Category: 7. Science

E+E Leader Team

Marine fish may be among the most overlooked contributors to the ocean’s carbon cycle. A new study led by researchers at the University of Miami offers the first direct evidence that fish living at mesopelagic depths—200 to 1,000 meters below the ocean surface—excrete biogenic carbonate, a key component of the marine inorganic carbon cycle.

Published in the Journal of Experimental Biology, the research focuses on the blackbelly rosefish (Helicolenus dactylopterus), a deep-sea species that survives capture and lab acclimation. Scientists found that this fish, residing at roughly 400 meters depth, produces intestinal carbonate at rates similar to those of shallow-water species, confirming a long-standing but untested assumption in ocean carbon modeling.

Fish Carbonate: A Deep Dive Into Ichthyocarbonate

Ichthyocarbonate—carbonate precipitated in the guts of marine fish as part of their osmoregulation—is critical for absorbing seawater and eliminating excess ions. These particles, expelled into the ocean, sink and dissolve, influencing both surface and deep ocean chemistry.

The study found that blackbelly rosefish excrete ichthyocarbonate at a rate of approximately 5 mg/kg/hour—consistent with predictions based on fish size and temperature. Their metabolic rates, however, were lower than anticipated, suggesting that even low-energy deep-sea fish may contribute more to global carbonate budgets than previously thought.

Summarized by Dr. Martin Grosell, Chair of Ichthyology at the University of Miami,

Our observations support assumptions of ichthyocarbonate excretion by mesopelagic fishes, and suggest that thermal and allometric relationships for shallow water species extend to deep populations.

Implications for the Global Carbon Cycle

Mesopelagic fishes make up an estimated 94% of global fish biomass. Until now, their contribution to carbonate production—let alone its composition, structure, and fate—had been largely speculative. With confirmation that fish at these depths produce and excrete carbonate similar in morphology and mineral content to shallow species, a major uncertainty in carbon cycle modeling has been addressed.

Notably:

• Composition: The carbonate was high-magnesium calcite and amorphous carbonate, matching those found in warmer, shallow species.
• Stability: The carbonate dissolved faster at cold temperatures, meaning more is likely to reach deeper ocean layers where long-term carbon sequestration occurs.
• Origin: Up to 52% of the carbonate’s carbon came from dietary sources, transporting organic carbon to deeper waters—a key part of the biological pump.

This discovery elevates the role of mesopelagic fish in transferring both inorganic and organic carbon from the surface to depths where it can be locked away for centuries.

Challenges and Next Steps

Capturing and studying deep-sea fish without compromising their physiology remains difficult. The blackbelly rosefish lacks a swim bladder, enabling successful retrieval and lab monitoring. But it’s a benthic (non-migratory) species, and most mesopelagic fish migrate vertically by hundreds of meters each day, likely increasing their carbonate production through elevated metabolic activity.

Future research is needed to:

• Measure ichthyocarbonate production in vertically migrating species
• Determine whether fish excrete carbonate at the shallow or deep end of their migrations
• Refine global carbon cycle models with these new insights

Why This Matters

Carbonate produced by marine organisms—including corals, plankton, and now fish—helps buffer ocean acidity, influence deep-sea alkalinity, and control how much CO₂ the ocean can store. This study shows that fish—often overlooked in climate models—are potentially major drivers of oceanic carbon dynamics, particularly at depth.

For climate scientists, oceanographers, and environmental modelers, incorporating this revised understanding of biogenic carbonate production into global carbon budgets could improve projections of carbon sequestration and ocean acidification resilience.

Outdoor lighting for buildings, roads and advertising can help people see in the dark of night, but many astronomers are growing increasingly concerned that these lights could be blinding us to the rest of the universe.

An estimate from 2023 showed that the rate of human-produced light is increasing in the night sky by as much as 10% per year.

I’m an astronomer who has chaired a standing commission on astronomical site protection for the International Astronomical Union-sponsored working groups studying ground-based light pollution.

My work with these groups has centered around the idea that lights from human activities are now affecting astronomical observatories on what used to be distant mountaintops.

Hot science in the cold, dark night

While orbiting telescopes like the Hubble Space Telescope or the James Webb Space Telescope give researchers a unique view of the cosmos – particularly because they can see light blocked by the Earth’s atmosphere – ground-based telescopes also continue to drive cutting-edge discovery.

Telescopes on the ground capture light with gigantic and precise focusing mirrors that can be 20 to 35 feet (6 to 10 meters) wide. Moving all astronomical observations to space to escape light pollution would not be possible, because space missions have a much greater cost and so many large ground-based telescopes are already in operation or under construction.

Around the world, there are 17 ground-based telescopes with primary mirrors as big or bigger than Webb’s 20-foot (6-meter) mirror, and three more under construction with mirrors planned to span 80 to 130 feet (24 to 40 meters).

The newest telescope starting its scientific mission right now, the Vera Rubin Observatory in Chile, has a mirror with a 28-foot diameter and a 3-gigapixel camera. One of its missions is to map the distribution of dark matter in the universe.

To do that, it will collect a sample of 2.6 billion galaxies. The typical galaxy in that sample is 100 times fainter than the natural glow in the nighttime air in the Earth’s atmosphere, so this Rubin Observatory program depends on near-total natural darkness.

Any light scattered at night – road lighting, building illumination, billboards – would add glare and noise to the scene, greatly reducing the number of galaxies Rubin can reliably measure in the same time, or greatly increasing the total exposure time required to get the same result.

The LED revolution

Astronomers care specifically about artificial light in the blue-green range of the electromagnetic spectrum, as that used to be the darkest part of the night sky. A decade ago, the most common outdoor lighting was from sodium vapor discharge lamps. They produced an orange-pink glow, which meant that they put out very little blue and green light.

Even observatories relatively close to growing urban areas had skies that were naturally dark in the blue and green part of the spectrum, enabling all kinds of new observations.

Then came the solid-state LED lighting revolution. Those lights put out a broad rainbow of color with very high efficiency – meaning they produce lots of light per watt of electricity. The earliest versions of LEDs put out a large fraction of their energy in the blue and green, but advancing technology now gets the same efficiency with “warmer” lights that have much less blue and green.

Nevertheless, the formerly pristine darkness of the night sky now has much more light, particularly in the blue and green, from LEDs in cities and towns, lighting roads, public spaces and advertising.

The broad output of color from LEDs affects the whole spectrum, from ultraviolet through deep red.

The U.S. Department of Energy commissioned a study in 2019 which predicted that the higher energy efficiency of LEDs would mean that the amount of power used for lights at night would go down, with the amount of light emitted staying roughly the same.

But satellites looking down at the Earth reveal that just isn’t the case. The amount of light is going steadily up, meaning that cities and businesses were willing to keep their electricity bills about the same as energy efficiency improved, and just get more light.

Natural darkness in retreat

As human activity spreads out over time, many of the remote areas that host observatories are becoming less remote. Light domes from large urban areas slightly brighten the dark sky at mountaintop observatories up to 200 miles (320 kilometers) away. When these urban areas are adjacent to an observatory, the addition to the skyglow is much stronger, making detection of the faintest galaxies and stars that much harder.

When the Mt. Wilson Observatory was constructed in the Angeles National Forest near Pasadena, California, in the early 1900s, it was a very dark site, considerably far from the 500,000 people living in Greater Los Angeles. Today, 18.6 million people live in the LA area, and urban sprawl has brought civilization much closer to Mt. Wilson.

When Kitt Peak National Observatory was first under construction in the late 1950s, it was far from metro Tucson, Arizona, with its population of 230,000. Today, that area houses 1 million people, and Kitt Peak faces much more light pollution.

Even telescopes in darker, more secluded regions – like northern Chile or western Texas – experience light pollution from industrial activities like open-pit mining or oil and gas facilities.

The case of the European Southern Observatory

An interesting modern challenge is facing the European Southern Observatory, which operates four of the world’s largest optical telescopes. Their site in northern Chile is very remote, and it is nominally covered by strict national regulations protecting the dark sky.

AES Chile, an energy provider with strong U.S. investor backing, announced a plan in December 2024 for the development of a large industrial plant and transport hub close to the observatory. The plant would produce liquid hydrogen and ammonia for green energy.

Even though formally compliant with the national lighting norm, the fully built operation could scatter enough artificial light into the night sky to turn the current observatory’s pristine darkness into a state similar to some of the legacy observatories now near large urban areas.

This light pollution could mean the facility won’t have the same ability to detect and measure the faintest galaxies and stars.

Light pollution doesn’t only affect observatories. Today, around 80% of the world’s population cannot see the Milky Way at night. Some Asian cities are so bright that the eyes of people walking outdoors cannot become visually dark-adapted.

In 2009, the International Astronomical Union declared that there is a universal right to starlight. The dark night sky belongs to all people – its awe-inspiring beauty is something that you don’t have to be an astronomer to appreciate.

The Southern Ocean exists in a state of precarious balance. The sea is layered, with cold surface water sitting atop relatively warm water. It’s an inherently unstable situation—all else being equal, the warm water should rise to the top. But it’s saltier and therefore denser, so it lurks below. The cold upper layer, meanwhile, is freshened by snowfall and sea ice, which forms near the coast, then drifts northward into the open ocean before melting.

For the past 10 years, sea ice cover has been in decline as ocean temperatures have warmed. The rapid melting has delivered even more freshwater to the surface, which should strengthen the cold-water-layer’s insulative ability, allowing the sea ice to eventually expand again.

But that feedback loop appears to have been disrupted. New satellite data have revealed that the ocean around Antarctica, against all expectations, is getting saltier.

The study was published in Proceedings of the National Academy of Sciences of the United States of America.

Measuring Where It’s Hard to Measure

Sea ice, rough seas, and 24-hour darkness make it nearly impossible to monitor Southern Ocean salinity from a ship in the winter. Only in recent years has it been possible to measure salinity in the Southern Ocean from space. Satellites can observe the ocean surface’s brightness temperature—a measure of radiation given off at the sea surface. The fresher the water, the higher the brightness temperature.

The technique works well in warmer waters, but in cold waters, brightness temperature doesn’t shift as much as salinity changes. Because these changes are generally quite subtle to begin with, satellites haven’t been able to accurately detect them in polar regions. In these areas, sea ice has also clouded the signal.

Recent advances in satellite technology, however, have greatly improved the sensitivity of brightness readings, and new algorithms allow researchers to clean up noise from sea ice.

Oceanographer Alessandro Silvano of the University of Southampton and his colleagues analyzed the past 12 years of salinity records from the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite. Team member Alex Haumann, a climate scientist with Ludwig-Maximilians-Universität München, in Germany, said having these broad data, which cover the entire Southern Ocean at 25-square-kilometer resolution, is a game changer. “Due to the big coverage and the time series you can get, it’s super valuable. It’s really a new tool to monitor this system.”

“With warming, we expect more freshwater to be flowing into the ocean. So having this saltier water appearing at the surface is quite shocking.”

When the team saw that salinity had increased over that period, however, they couldn’t help but question the technology. To ground truth what they were seeing, they turned to Argo floats—automated buoys that sample water up to 2,000 meters deep. A network of the floats dots the world’s seas, including the Southern Ocean.

To Silvano’s surprise and shock, the floats corroborated the satellite data. “They show the same signal,” he said. “We thought, okay, this is a real thing. It’s not an error.”

Matching the salinity data to trends in sea ice, the team noticed a disturbing pattern. “There is a very high correlation between the surface salinity and the sea ice cover,” Haumann said. “Whenever there’s high salinity, you have low sea ice. Whenever it is low salinity, there is more sea ice.”

“With warming, we expect more freshwater to be flowing into the ocean. So having this saltier water appearing at the surface is quite shocking,” said Inga Smith, a sea ice physicist at the University of Otago in New Zealand who was not involved in the research.

A Shifting Regime

The most plausible explanation for the boost in salinity, Silvano said, is that the delicate layers of Antarctic water have been upset, and the warmer, saltier water below is now bursting through to the surface, making the surface too warm for sea ice to form.

Though he stressed it’s too early to pinpoint a cause for the upwelling, Silvano postulated that it may be driven by stronger westerly winds around Antarctica—a result of the warming climate. He said he fears that Antarctica’s natural damage control mechanism, in which ice melt releases freshwater, which in turn traps the warm deep water and eventually allows more sea ice to form, is now irreversibly broken.

The weakening of the ocean’s stratification instead threatens to set up a dangerous new feedback, whereby powerful convection currents bring up even more warm, salty water from depth, leading to runaway ice loss.

“We have to find ways to monitor the system, because it’s changing very rapidly.”

“We think this could be a regime shift—a shift in the ocean and ice system, where you have permanently less ice,” Silvano said.

Wolfgang Rack, a glaciologist with the University of Canterbury in New Zealand who was not involved in the research, said the satellite record is not long enough to show whether the rise in salinity is an anomaly, or a new state of normal, but “it is quite unlikely that it is a simple anomaly, because the signal is so significant.”

Zhaomin Wang, an oceanographer with Hohai University in Nanjing, China, who was not involved in the research, said the study was a “very firm result,” but cautioned that it’s still too early to conclusively pin the sea ice retreat on upwelling. “It’s quite difficult to disentangle the cause and effect between Antarctic sea ice change and the surface salinity change,” he said, “because it’s a coupled system, making it difficult to determine which process initiates the changes.”

For Haumann, the findings show how crucial new technology is for tracking changes in the Southern Ocean. “We have to find ways to monitor the system, because it’s changing very rapidly,” he said. “This is one of the most distant regions on Earth, but one of the most critical for society. Most of the excess heat we have in the climate system goes into this region, and this has helped us keep the planet at a relatively moderate warming rate.”

“Now we don’t really know what will happen to that,” he said.

—Bill Morris, Science Writer

Citation: Morris, B. (2025), Southern Ocean salinity may be triggering sea ice loss, Eos, 106, https://doi.org/10.1029/2025EO250276. Published on 29 July 2025.

Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Related

Scientists have discovered a new sugar molecule from deep-sea bacteria that could lead to new cancer therapies. The molecule, called EPS3.9, is an exopolysaccharide – a long-chain sugar – produced by the bacterium Spongiibacter nanhainus CSC3.9. According to the study, published in The FASEB Journal, EPS3.9 promotes pyroptosis – an inflammatory form of programmed cell death – effectively killing tumour cells and suppressing tumour growth.

What is pyroptosis and why does it matter?

Pyroptosis is a type of cell death distinct from apoptosis- characterised by inflammation and the release of signalling molecules that activate the immune system. This inflammatory response can be beneficial in cancer therapy, as it not only eliminates cancer cells but also recruits the body’s defences to attack tumours.

EPS3.9’s ability to induce pyroptosis presents a promising strategy for treating cancers that are resistant to conventional treatments, as it combines direct tumour killing with immune system activation.

The science behind EPS3.9’s action

Researchers isolated EPS3.9 from the deep ocean and analysed its chemical makeup, identifying mannose and glucose as its primary sugar components. Laboratory experiments demonstrated that EPS3.9 directly targets five specific membrane phospholipids on human leukaemia cells. This interaction triggers pyroptotic cell death- causing the cancer cells to swell and rupture, releasing inflammatory molecules.

Beyond cell cultures, EPS3.9 was tested in mice with liver tumours. The treated animals exhibited significant tumour shrinkage compared to untreated controls. The compound also appeared  to stimulate the immune system, suggesting a dual mechanism of tumour suppression.

Implications for future cancer therapies

“Our work not only provides a theoretical basis for developing more carbohydrate-based drugs but also highlights the importance of exploring marine microbial resources,” said Dr Chaomin Sun of the Chinese Academy of Sciences, corresponding author of the study.

The marine environment remains an underexplored reservoir of potentially powerful bioactive compounds. This study highlights how marine microbes can provide new molecules with unique mechanisms of action- such as EPS3.9’s ability to trigger pyroptosis.

Carbohydrate-based drugs are particularly appealing because sugars often exhibit low toxicity and high biocompatibility, making them promising candidates for drug development.

Challenges and next steps

While the findings are promising, EPS3.9 is still in the early stages of research. Scientists will need to investigate its safety profile, effectiveness across different cancer types and optimal delivery methods. Clinical trials will ultimately be required to determine whether EPS3.9 or related compounds can be developed into safe and effective cancer treatments for humans.

By harnessing nature’s biochemical diversity, researchers may be able to develop more effective, targeted treatments that both kill tumours and engage the immune system – potentially improving outcomes for cancer patients.

Christina Larson
AP Science Writer

WASHINGTON — It’s almost time for summer’s meteor shower duet.

The Southern Delta Aquariid and the Alpha Capricornid meteor showers peak at the same time — in the early morning of July 30.

Without too much interference from moonlight — the waxing moon will be only about a quarter full — the meteors should appear bright and clear in regions away from city lights.

With each shower expected to produce up to a dozen visible meteors per hour under dark skies, the doubleheader means the total number of meteors “do add up,” said Thaddeus LaCoursiere, planetarium program coordinator at the Bell Museum in St. Paul, Minnesota.

“Look for flashes of light in the night sky,” he said, adding that both are “very nice classic meteor showers.”

The Alpha Capricornids — produced by slower-moving meteors — may have tails that linger slightly longer in the sky, said Nick Moskovitz of the Lowell Observatory in Flagstaff, Arizona.

Viewing of each shower lasts through August 12.

What is a meteor shower?

As the Earth orbits the sun, several times a year it passes through debris left by passing comets and sometimes asteroids.

The source of the Delta Aquariids is debris from comet 96P/Machholz. The Alpha Capricornids stem from the comet 169P/NEAT.

When these fast-moving space rocks enter Earth’s atmosphere, the debris encounters new resistance from the air and becomes very hot, eventually burning up.

Sometimes the surrounding air glows briefly, leaving behind a fiery tail — the end of a “shooting star.”

You don’t need special equipment to see the various meteor showers that flash across annually, just a spot away from city lights.

How to view a meteor shower

The best time to watch a meteor shower is in the early predawn hours when the moon is low in the sky.

Competing sources of light — such as a bright moon or artificial glow — are the main obstacles to a clear view of meteors. Cloudless nights when the moon wanes smallest are optimal viewing opportunities.

And keep looking up, not down. Your eyes will be better adapted to spot shooting stars if you aren’t checking your phone.

When is the next meteor shower?

The next major meteor shower, the Perseids, peaks in mid-August.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

Related

In a stunning display, astronauts aboard the International Space Station (ISS) recently captured a lightning storm illuminating the skies above Singapore. The image, taken during the station’s orbit over Southeast Asia, shows intense bursts of light flickering through cloud cover in the region.

What is it?

The ISS sits in low Earth orbit, providing a unique vantage point for observing large-scale weather phenomena, events such as wildfires, volcanoes, snowfall and more.

In Egypt’s vast deserts, a new
generation of researchers are moving from one fossil-rich site to another to reshape
vertebrate paleontology in the region. Having long been dominated by foreign
expeditions, local researchers are now making their mark across the Arab
region. However, they face persistent challenges, from developing skills, to
conducting fieldwork, and networking with the global community. So, what does
it take to become a successful paleontologist?

Nature Middle East spoke to the team behind Sallam Lab, Egypt’s first vertebrate
paleontology research group, founded by Hesham Sallam, a vertebrate
paleontologist at Mansoura University and the American University in Cairo
(AUC).

Alone with sand and bones

Vertebrate paleontology opens a window on to Earth’s natural history and provides an
essential framework for tracing the origins of life.

As well unearthing fossils, the
discipline involves analysing ancient environments, understanding the evolution
of organisms, and exploring the reasons behind their emergence and extinction.

It takes more than a university
degree to become a vertebrate paleontologist, Sallam says. A scientific
background, along with curiosity and critical thinking, is what shapes a
researcher equipped to carry on.

To Sallam, a good researcher upholds
scientific thinking, while maintaining a solid grasp of the fundamentals of
biology, comparative anatomy, and geology. “This forms the essential framework
for interpreting fossils and placing them in their evolutionary and
environmental context,” he adds.

Tough but Fun

Much of a vertebrate
paleontologist’s time is for desert fieldwork, where discoveries are the
outcome of careful preparation and planning. A discovery is made as a result of
meticulous, robust research. “We know where to look, and which rocks are likely
to contain valuable fossils,” says Sallam.

“Going to the desert is not a
picnic,” says Shorouk Al-Ashkar, a researcher at Sallam Lab. “It is a demanding
mission; advance planning is the cornerstone of fieldwork. This involves
meticulous preparations that include tents and tools that help us withstand the
desert’s blazing heat, in addition to research equipment such as brushes,
plaster, and documentation instruments.”

Al-Ashkar underscores the importance
of building a solid knowledge about the site to be excavated. A researcher
needs to be “well-informed about the site’s history, topography and geological
formation, besides preparing the maps and updated satellite imagery.”

Fieldwork is perhaps the most
exhausting part of the job, requiring a high level of adaptability to harsh
conditions. “But it’s worth it,” says Al-Ashkar. “The moment you uncover a fossil,
all the exhaustion fades away, and the fatigue turns into a surge of energy and
excitement.”

Nuanced process

Al-Ashkar explains, “the desert is
not the place for improvisation,” so the team members work together to preserve
specimens once uncovered. “No fossil is removed until it has been carefully
fixed using a special type of adhesive material suited to its structure,”
Al-Ashkar says. “And every specimen is documented using an identification label
including the exact location, the date of excavation, and an initial
description. A fossil without data holds no scientific value.”

After that, the specimen is jacketed
with a layer of plaster; a universally recognized method for ensuring fossil
safety during transport, especially across rough terrain. The jacketing process
is precise, including horizontal and then vertical carving around the specimen,
followed by securing it with layers of burlap before flipping and transporting
it.

The team document every step with
precision: from the instant a fossil is spotted, through extraction and
jacketing, all the way to its arrival in the laboratory.

Data is documented through
photographs, videos, and written observations, and is then archived both
digitally and physically, offering a reliable point of reference for revisiting
findings or planning future expeditions. The system keeps records of events in
chronological order and ensures transparency and robustness of the resulting
publications.

Paleontologist’s toolkit

 Success in vertebrate paleontology relies on
solid theory and field expertise, and fluency with cutting-edge digital tools.
“It is a field that requires constant learning,” Al-Ashkar says. “We use
advanced software, keep up with the latest research, and treat every day as an
opportunity to gain a new skill.”

Digital fluency now underpins
research quality, Al-Ashkar says. After scanning specimens with high-tech
radiology equipment, the team uses 3D visualization and analysis
software such as Amira and Avizo to convert slides into accurate models of
a fossil’s anatomy. And to examine evolutionary relationships and reconstruct
the fossil’s phylogenetic tree, a tool such as Mesquite is used to record
traits and compare them across species. Tools like TNT and MrBayes are then
used to create potential models for relationships between extinct organisms.

The team also relies on R, a
software for statistical analysis and generating charts that illustrate how
anatomical features are correlated to such variables as body size or ecosystem.
And when it’s time to create visuals, design tools like Photoshop and
Illustrator are indispensable.

Al-Ashkar urges young researchers to
master such tools early on, as they can elevate research quality, and boost the
paper’s chances of publication in prestigious, specialized journals.

Both Sallam and Al-Ashkar encourage
early-career researchers to read constantly and keep abreast of the latest
research. Al-Ashkar recommends reading Vertebrate Palaeontology, by Michael
Benton, which she calls an indispensable reference. She also advises keeping an
eye on the papers published in the Journal of Vertebrate Paleontology.

Facing reality

Passion may ignite a career, but
perseverance keeps it alive. Al-Ashkar recalls entering a male-dominated field
as a young researcher: “It wasn’t easy,” she says. “Yet, as colleagues saw the
results of my work, recognition followed.” Sallam points to an equally pressing
challenge: “We graduate world-class talent, but real jobs in this specialty are
scarce. Without sustained institutional backing, the discipline cannot thrive.”

Besides the social challenges, funding
remains a significant issue, especially when it comes to organizing
resource-intensive expeditions. That said, Sallam remains hopeful:
“Universities and funders are well aware of the value of paleontology in Egypt,
and international partnerships are on the rise.”

Where to start

If you aspire to unearth the next
great dinosaur discovery, start now. Build a solid foundation in biology,
anatomy, and geology. Master specialized scientific software and engage in
fieldwork whenever the opportunity arises. Seek mentors who believe in your potential
and be prepared to work hard long before the rewards appear. As Sallam puts it:
“Find what fires your curiosity, sharpen your skills and never stop learning.
We’re counting on you to carry the torch forward.”

 

_{This
article is translation from the Arabic version published on 9 July 2025}