first day when sea ice coverage dips below the 1-square-kilometer threshold would occur on average four years earlier than the monthly averages, but could occur up to 18 years earlier.

"When it comes to communicating what scientists expect to happen in the Arctic, it is important to predict when we might observe the first ice-free conditions in the Arctic, which will show up in the daily satellite data," Jahn said.

The team projected the Arctic Ocean could become ice-free for the first time on a late August or early September day between the 2020s to 2030s under all emissions scenarios.

Jahn said greenhouse gas emissions are the main contributors to sea ice loss. A decrease in snow and ice cover increases the amount of heat from sunlight absorbed by the ocean, exacerbating ice melt and warming in the Arctic.

Sea ice declines have significant impacts on Arctic animals that rely on sea ice for survival, including seals and polar bears. In addition, as the ocean warms up, researchers are concerned that non-native fish could move into the Arctic Ocean. The impact of these invasive species on local ecosystems remains unclear.

Sea ice loss also poses a risk to the communities living near the coastal region. Sea ice plays a significant role in buffering the impacts of ocean waves on the coastal land, Jahn said. As sea ice retreats, ocean waves would get bigger, causing coastal erosion.

While an ice-free Arctic is inevitable, Jahn said future emissions levels will still determine how often the conditions occur. Under an intermediate emissions scenario, a path the current society is on, the Arctic might become ice-free only during late summer and early fall from August to October. But under the highest emissions scenario, the Arctic could be ice-free for up to nine months by late this century.

"This would transform the Arctic into a completely different environment, from a white summer Arctic to a blue Arctic. So even if ice-free conditions are unavoidable, we still need to keep our emissions as low as possible to avoid prolonged ice-free conditions," Jahn said.

The good news: Arctic sea ice is resilient and can return quickly if the atmosphere cools down.

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Humans have driven the Earth's freshwater cycle out of its stable state

A new analysis of freshwater resources across the globe shows that human activity has pushed variation in the planet's freshwater cycle well outside of its pre-industrial range. The study shows that the updated planetary boundary for freshwater change was surpassed by the mid-twentieth century. In other words, for the past century, humans have been pushing the Earth's freshwater system far beyond the stable conditions that prevailed before industrialization.

This is the first time that global water cycle change has been assessed over such a long timescale with an appropriate reference baseline.

The findings, published in Nature Water, show that human pressures, such as dam construction, large-scale irrigation and global warming, have altered freshwater resources to such an extent that their capacity to regulate vital ecological and climatic processes is at risk.

The international research team calculated monthly streamflow and soil moisture at a spatial resolution of roughly 50x50 kilometers using data from hydrological models that combine all major human impacts on the freshwater cycle.

As a baseline, they determined the conditions during the pre-industrial period (1661-1860). They then compared the industrial period (1861-2005) against this baseline.

Their analysis revealed an increase in the frequency of exceptionally dry or wet conditions -deviations in streamflow and soil moisture.

Dry and wet deviations have consistently occurred over substantially larger areas since the early 20th century than during the pre-industrial period.

Overall, the global land area experiencing deviations has nearly doubled compared with pre-industrial conditions.

'We found that exceptional conditions are now much more frequent and widespread than before, clearly demonstrating how human actions have changed the state of the global freshwater cycle', says Vili Virkki, a doctoral researcher at Aalto University and one of the lead authors of the paper.

Because the analysis was done at a high spatial and temporal resolution, the researchers could explore geographical differences in the deviations.

Exceptionally dry streamflow and soil moisture conditions became more frequent in many tropical and subtropical regions, while many boreal and temperate regions saw an increase in exceptionally wet conditions, especially in terms of soil moisture.

These patterns match changes seen in water availability due to climate change.

There were more complex patterns in many regions with a long history of human land use and agriculture.

For example, the Nile, Indus and Mississippi river basins have experienced exceptionally dry streamflow and wet soil moisture conditions, indicating changes driven by irrigation.

'Using a method that's consistent and comparable across hydrological variables and geographical scales is crucial for understanding the biophysical processes and human actions that drive the changes we're seeing in freshwater,' explains Miina Porkka, who co-led the study at Aalto before moving to the University of Eastern Finland.

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Researchers invent new triple-junction tandem solar cells with world-record efficiency

Scientists from the National University of Singapore (NUS) have developed a novel triple-junction perovskite/Si tandem solar cell that can achieve a certified world-record power conversion efficiency of 27.1 per cent across a solar energy absorption area of 1 sq cm, representing the best-performing triple-junction perovskite/Si tandem solar cell thus far. To achieve this, the team engineered a new cyanate-integrated perovskite solar cell that is stable and energy efficient.

Solar cells can be fabricated in more than two layers and assembled to form multi-junction solar cells to increase efficiency. Each layer is made of different photovoltaic materials and absorbs solar energy within a different range. However, current multi-junction solar cell technologies pose many issues, such as energy loss which leads to low voltage and instability of the device during operation.

To overcome these challenges, Assistant Professor Hou Yi led a team of scientists from NUS College of Design and Engineering (CDE) and Solar Energy Research Institute of Singapore (SERIS) to demonstrate, for the first time, the successful integration of cyanate into a perovskite solar cell to develop a cutting-edge triple-junction perovskite/Si tandem solar cell that surpasses the performance of other similar multi-junction solar cells. Asst Prof Hou is a Presidential Young Professor at the Department of Chemical and Biomolecular Engineering under CDE as well as a Group Leader at SERIS, a university-level research institute in NUS.

"Remarkably, after 15 years of ongoing research in the field of perovskite-based solar cells, this work constitutes the first experimental evidence for the inclusion of cyanate into perovskites to boost the stability of its structure and improve power conversion efficiency," said Asst Prof Hou.

The experimental process that led to this ground-breaking discovery was published in Nature on 4 March 2024.

Fabricating energy-efficient solar cell technology

The interactions between the components of the perovskite structure determine the energy range that it can reach. Adjusting the proportion of these components or finding a direct substitute can help modify the perovskite's energy range. However, prior research has yet to produce a perovskite recipe with an ultrawide energy range and high efficiency.

In this recently published work, the NUS team experimented on cyanate, a novel pseudohalide, as a substitute for bromide -- an ion from the halide group that is commonly used in perovskites. Dr Liu Shunchang, Research Fellow in Asst Prof Hou's team, employed various analytical methods to confirm the successful integration of cyanate into the perovskite structure, and fabricated a cyanate-integrated perovskite solar cell.

Further analysis of the new perovskite's atomic structure provided -- for the first time -- experimental evidence that incorporating cyanate helped to stabilise its structure and form key interactions within the perovskite, demonstrating how it is a viable substitute for halides in perovskite-based solar cells.

When assessing performance, the NUS scientists found that perovskite solar cells incorporated with cyanate can achieve a higher voltage of 1.422 volts compared to 1.357 volts for conventional perovskite solar cells, with a significant reduction in energy loss.

The researchers also tested the newly engineered perovskite solar cell by continuously operating it at maximum power for 300 hours under controlled conditions. After the test period, the solar cell remained stable and functioned above 96 per cent capacity.

Encouraged by the impressive performance of the cyanate-integrated perovskite solar cells, the NUS team took their ground-breaking discovery to the next step by using it to assemble a triple-junction perovskite/Si tandem solar cell. The researchers stacked a perovskite solar cell and a silicon solar cell to create a dual-junction half-cell, providing an ideal base for the attachment of the cyanate-integrated perovskite solar cell.

Once assembled, the researchers demonstrated that despite the complexity of the triple-junction perovskite/Si tandem solar cell structure, it remained stable and attained a certified world-record efficiency of 27.1 per cent from an accredited independent photovoltaic calibration laboratory.

"Collectively, these advancements offer ground-breaking insights into mitigating energy loss in perovskite solar cells and set a new course for the further development of perovskite-based triple junction solar technology," said Asst Prof Hou.

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Astronomers reveal a new link between water and planet formation

Researchers have found water vapour in the disc around a young star exactly where planets may be forming. Water is a key ingredient for life on Earth, and is also thought to play a significant role in planet formation. Yet, until now, we had never been able to map how water is distributed in a stable, cool disc -- the type of disc that offers the most favourable conditions for planets to form around stars. The new findings were made possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner.

"I had never imagined that we could capture an image of oceans of water vapour in the same region where a planet is likely forming," says Stefano Facchini, an astronomer at the University of Milan, Italy, who led the study published today in Nature Astronomy. The observations reveal at least three times as much water as in all of Earth's oceans in the inner disc of the young Sun-like star HL Tauri, located 450 light-years away from Earth in the constellation Taurus.

"It is truly remarkable that we can not only detect but also capture detailed images and spatially resolve water vapour at a distance of 450 light-years from us ," adds co-author Leonardo Testi, an astronomer at the University of Bologna, Italy. The 'spatially resolved' observations with ALMA allow astronomers to determine the distribution of water in different regions of the disc. "Taking part in such an important discovery in the iconic HL Tauri disc was beyond what I had ever expected for my first research experience in astronomy," adds Mathieu Vander Donckt from the University of Liege, Belgium, who was a master's student when he participated in the research.

A significant amount of water was found in the region where a known gap in the HL Tauri disc exists. Ring-shaped gaps are carved out in gas- and dust-rich discs by orbiting young planet-like bodies as they gather up material and grow. "Our recent images reveal a substantial quantity of water vapour at a range of distances from the star that include a gap where a planet could potentially be forming at the present time," says Facchini. This suggests that this water vapour could affect the chemical composition of planets forming in those regions.

Observing water with a ground-based telescope is no mean feat as the abundant water vapour in Earth's atmosphere degrades the astronomical signals. ALMA, operated by ESO together with its international partners, is an array of telescopes in the Chilean Atacama Desert at about 5000 metres elevation that was built in a high and dry environment specifically to minimise this degradation, providing exceptional observing conditions. "To date, ALMA is the only facility able to spatially resolve water in a cool planet-forming disc," says co-author Wouter Vlemmings, a professor at the Chalmers University of Technology in Sweden.*

"It is truly exciting to directly witness, in a picture, water molecules being released from icy dust particles," says Elizabeth Humphreys, an astronomer at ESO who also participated in the study. The dust grains that make up a disc are the seeds of planet formation, colliding and clumping into ever larger bodies orbiting the star. Astronomers believe that where it is cold enough for water to freeze onto dust particles, things stick together more efficiently -- an ideal spot for planet formation. "Our results show how the presence of water may influence the development of a planetary system, just like it did some 4.5 billion years ago in our own Solar System," Facchini adds.

With upgrades happening at ALMA and ESO's Extremely Large Telescope (ELT) coming online within the decade, planet formation and the role water plays in it will become clearer than ever. In particular METIS, the Mid-infrared ELT Imager and Spectrograph, will give astronomers unrivalled views of the inner regions of planet-forming discs, where planets like Earth form.

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Scientists propose new method for tracking elusive origins of CO2 emissions from streams

A team of researchers from the University of Massachusetts Amherst that specializes in accounting for the carbon dioxide release by streams, rivers and lakes recently demonstrated that the chemical process known as "carbonate buffering" can account for the majority of emissions in highly alkaline waters. Furthermore, carbonate buffering distorts the most commonly used method of tracking the origins of CO2 in streams. The research, published in Global Biogeochemical Cycles, proposes a better method for tracking the origin of riverine CO2 emissions.

Inland waters, including streams, rivers and lakes, account for roughly 5.5 gigatons of CO2 emissions annually -- about 15% of what humans emit.

But current climate models have trouble accounting for this carbon, in part because, says Matthew Winnick, assistant professor of Earth, Geographic and Climate Sciences at UMass Amherst and the paper's lead author, much of this carbon seems to be produced cryptically, through carbonate buffering.

"The process is a little weird," says Winnick. "It acts as a kind of hidden reserve pool of CO2, replenishing carbon that is lost to the atmosphere, and ultimately increasing the amount of CO2 available for off-gassing."

To show how this hidden pool operates, Winnick and his co-author, then-UMass graduate student Brian Saccardi, looked to studies that focused on the carbon content of the oceans.

"Carbonate buffering is a really well-known phenomenon in the ocean," says Winnick, "and even though oceans work differently from inland waters, we were able to borrow the geochemical equations to build a series of models that could account for a wide range of river and stream conditions."

So what is carbonate buffering? It begins with CO2 -- which is everywhere: in the air, in the soil and in water.

When CO2 dissolves in water, it can react to form carbonic acid, which, through further reactions, can then become bicarbonate and carbonate.

This reaction can also run in reverse, which means that high levels of bicarbonate and carbonate can act as reserve pools of CO2, driving emissions.

This entire balance of CO2, water and carbonate is called "carbonate buffering," and the carbonate reserves can be emitted as a greenhouse gas from stream systems.

Indeed, Winnick and Saccardi found that this hidden pool can account for more than 60% of CO2 emissions under alkaline conditions.

There's yet another trick that carbonate buffering has up its sleeve.

In the era of global warming, it is critically important to know both how much carbon is being emitted overall and where this carbon is coming from.

"While we don't think stream emissions contribute to global warming, there is a big question about whether these emissions will change as climate warms, which could amplify warming in the future. To predict changes, we need to know where the CO2 is coming from," says Winnick.

But figuring out which molecule of CO2 came from which source is not a simple task.

To track carbon, especially carbon emitted by bodies of water, scientists often use carbon isotopes, or versions of carbon with different masses, which act as a sort of forensic signature that can indicate the carbon's origin.

However, Winnick and Saccardi discovered that isotope signals in streams are highly sensitive to carbonate buffering reactions.

"The primary way we use isotopes to track sources is through their relationship with CO2 concentrations, but carbonate buffering causes these relationships to break down," says Winnick.

This breakdown can point to the wrong carbon culprit if not properly accounted for.

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Orcas demonstrating they no longer need to hunt in packs to take down the great white shark

An orca (killer whale) has been observed, for the first-ever time, individually consuming a great white shark -- and within just two minutes.

"The astonishing predation, off the coast of Mossel Bay, South Africa, represents unprecedented behavior underscoring the exceptional proficiency of the killer whale," remarks Dr. Alison Towner from Rhodes University, who led an international research team into the discovery.

Their findings are published today in the peer-reviewed African Journal of Marine Science.

The groundbreaking insight is the latest from Dr. Towner and the team, who, in 2022 in the same journal, revealed that a pair of orca were hunting and killing great white sharks off the coast of South Africa since 2017 -- managing to drive large numbers of the sharks from their natural aggregation sites.

Orcas are generally known to work together to catch large prey like sea lions, seals, and even other whales -- and of course, sharks too. By hunting together, they can surround prey and use their combined intelligence and strength to attack. They can hunt large animals individually. However, this is the first such occurrence on what is one of the world's largest predators -- the great white.

"Again, as previously in South Africa, the orcas are exhibiting a strong preference for extracting and consuming the lipid-rich livers of white sharks -- a specialized feeding behavior," explains Dr. Towner, who has studied great white sharks for the last 17 years, learning about their movement patterns through tagging data.

"But what we witnessed was an orca, nicknamed Starboard -- due to his collapsed dorsal fin -- performing alone to incapacitate and consume a white shark within an astounding two-minute timeframe.

"Starboard was observed preying on a 2.5-meter (8.2 feet) juvenile white shark, later carrying the shark's liver in its mouth past a boat.

"This sighting revealed evidence of solitary hunting by at least one killer whale, challenging conventional cooperative hunting behaviors known in the region.

"These are groundbreaking insights into the predatory behavior of this species, and our findings significantly contribute to the global understanding of Killer Whale predation dynamics, enhancing knowledge of marine ecosystems and predator-prey relationships."

During the observed interactions of this event, at least two white sharks were killed, as evidenced by the discovery of a second carcass measuring 3.55 meters (11.6 feet) nearby.

"The study raises critical questions about the impact of killer whale predation on shark populations in South Africa," Dr. Towner says. "The displacement of various shark species due to killer whale presence may have implications for mesopredator release and potential trophic changes in the marine ecosystem."

Understanding the ecological dynamics of killer whale predation is paramount for marine conservation efforts. The authors state that this event "underscores the urgent need for adaptable conservation strategies and vigilant ecological monitoring amidst changing environmental conditions."

Founding Director and Principal Scientist at Sea Search Research & Conservation, and at the Department of BotZoo, University of Stellenbosch, Dr. Simon Elwen, is an expert in the ecology, behavior, and conservation status of whales.

Commenting on the importance of Dr. Towner's team's findings, he says: "The observations reported here add more layers to the fascinating story of these two killer whales and their capabilities. As smart, top predators, killer whales can rapidly learn new hunting techniques on their own or from others, so monitoring and understanding the behaviors used here and by other killer whales in South Africa is an important part of helping us understand more about these animals."

The involvement of land-based observers, tourists on vessels, and collaborating institutions played a "pivotal role" in capturing this crucial data and footage of the predation events.

This particular event "underscores the benefits of citizen science as a collaborative effort between researchers, tourists, and organizations," the authors state.

Esther Jacobs, from the marine conservation initiative, Keep Fin Alive, recounts her experience witnessing the predation: "Upon reaching Mossel Bay's Seal Island, the scent of shark liver oil and a noticeable slick indicated a recent kill. Tracking Port and Starboard near the island, they remained separated.

"Witnessing a white shark's fin break the surface initially sparked excitement, but that turned to a somber realization as Starboard swiftly approached. The moment Starboard rapidly preyed on my favorite shark species was both devastating and intensely powerful."

Co-author Dr. Primo Micarelli, from the Shark Studies Centre and Siena University, was on board the vessel White Shark Africa and commented: "Over two decades of annual visits to South Africa, I've observed the profound impact these killer whales have on the local white shark population. Seeing Starboard carry a white shark's liver past our vessel is unforgettable.

"Despite my awe for these predators, I'm increasingly concerned about the coastal marine ecology balance."

Concluding, Dr. Towner highlights that the new findings on killer whales provide important further insights into how adaptable mammalian predators specialize and diverge ecologically.

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