Reading daily ocean temperatures from red algae

Researchers have developed a method to reconstruct past seawater temperatures from rhodoliths

Max Planck Institute for Chemistry

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Lena Li, first author of the study, holds a rhodolith sample collected in the Red Sea. These free-living algae nodules serve as natural archives, enabling the reconstruction of daily seawater temperatures.

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Credit: Lucio Bravo

Understanding how marine ecosystems respond to a warming ocean requires detailed records of past temperatures.

An international research team led by Johannes Gutenberg University Mainz (JGU) and the Max Planck Institute for Chemistry (MPIC) in Mainz has now found a new way to reconstruct daily seawater temperatures over a four-month period. The key lies in rhodoliths: nodule-like calcareous structures formed by red algae that occur in oceans worldwide. The new approach turns a single nodule into a high-resolution climate archive that can track daily temperature swings as well as warming trends.

Combining three-dimensional X-ray imaging with geochemical analyses and a special algorithm, the team reconstructed daily seawater temperatures from a single rhodolith collected in the central Red Sea.

Their findings are published in the journal Communications Earth & Environment.

An archive that was difficult to read

Typically, researchers reconstruct past climate conditions, for example on reefs, using skeletons of corals, bivalves, and microfossils, such as foraminifera. However, these archives are increasingly constrained by shrinking habitats. Rhodoliths, by contrast, occur all over the world from shallow water down to about 200 meters, making them a widely available archive.

The challenge has been their complex three-dimensional branching structure and asynchronous growth, which complicate the reconstruction of a clear, linear timeline within the layered calcareous skeleton.

The team addressed this by combining several techniques. First, the researchers stained the algae with a dye that specifically accumulates in calcium carbonate and left them to grow in the field for four months, using the stain as a time marker to measure how fast the branches grow. Then, they scanned the nodule using micro-computed tomography, an X-ray technique also used in medical CT scanners, to map its internal growth layers in three dimensions. Next, they fired a laser along each branch to vaporize tiny bits of the algae’s skeleton. A mass spectrometer then analyzed these bits to measure changes in the ratios of the chemical elements magnesium to strontium in each layer, allowing the researchers to determine the seawater temperature at the time each layer had formed. Finally, the team applied a data-alignment algorithm known as dynamic time warping to merge the data from multiple branches into a single, continuous timeline.

“Each branch captures only part of the record, and determining when each branch grew can be difficult” explains Lena Li, lead author and researcher at JGU and MPIC. “By mathematically aligning the growth of the branches, we can reconstruct a continuous, daily timeline from a single nodule.”

Validation in the Red Sea

The researchers applied their method in the Red Sea, an extremely salty, nutrient-poor basin with high evaporation and intense sunlight. On its shallow reef flats, water temperatures range from about 18 to nearly 38 °Celsius over the year. These conditions make a precise, high-frequency temperature record particularly valuable.

Using a single rhodolith from a central Red Sea reef flat, the team reconstructed 133 days of temperature data from March to July 2024. They then compared the results with measurements from temperature loggers at the site. The reconstruction closely matched the observed values, capturing both the seasonal warming trend and short-term variations.

Beyond rhodoliths

The study is a proof of concept that could be extended to rhodoliths across the globe. “In principle, the alignment technique could also be applied to other fragmentary records, such as several coral cores from a single reef or temporally overlapping records from different organisms, to combine them into a single continuous record spanning longer intervals,“ Li concludes.

In the future, this approach could also be applied to rhodoliths from other locations. This would enable the collection of high-resolution climate data across larger regions and longer time periods. Ultimately, this would help to better reconstruct paleoclimatic development and more accurately predict the impacts of global warming on threatened marine ecosystems.

Participating institutions

The study was carried out by an international team from six institutions: Johannes Gutenberg University Mainz (Institute of Geosciences) and the Max Planck Institute for Chemistry in Mainz, together with Kiel University / GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany), the University of Barcelona (Spain), the University of Toronto (Canada) and King Abdullah University of Science and Technology (KAUST, Saudi Arabia), where the rhodoliths were collected and imaged

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Journal

Communications Earth & Environment

DOI

10.1038/s43247-026-03603-y 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Rhodoliths can act as daily resolution paleotemperature archives in the Red Sea.

 

Busseiron: Understanding the origin and evolution of a distinct branch of physics in Japan

Researchers explore the history of Bussieron’s path from a loosely defined label for matter-related research to an established discipline

Institute of Science Tokyo

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This work sheds light on how a unique term for matter-related research in Japan emerged and evolved during the 20th century.

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Credit: Institute of Science Tokyo

A new etymological study shows that the terms for scientific disciplines can take shape through naming and classification as much as through theories and institutional usage, as reported by a researcher from Japan. Focusing on Busseiron, a Japanese term for the study of matter, the study traced its use across textbooks, journals, and scientific meetings. Analysis revealed how the term gradually brought together diverse matter-related research and became a durable branch of physics in Japan.

The study of matter, namely its structure, properties, and behavior, has long been one of the central pillars of modern physics. In Japan, this area of research came to be known by the distinctive term Busseiron during the 20th century, which roughly translates to “theory of the properties of matter.” Over the course of a few decades, Busseiron—also referred to in later usage as Bussei Butsurigaku, or simply Bussei—grew into a full-fledged academic discipline, one that would eventually overlap substantially with what is now called condensed matter physics.

Interestingly, the term Busseiron has often been treated as a uniquely Japanese label, with a somewhat unclear scope. Its meaning shifted over time and did not map neatly onto Western categories such as “solid-state physics” or “physical chemistry.” When analyzing the terms used for disciplines, historians of science have typically focused on the development of theories, research communities, and institutions, leaving the role of language largely unexamined. This makes Busseiron a particularly useful case for asking a more basic question: how does the field take shape and endure through the words scientists settle on to describe it?

A new study by Researcher Hiroto Kono of the National Museum of Nature and Science, with support from Professor Masashi Shirabe of the School of Environment and Society, Institute of Science Tokyo (Science Tokyo), Japan, takes up this question. Published in the journal Isis, this work examines how Busseiron evolved into the name of an academic discipline that stood the test of time. By tracing how the term was used, debated, and institutionalized, Kono reconstructed the historical process through which a major branch of Japanese physics developed. The study was made available online on April 07, 2026, and published in Volume 117, Number 2 of the journal on June 01, 2026.

First, Kono examined textbooks, journal articles, conference programs, and roundtable discussions from the 20th century. He tracked how Busseiron’s scope expanded over time, comparing this with the parallel development of solid-state and condensed matter physics in the West. This analysis showed that Busseiron did not simply grow out of the specific wartime research that first used the name. Instead, its meaning kept broadening, absorbing new topics ranging from ferroelectricity to electron emission to polymer chemistry, eventually including subjects that had originally been excluded from it.

One factor that held this loosely defined field together was a clear dichotomy against Soryûshiron, the Japanese term for the theory of elementary particle physics. Anything related to matter yet distinct from particle physics could be placed under the Busseiron label, which had become an umbrella term by the end of the 1940s. Notably, an attempt by some of the field’s own founders to replace the word with “chemical physics” failed, and the looser term persisted instead. “This study offers a new perspective by showing that the formation of academic disciplines can be understood not only through the development of theories and research communities, but also through the history of names and language,” Kono explains.

One of the main takeaways from this work is that even as research becomes increasingly international, the terminology scientists use can remain deeply shaped by local language and history. “As this Japanese case attests, etymological studies offer new possibilities for exploring the role of national contexts in the development of disciplines in an age when the globalization of science tends to be taken for granted,” concludes Kono.

 

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About Institute of Science Tokyo (Science Tokyo)
Institute of Science Tokyo (Science Tokyo) was established on October 1, 2024, following the merger between Tokyo Medical and Dental University (TMDU) and Tokyo Institute of Technology (Tokyo Tech), with the mission of “Advancing science and human wellbeing to create value for and with society.”

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Journal

Isis

DOI

10.1086/740958 

Method of Research

Content analysis

Subject of Research

Not applicable

Article Title

Coining a Discipline: The Formation and Perpetuation of a Japanese Branch of Physics of Matter

 

When tree shade points the way

Analysis tool shows where shade already exists and where trees should be planted for cooler, more walkable streets.

Heidelberg Institute for Geoinformation Technology

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Screenshot of the tree shade indicator in the Climate Action Navigator, visualizing the tree shade distribution in Innsbruck.

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Credit: Climate Action Navigator

Heidelberg, 11.08.2026. In some city districts, more than a third of pedestrian streets sit under tree cover. In others, the figure is barely ten percent. To make such gaps visible and give cities a more differentiated view, HeiGIT (Heidelberg Institute for Geoinformation Technology) has added a new indicator to its existing Climate Action Navigator. Local governments and civil society organizations receive a free, street-level overview of where shade is present and where it is missing, so they can take targeted action such as planting trees or directing tourists toward shaded routes to attractions.

Tree shade has a substantial effect on the temperature of individual streets. Citywide averages are often coarse and can hide where residents are most exposed to heat on their daily routes. In Innsbruck, for example, tree cover reaches about 30 percent overall. Most of the shaded paths, however, lie outside the city center, while heavily used streets in the city itself are often left in full sun.

Shaded routes make the daily commute to school or work more pleasant, and they also indicate which neighborhoods remain livable as summer temperatures rise and which do not. Claudia Schmiedeberg of the GLEN Study adds: “Understanding how climate change affects society as a whole requires a close look at how local surroundings shape daily behavior and well-being over time. Linking the tree shade indicator with longitudinal survey data shows how urban environments influence decisions and how unevenly these effects are distributed across neighborhoods.”

Knowing where to act

The tool was developed at the request of urban planners and non-governmental organizations working on pedestrian-friendly city design. It gives municipalities a basis for deciding where new trees are needed and where existing tree cover already contributes to livable streets. Jim Walker from Walk21 Foundation notes: “This indicator gives us comparable numbers, street by street, so city administrations have the evidence to prioritize infrastructure investment where it will keep people moving through the hottest months”. Linking the tree shade data with school catchment areas, for instance, reveals which routes offer children more sun protection on their way to school than others.

How the indicator is calculated

The indicator analyzes where pedestrian walkways directly overlap with tree canopies standing two meters or taller, a height that separates real shade from low shrubs and ground cover. Simulating a high noon scenario when solar exposure is strongest, the tool measures shade at its weakest point of the day, giving planners a worst case benchmark for targeted interventions.

The same data and method apply everywhere, so a small town and a global capital can be measured on equal footing. Two contrasting examples illustrate this: In the historic city of Maribor, roughly 35% of the pedestrian network is covered by trees. Meanwhile, in the university hub of Tempe, Arizona, this figure is just above 7%. Cities can use this free and open tool to see where they stand and where to act next.

“We wanted to bypass the barrier of local data scarcity. With high-resolution global canopy datasets, we can offer any municipality a granular diagnostic tool for free. This democratizes access to information, allowing planners to target greening initiatives where they are needed the most,” says Dr. Kirsten von Elverfeldt, Community engagement manager at HeiGIT.

Everyone can access the dataset and see how their own municipality performs by visiting the Climate Action Navigator platform: https://climate-action.heigit.org/dashboard/

Video: Tree shade indicator 

Contact person for Climate Action Navigator: Kirsten von Elverfeldt kirsten.vonelverfeldt[at]heigit.org

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Method of Research

News article

 

Scientists discover why people who crave sweets make more impulsive choices

National Research University Higher School of Economics

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Having a sweet tooth may be linked not only to eating habits but also to the way people make decisions. Researchers at HSE University have found that people with a preference for sweet foods tend to behave more impulsively—not because they want immediate rewards, but because they are less willing to tolerate uncertainty. These findings may help improve treatments for addiction. The study findings have been published in Frontiers in Psychology.

Impulsive choice—preference for a smaller immediate reward over a larger delayed one—is considered an important behavioural marker of self-control. However, the mechanisms underlying this tendency are still not fully understood. Previous research has shown that people with greater sensitivity to rewards are more likely to make impulsive choices, but the reasons behind this relationship have remained unclear.

Researchers at the HSE Institute for Cognitive Neuroscience experimentally investigated the relationship between impulsivity and reward sensitivity using preference for sweet tastes as an indicator.

In experiments involving 149 young participants, the researchers used the standardised Kampov-Polevoy sweet-taste preference test to classify participants as either sweet likers—those who preferred the most concentrated sucrose solution—or sweet dislikers. The participants then completed a series of tasks assessing risk aversion and impulsivity, in which they chose between smaller and larger rewards, as well as between immediate and delayed rewards.

Sweet likers were significantly more likely to choose a smaller but guaranteed reward, demonstrating greater risk aversion. In the impulsivity task, they also tended to prefer a smaller immediate reward over a larger delayed one. However, when both options involved a delay, they were more willing to wait for the larger reward. After the researchers accounted for each participant's level of risk aversion, the apparent impulsivity of the sweet likers largely disappeared.

The researchers suggest that sweet likers choose immediate rewards not because they are unwilling to wait, but because delayed rewards always involve uncertainty, which they tend to avoid.

According to the authors, this effect may be linked to the brain’s opioid system. Sweet taste preference is associated with the activity of receptors that are involved not only in experiencing pleasure but also in assessing threats and uncertainty. If individuals with a strong preference for sweet tastes have heightened sensitivity in this system, they may not only derive greater pleasure from rewards but also perceive potential losses or uncertainty more intensely.

'We are used to thinking of impulsivity as an inability to delay gratification. However, our findings point to a different mechanism: choosing a smaller immediate reward may stem from a desire to avoid uncertainty rather than from a desire to receive a reward as quickly as possible. This changes our understanding of the nature of impulsive behaviour,' says the study’s lead author, Anna Davidovich, Research Assistant at the Centre for Cognition & Decision Making of the HSE Institute for Cognitive Neuroscience.

The findings open up new perspectives for understanding the biological basis of impulsivity and risk-taking behaviour. In the future, the researchers plan to investigate the neurobiological mechanisms underlying these effects using EEG and computational models of decision-making. They believe that this research could contribute to improving the diagnosis and treatment of various addictions.

The study was conducted with support from HSE University's Basic Research Programme.

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Journal

Frontiers in Psychology

DOI

10.3389/fpsyg.2026.1764306 

Article Title

Sweet-taste liking is associated with preference for less risky and immediate rewards in economic decision-making

 

Nicotine use linked to mental health problems in adolescents

University of Gothenburg

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Adolescents who use nicotine are more likely to report symptoms of anxiety, depression, and other mental health problems than their peers who do not use nicotine. Girls appear to be particularly vulnerable, according to three recent studies from the University of Gothenburg. 

In one study of nearly 3,000 Swedish high school students, almost 80 percent of the girls who used nicotine reported clinically relevant symptoms of anxiety. The associations were found for both traditional tobacco products and tobacco-free nicotine products such as nicotine pouches and e-cigarettes. 

The researchers also followed approximately 1,500 adolescents in southern Sweden over time, from lower secondary school through high school. Depressive symptoms and suicidal ideation were more common among adolescents who smoked. Girls who increased their tobacco use over time were also more likely to experience worsening sleep problems, anxiety, low mood, and difficulties concentrating. The researchers say the marked differences between girls and boys warrant further investigation. 

Girls may be particularly vulnerable 

Johanna Andersson, physician and PhD student at the Sahlgrenska Academy, University of Gothenburg, is one of the lead authors: 

“We see clear differences between girls and boys, with girls who smoke appearing to be particularly vulnerable. At the same time, we need a better understanding of how nicotine pouches affect mental health, especially among adolescent girls, where the use of nicotine pouches has increased so rapidly,” she says. 

The findings come from questionnaire-based studies and long-term follow-up of adolescents, combined with experiments in rats examining how nicotine affects neuronal signaling. In the animal study, published in the journal Neuropharmacology, the researchers found that nicotine affected the amygdala, a brain region that plays a key role in emotional regulation and stress responses. The effects were most pronounced in female rats. 

Nicotine alters neuronal communication 

Nicotine altered communication between neurons and produced long-lasting changes in brain activity that persisted even after the nicotine had left the body. 

Louise Adermark, Professor at the Sahlgrenska Academy, University of Gothenburg, is one of the principal investigators behind the studies. 

“One of the key findings is that we see similar patterns across several different studies using different types of data. However, we still cannot determine cause and effect. The animal studies demonstrate biological changes in the brain that could contribute to increased vulnerability to anxiety and stress-related symptoms,” says Louise Adermark. 

The researchers emphasize that socioeconomic factors, stress, alcohol use, other substance use, and individual vulnerability also influence the risk of both mental health problems and nicotine use. At the same time, they say the findings raise questions about how new nicotine products affect the developing brain and whether girls may be particularly sensitive to the effects of nicotine. 

Studies:

Sex-specific associations between tobacco use and youth mental health: prospective and cross-sectional findings from Swedish adolescents (Nicotine & Tobacco Research, June 2026) https://doi.org/10.1093/ntr/ntag148

Gender-Specific Associations Between Tobacco and Tobacco-Free Nicotine Use and Symptoms of Anxiety and Depression in Swedish Adolescents (Tobacco Use Insights, May 2026) https://doi.org/10.1177/1179173X261455075

Nicotine produces a sex- and subregion-specific hypoglutamatergic state in rodent amygdala which can be reversed by motor-skill training (Neuropharmacology, February 2026) https://doi.org/10.1016/j.neuropharm.2026.110879

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Journal

Nicotine & Tobacco Research

DOI

10.1093/ntr/ntag148 

Method of Research

Observational study

Subject of Research

People

Article Title

Sex-specific associations between tobacco use and youth mental health: prospective and cross-sectional findings from Swedish adolescents

X-rays: beyond the Nobel Prize limit

An experiment jointly performed by teams at University of California San Diego and TU Wien has discovered a new quantum regime of coherent X-ray generation with higher energies than they should be able to reach according to the conventional rules

Vienna University of Technology

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When certain atoms are irradiated with laser light, they can themselves produce a very different kind of laser light: laser pulses with extremely high frequencies in the X-ray range. These laser pulses, with which record-breaking results were achieved at TU Wien in the 1990s, were the subject of the 2023 Nobel Prize in Physics. However, the theoretical model of this effect makes a clear prediction: there is an upper limit to the energy, depending on the properties of the laser beam directed at the atoms. Above a certain value, known as the energy cutoff, hardly any X-rays are produced.

Now, however, a new experiment jointly performed by teams at TU Wien and University of California San Diego has succeeded in overcoming this textbook cutoff rule: using helium atoms, the researchers reached a much higher energy range than the standard theory would allow. The reason for this lies in the interaction between the two electrons in the helium atom: they can release their energy simultaneously. The effect has now been published in the journal Nature Photonics.

Tearing an electron away from an atom

“The mechanism behind short X-ray pulses has been well known for a long time,” says Prof. Tenio Popmintchev from the Institute of Photonics at TU Wien. “The laser tears a single electron away from the atom. The electron is then accelerated in the laser’s electric field until it eventually collides with the atom again. The energy it loses in the process is emitted in the form of light.” This produces laser pulses with frequencies much higher than that of the laser originally directed at the atom.

Nobel laureate Ferenc Krausz used precisely this effect in the 1990s. Today, Tenio Popmintchev and his team conduct research at the same institute where Ferenc Krausz worked at the time—and they are now going significantly beyond what was possible then. “It can be shown that when the electron returns to its atom, it generates a whole range of different frequencies with roughly equal intensity,” says Dimitar Popmintchev, postdoc in Tenio Popmitchev’s team at TU Wien. “But there is an upper limit. Frequencies above this limit are much weaker; it is simply not possible to exceed a certain maximum frequency.”

Two electrons are better than one

But what happens when not just one electron is involved, but two? Tenio Popmintchev’s team used intense UV lasers and helium atoms, from which two electrons can be removed, one after the other. The first electron is released and accelerated, followed by the second. The two electrons are not independent of one another, however: they are quantum-mechanically correlated.

“Using UV driving pulses, we can arrange for both electrons to return to the atom at exactly the same time,” says Dimitar Popmintchev. “The energy of two electrons is then released all at once. And when more energy is available, a single higher-energy X-ray photon with higher frequency can also be generated.”

The team discovered these remarkably high X-ray frequencies experimentally. In the measured coherent spectrum, a second, weaker plateau appeared well above the previously known range, at substantially higher photon energies.

This was observed only in helium atoms – an atom with extremely strong electron correlations. The valance electrons of argon and neon atoms do not display this behaviour—further evidence that the special interplay between the two electrons in the helium atom is crucial.

This new “kind” of coherent X-ray radiation is particularly interesting as a new spectroscopic “sensor” of electron-electron correlations. Its shape, its energy limit and its dependence on the polarization of the laser can provide information about how two electrons interact on attosecond timescales. In the long term, the principle could also be transferred to molecules or strongly correlated solids. High-harmonic generation, which once paved the way for attosecond physics, is thus itself becoming a probe of quantum many-body processes, fundamentally important for quantum computing and design of function of advanced nanomaterials.

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Journal

Nature Photonics

DOI

10.1038/s41566-026-01976-2 

Article Title

Correlated electrons extend X-ray high-harmonic generation beyond the single-electron limit

Article Publication Date

7-Aug-2026