It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Thursday, February 22, 2024
Putin's cod war: Russia tears up treaty that allowed UK trawlers to catch fish in Russian sea
Vladimir Putin has started a war on fish and chip shops in the UK after ripping up a treaty that allowed UK fishermen to trawl the sea for Russian cod.
Putin 'personally' made the decision to disregard the 70-year-old treaty in response to the UK imposing sanctions on Russia in the wake of its invasion of Ukraine.
The end of the treaty was confirmed by the Russian Parliament, almost seven decades it was signed by the Soviet Union.
It allowed British vessels to fish in the Barents Sea in eastern Europe, but those who do now could face the wrath of Putin's warships.
The speaker of the Russian parliament, Vyacheslav Volodin, even went as a far as to say that it was a move that would affect 40 per cent of British people's diet.
Vladimir Putin. Picture: GettyBarents Sea. Picture: Getty
"Putin returned Crimea to Russia, and he will forever go down in history as the president who returned our territory," he said.
"And it's him again, it's his decision exclusively: he gave us back our fish.
"Because it was eaten for 68 years by the unscrupulous British."
Volodin continued: "They announced sanctions against us, but they themselves make 40 per cent of their diet, their fish menu, from our cod.
"Now let them lose weight, get smarter. Because it is cod and other species of fish, including haddock, that form 40 per cent of their diet. And it's one of their favourite dishes."
“Now we have returned this favourite dish to them on the initiative of our President.”
Trawlers will no longer use the Barents Sea. Picture: Getty
But according to Andrew Crook, President of the National Federation of Fish Friers (NFFF), said it is an attempt to make Russia look like it was responding to British sanctions.
"The reality is that we do not fish in Russian waters in the Barents Sea."There is only one British register vessel that could do, the kirkella, but it doesn’t go that far.
"The life cycle of cod is such that the young fish go to that area to grow to it is left alone to grow so there is the biomass required in the future when it returns to the fishing grounds in the Barents Sea."
New research shows how empathy can be socially transmitted
Prof. Dr. Grit Hein's latest assessments of empathic abilities once again challenge the old adage, "You can't teach an old dog new tricks." It seems that not only children but also adults can adopt empathic responses from close caregivers in addition to their genetic predispositions. Adults, too, are malleable and can learn to be more or less compassionate through observing others.
The professor of Translational Social Neuroscience at the Center of Mental Health of the University Hospital Würzburg (UKW) has managed to capture this complex social phenomenon through mathematical models, a procedure known as Computational Modeling, and has plastically mapped it in the adult brain using functional Magnetic Resonance Imaging (fMRI).
Her findings, published in the Proceedings of the National Academy of Sciences, provide a computational and neuronal mechanism for the social transmission of empathy, explaining changes in individual empathic responses within both empathic and non-empathic social environments. Grit Hein has, in a sense, formalized the process by which empathy is transmitted.
Social transmission of empathy was tested in various studies. The central question of Hein's research was whether empathy, or lack thereof, for another person's pain, is socially transmitted. In a total of four studies, participants first watched videos of hands receiving painful stimulation and indicated their own feelings during this experience on a rating scale.
After providing their own rating, they were shown the empathic or non-empathic responses of other individuals to the same videos. Finally, participants rated their empathy again, this time regarding the pain of a new person. With this experimental setup, Grit Hein and her team were able to test how and if a person's empathy changes in the presence of empathic and non-empathic peers
Transmission of empathy relies on observational reinforcement learning
By observing the empathic reactions of others, participants learned to be more or less empathetic. "Empathy ratings increased or decreased depending on whether empathic or non-empathic reactions were observed. Interestingly, the neuronal response to the pain of another person also changed," says Grit Hein.
The neural changes measured in the fMRI scanner were reflected in altered connectivity of the anterior insula, a brain region associated with empathy processing. Hein and her team's research demonstrates that these neural changes can be explained by mathematical learning models. This implies that increased or decreased empathy is genuinely induced through learning from others and is not merely an imitation or displayed for the purpose of pleasing others.
Investing in an empathetic environment is worthwhile in a professional context. Does this mean that those who wish to have a good team must create a conducive environment? "Absolutely," responds Grit Hein. "It is essential to understand that adults can learn or unlearn empathy through observation, even from individuals they do not know."
Consequently, those who create a work environment lacking in empathy for reasons of cost-saving, time constraints, or mismanagement must be aware that such behavior shapes employees in the long term and, in turn, affects their interactions with clients or patients.
Previous studies have shown that positive empathy can transition into prosocial motivation, increasing cooperation and willingness to help. However, excessive empathy can also lead down a different path, inducing stress and potentially resulting in burnout or complete withdrawal. Additionally, empathy can be perceived as demanding.
'Respect is the soil for empathy'
"The good news from our studies is that we have the means to shape empathetic ability in adults through appropriate measures in both directions," says Grit Hein. "It is possible to learn positive empathy from others. However, for empathy to thrive long-term, it requires an atmosphere of mutual respect. One can respect someone without having empathy for that person, but it is challenging to develop empathy if the other person is not respected as a human or if disrespect is accepted in society."
The complex social interactions are among the research focuses of Grit Hein. To understand these interactions, it is necessary to start very basically, establish the fundamental mechanisms, and gradually incorporate social factors like puzzle pieces. For this reason, the current study was conducted exclusively with women.
However, the social empathy transmission effect was replicated in different environments (MRI and laboratory) and with female participants of various ages and ethnicities. Both younger and older European and Asian participants responded similarly.
Subsequent studies on empathy that include mixed genders represent an appealing approach. At the moment, Grit Hein is further examining whether the model can also be applied to other social behaviors, such as selfishness or aggression.
More information: Yuqing Zhou et al, The social transmission of empathy relies on observational reinforcement learning, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2313073121
Orchids are one of the most species-rich families of flowering plants, rivalled only by the daisy family (Asteraceae). Pictured: Lepanthes cassicula. Credit: Oscar Perez, RBG Kew
In a new study published in New Phytologist, scientists at the Royal Botanic Gardens, Kew, along with partners in Latin America, Asia and Australia, present an updated family tree of orchids, tracing their origins to the northern hemisphere some 85 million years ago. Not only does the study shed new light on their complex and fascinating evolutionary history, but the study's authors hope their findings will help inform future orchid conservation planning.
The orchid family, Orchidaceae, is often lauded by scientists as one of the greatest evolutionary marvels within the plant world. Not only are these flowering plants found on every continent except the Antarctic and in virtually every habitat, including north of the Arctic Circle, but they are also incredibly diverse, with an estimated 29,500 species—nearly three times more than the recognized number of bird species globally.
It is generally accepted that orchids originated as far back as around 90 million years or more ago, but they were previously thought to have emerged on the supercontinent Gondwana, in what is present-day Australia. However, the new study indicates their common ancestor may have originated in the northern hemisphere, on the supercontinent Laurasia, before spreading out further into the world.
RBG Kew's scientists came to this conclusion after assembling the most densely sampled orchid tree of life ever produced. This new family tree includes nearly 40 percent of all the accepted orchid genera and about seven percent of the known species diversity.
This tree was reconstructed by merging different types of DNA sequence data obtained from across the orchid family. Central to the task was new, 'high throughput' gene capture data produced at RBG Kew as part of the Plant and Fungal Tree of Life (PaFToL) project. The resolution of the tree was further enhanced by combining the results with already published DNA sequences of many orchid species.
These DNA 'barcoding' sequences reflect decades of effort to establish family relationships between the various branches of the orchid evolutionary tree. Taken together with geographical distribution information, this wealth of data yielded a new orchid tree of life that also shows how orchid species diversity is distributed globally.
Dr. Natalia Przelomska, Lecturer at the University of Portsmouth and Research Associate at RBG Kew says, "Generating the 'gene capture' data in the laboratory from such a range of species wouldn't have been possible without the geographical and historical breadth of the collections accessible for research in RBG Kew's Herbarium."
"I had the privilege of extracting DNA from field samples ranging from those recently collected by multiple field botanists involved in this research, going back to botanists such as A.C. Maingay and E.L. Ekman, who were exploring the Old-World tropics and Neotropics in the 19th and 20th centuries."
Orchids are one of the most species-rich flowering plant families (rivaled only by the daisy family, Asteraceae) but also one of the most threatened. Some of the biggest threats to orchids today include deforestation, illegal trade, and climate change, which can cause extinctions or reductions in their ranges and population sizes.
As reported in RBG Kew's State of the World's Plants and Fungi 2023 report, 45 percent of the world's known plants are estimated to be at risk of extinction, and this figure is even higher within the orchid family, with an estimated 56 percent of species under threat.
Having a better understanding of the individual branches of the orchid family tree and how they all connect will help scientists discover and describe new orchid biodiversity. In particular, they hope to achieve this in those parts of the globe where biodiversity loss is, unfortunately, accelerating.
According to the new report, one way to help conserve orchids is to understand better patterns of speciation—the evolutionary process by which populations develop into distinct species. In this case, it can reveal which ecosystems have above-average levels of orchid diversity as well as the highest evolutionary potential to host new orchid diversity.
Dr. Oscar Pérez, Research Leader—Integrated Monography at RBG Kew, says, "Our study is the first in revealing, at a global scale, which ecological regions have both the highest orchid evolutionary potential and species richness. That is, ecological regions that in very recent timescales (i.e., the last 2-3 million years) have served as the cradle of unprecedented speciation that resulted in the accumulation of remarkably high levels of orchid species diversity."
"We think that such areas could have the carrying capacity to harbor even more diversity in the immediate future, for as long as their native ecological regions are protected. As such, the information our study provides on speciation and species-rich patterns can inform policies about the prioritization of ecosystems for their conservation."
Unfortunately, orchids are going extinct at an alarming rate when compared to the time it took them to speciate—about 5 million years. This indicates they may not be able to bounce back from extinction in human timescales, even without a precise estimate of the number of orchid species that have gone extinct.
Prof. Alexandre Antonelli, Director of Science at RBG Kew and senior author of the study, says, "Orchids are not only extraordinary jewels of nature, they also hold untold mysteries about life on Earth: how species evolve, adapt and move. Safeguarding their future is critical for protecting the complex interactions they play in ecosystems and making sure those stories can one day be unveiled by scientists."
This new study is but the first step in the scientists' goal of drawing up a complete orchid tree of life encompassing all known genera. The authors also aim to establish the orchid family as the model lineage of choice for understanding how speciation and extinction happened across different ecosystems worldwide. Furthermore, this will help to understand how climate change, deforestation and illegal trade can affect the distribution of such species diversity in the near future.
More information: Oscar A. Pérez‐Escobar et al, The origin and speciation of orchids, New Phytologist (2024). DOI: 10.1111/nph.19580
Hiroshima fallout debris linked to first solar system condensates
by Hannah Bird , Phys.org
Diagrammatic explanation of the evolution of the fireball in the 5 seconds after Hiroshima nuclear bomb detonation. Credit: Asset et al, 2024
The atomic bombing of Hiroshima, Japan, by the United States in August 1945 was not only devastating at the time, resulting in the deaths of hundreds of thousands of people, but it has had long-standing impacts to the present day, particularly the elevated incidence of cancer from radiation.
Continued research of Hiroshima Bay has uncovered a new kind of debris from the fallout, known as Hiroshima glasses. These formed from vaporized materials of the bomb and the surrounding landscape and infrastructure being targeted.
New research published in Earth and Planetary Science Letters has analyzed the chemical and isotopic compositions of these glasses to ascertain their formation process during the nuclear event.
Nathan Asset, of Université Paris Cité, France, and colleagues determined that rapid condensation (1.5–5.5 seconds) within the nuclear fireball (temperature 3,200–1,000 Kelvin) was the primary process. This is akin to the process by which the first solids (condensates) in the solar system, calcium-aluminum-rich inclusions (CAIs) of primitive meteorites (chondrites), would have formed from the vaporization of interstellar dust and nebula gas.
To investigate this further, the research team identified four types of glasses within the 94 specimens of fallout debris: melilitic (low silica, high calcium oxide and rich in magnesium oxide), anorthositic (high aluminum oxide contents and iron-bearing), soda–lime (rich in silica and sodium oxide) and silica (~99% silica). The origin of the silica glass could not be separated from sand grains on the beach, but the soda–lime glasses are similar to compositions of industrial origin.
Examples of Hiroshima glasses under optical (C, E, F) and scanning electron microscope (A, B, D). Credit: Asset et al, 2024
Reconstructing the formation of these glasses, the researchers state the plasma fireball exploded 580 m above the city with a radius of 260 m, a peak temperature of 107 K and a pressure of 106 atmospheres. A thermal wave touched the ground at temperatures of 6,287°C.
Within a mere 0.35 seconds, the pressure dropped to match that of the surrounding atmosphere and within 10 seconds the temperature decreased to 1,500–2,000 K and vaporization ceased. In the immediate 0.5–2 seconds after the explosion, city materials (concrete, iron and aluminum alloys, industrial glass and soil) were vaporized and mixed with sand, Ota River water and the atmosphere to produce the various glasses.
There is some difficulty in estimating the actual quantities of each component that was vaporized, as not all buildings were destroyed; for example, some built to withstand earthquakes did survive the blast and therefore some concrete, iron and bricks were not vaporized.
Additionally, different materials require different amounts of energy to vaporize and therefore form condensation nuclei at different stages of the glass-forming process (e.g., river water inclusion would be sustained for longer as it requires less energy than concrete).
The isotopic composition of silica within the Hiroshima glasses was -23.0 ± 1.8 ‰ to -1.5 ± 1.1 ‰, while that of oxygen via mass-independent fractionation was -3.1 ± 0.6 ‰, all of which fall within the realms of the composition of CAIs. The research team used the results of the fractionation to determine melilitic glasses were the first to form, then anorthositic, followed by soda–lime and finally almost pure silica.
While the composition of the environment of Hiroshima glass formation differs from that of CAIs (temperature 3,500 K for Hiroshima and 2,000 K for the solar accretion disk, 1 bar pressure for Hiroshima and 10-3–10-6 bar for solar disk, oxygen-rich environment for Hiroshima and hydrogen-rich for solar disk) and the time over which the events occurred (<20 minutes for Hiroshima versus many years for the solar disk), understanding the processes occurring during the gas-solid transition helps us uncover more about the origins of our solar system and all that has developed since.
More information: Nathan Asset et al, Condensation of fallout glasses in the Hiroshima nuclear fireball resulting in oxygen mass-independent fractionation, Earth and Planetary Science Letters (2023). DOI: 10.1016/j.epsl.2023.118473
A new paper in Nicotine & Tobacco Research, published by Oxford University Press, finds that banning the sale of menthol cigarettes would likely lead to a meaningful reduction in smoking rates.
Menthol cigarettes are of particular public health concern because studies have found that the cooling effects of menthol mask the harshness of cigarettes, making it easier for young people to start smoking. Prior research has also found that menthol in cigarettes makes it easier for smokers to absorb nicotine, which results in greater dependence. Menthol smokers also find it harder to quit smoking compared to those who smoke non-menthol cigarettes.
Prevalence rates of menthol cigarette use among cigarette smokers vary globally. Some 7.4% of smokers in Europe use menthol cigarettes. In the United States, however, some 43.4% of adult smokers used menthol cigarettes in 2020. Menthol cigarettes are disproportionately used by young people, racial/ethnic minorities, and lower-income smokers. About 81% of non-Hispanic Black smokers in the US use menthol cigarettes, as compared to 34% of White smokers. More than 170 US cites and two states, several countries (e.g., Canada, Ethiopia), and the European Union ban the sale of menthol cigarettes.
Researchers here measured the effects of these policies. The investigators conducted a systematic search of studies published in English up to November 2022 (using PubMed/Medline, CINAHL, PsycINFO, Web of Science, and Embase), to discover how menthol bans change smoking behavior. The researchers involved in this study looked at 78 prior studies, mostly from Canada, the European Union, and the United States.
The study finds that the effect of menthol cigarette bans are substantial. The results show that while 50% of menthol smokers switched to smoking non-menthol cigarettes, almost a quarter (24%) of menthol cigarette smokers quit smoking altogether after a menthol ban. Some 12% switched to other flavored tobacco products, and 24% continued smoking menthol cigarettes. The study also finds that national menthol bans appear more effective than local or state menthol bans, as quit rates were higher in places with country-wide bans.
“This review provides compelling evidence for the US Food and Drug Administration’s proposed ban on menthol cigarettes,” said the paper’s lead author, Sarah Mills. “In December 2023 the White House postponed banning menthol cigarettes. Our review of the evidence suggests this delay is causing harm to the health of the public, especially among Black communities. Contrary to industry claims, studies find no increase in the use of illicit products. A menthol cigarette ban would provide the greatest benefits to Black people who smoke. As a result of targeted marketing by the tobacco industry, today every 4 in 5 Black smokers use menthol cigarettes.”
The paper, “The Impact of Menthol Cigarette Bans: A Systematic Review and Meta-analysis,” is available (at midnight on February 21th) at: https://doi.org/10.1093/ntr/ntae011.
To request a copy of the study, please contact: Daniel Luzer daniel.luzer@oup.com
The Impact of Menthol Cigarette Bans: A Systematic Review and Meta-analysis
ARTICLE PUBLICATION DATE
21-Feb-2024
COI STATEMENT
One of the authors of the paper has served as a paid expert consultant representing plaintiffs in litigation against e-cigarette and tobacco companies.
CLOUDS HAVE A NUMBER OF IMPORTANT FUNCTIONS. THEY ACT AS REFLECTORS WHEREBY WATER DROPLETS IN THE CLOUD REFLECT RADIATION BACK TO THE EARTH, WHICH CONTRIBUTES TO THE GREENHOUSE EFFECT.
When clouds meet clear skies, cloud droplets evaporate as they mix with dry air. A new study involving researchers from the University of Gothenburg has succeeded in capturing what happens in a model. Ultimately, this could lead to more accurate climate modeling in the future.
The clouds in the sky have a significant impact on our climate. Not only do they produce precipitation and provide shade from the sun, they also act as large reflectors that prevent the radiation of heat from the Earth – commonly known as the greenhouse effect.
“Although clouds have been studied for a long time, they are one of the biggest sources of uncertainty in climate models,” explains Bernhard Mehlig, Professor of Complex Systems at the University of Gothenburg. “This is because there are so many factors that determine how the clouds affect radiation. And the turbulence in the atmosphere means that everything is in constant motion. This makes things even more complicated.”
Focusing on the cloud edge
A scientific article in Physical Review Letters presents a new statistical model that describes how the number of water droplets, their sizes and the water vapour interact at the turbulent cloud edge. The distribution of water droplets is important because it affects how clouds reflect radiation.
“The model describes how the droplets shrink and grow at the cloud edge when turbulence mixes in drier air,” adds Johan Fries, a former doctoral student in physics and co-author of the study.
The researchers have identified the most important parameters, and have built their model accordingly. In brief, the model takes into account the laws of thermodynamics and the turbulent motion of the droplets. The model corresponds well with earlier numerical computer simulations, and explains their results.
The importance of evaporation
“But we’re still a long way from the finish line,” continues Professor Mehlig. “Our model is currently able to describe what is happening in one cubic metre of cloud. Say, fifteen years ago it was only one cubic centimetre, so we’re making progress.”
When policymakers discuss climate change, great importance is attached to IPCC climate models. However, according to the IPCC, the microphysical properties of clouds are among the least understood factors in climate science.
“Moreover, the evaporation of droplets is an important process, not only in the context of atmospheric clouds, but also within the field of infectious medicine. Tiny droplets that are produced when we sneeze can contain virus particles. If these droplets evaporate, the virus particles can remain in the air and infect others.”
Professor Mehlig has also co-authored another study that describes how solid particles, such as ice crystals, move within clouds.
“The ice crystals and the water droplets affect each other. But we don’t yet know how.”
New research published in the Journal of Orthopaedic Research suggests that the physical postures, breathing exercises, and mindfulness practices of yoga may benefit individuals with back pain.
In the study, 10 women with and 11 without chronic low back pain underwent an 8‐session yoga program over 4 weeks, with the first session conducted in a clinic and the rest delivered with a tele‐approach. Women with chronic low back pain experienced a significant decrease in pain intensity, as assessed through a 10-point visual analog scale (an average pain of 6.80 at the start, dropped to 3.30 after the sessions) and through a spine-related measure called the flexion–relaxation phenomenon, which is often absent or disrupted in people with low back pain (5.12 at the start versus 9.49 after the sessions).
The findings suggest yoga can positively impact the neuromuscular response during trunk flexion and pain perception in individuals with chronic low back pain.
“It was interesting to show the role that yoga might play in the management of chronic back pain,” said corresponding author Prof. Alessandro de Sire, MD, of the University of Catanzaro “Magna Graecia” and University Hospital “Renato Dulbecco,” in Italy.
The authors noted that further research is warranted to assess yoga’s long‐term effects.
Additional Information NOTE: The information contained in this release is protected by copyright. Please include journal attribution in all coverage. For more information or to obtain a PDF of any study, please contact: Sara Henning-Stout, newsroom@wiley.com.
About the Journal The Journal of Orthopaedic Research, a publication of the Orthopaedic Research Society, is the forum for the rapid publication of high quality reports of new information on the full spectrum of orthopaedic research, including life sciences, engineering, translational, and clinical studies.
About Wiley Wiley is a knowledge company and a global leader in research, publishing, and knowledge solutions. Dedicated to the creation and application of knowledge, Wiley serves the world’s researchers, learners, innovators, and leaders, helping them achieve their goals and solve the world's most important challenges. For more than two centuries, Wiley has been delivering on its timeless mission to unlock human potential. Visit us at Wiley.com. Follow us on Facebook, Twitter, LinkedIn and Instagram.
Renewable energy production leads to reduced carbon dioxide emissions in countries that are members of the Organization for Economic Co-operation and Development (OECD) but increased emissions in emerging economies, according to the results of a study published in the Natural Resources Forum. A similar disparity was seen when considering the environmental impacts of innovation. (The OECD is an international organization that works to build better policies for better lives. Thirty-eight countries around the world are currently members.)
Regarding institutional quality—the measure of the effectiveness and efficiency of a country’s institutions—higher quality was linked to fewer emissions in OECD countries but more carbon dioxide emissions in emerging economies. Furthermore, economic globalization improved environmental quality in OECD countries but worsened environmental quality in emerging economies.
Economic growth appeared to enhance environmental quality in both sets of countries.
“These findings provide valuable insights for shaping renewable energy policies, fostering innovation, promoting economic growth, enhancing institutional quality, and harnessing globalization efforts to reduce carbon dioxide emissions and enhance environmental quality,” the authors wrote.
Additional Information NOTE: The information contained in this release is protected by copyright. Please include journal attribution in all coverage. For more information or to obtain a PDF of any study, please contact: Sara Henning-Stout, newsroom@wiley.com.
About the Journal Natural Resources Forum, a United Nations Sustainable Development Journal, seeks to address gaps in current knowledge and stimulate relevant policy discussions, leading to the implementation of the sustainable development agenda and the achievement of the Sustainable Development Goals.
About Wiley Wiley is a knowledge company and a global leader in research, publishing, and knowledge solutions. Dedicated to the creation and application of knowledge, Wiley serves the world’s researchers, learners, innovators, and leaders, helping them achieve their goals and solve the world's most important challenges. For more than two centuries, Wiley has been delivering on its timeless mission to unlock human potential. Visit us at Wiley.com. Follow us on Facebook, Twitter, LinkedIn and Instagram.
A Comparative Study on The Moderating Impact of Renewable Energy and Innovation on Environmental Quality
ARTICLE PUBLICATION DATE
21-Feb-2024
Why are fish getting smaller as waters warm? It’s not their gills, finds study led by UMass Amherst
Biologists find no link between fish size and gill surface area—study suggests that models underlying some projections of future fisheries yields need to be reconsidered
AMHERST, Mass. – A collaborative team of scientists led by the University of Massachusetts Amherst recently found that there is no physiological evidence supporting a leading theory— which involves the surface area of fish gills —as to why many fish species are “shrinking” as waters grow warmer due to climate change. Known as the Gill Oxygen Limitation (GOL) theory, it has been proposed as the universal mechanism explaining fish size and has been used in some predictions of future global fisheries yields. However, the researchers, representing the National Oceanic and Atmospheric Administration, U.S. Geological Survey, the University of California Davis as well as UMass Amherst, conducted a series of long-term experiments on brook trout and found that, though increased temperatures do lead to significantly decreased body size, gill surface area did not explain the change. The results of the study were recently published in the Journal of Experimental Biology.
“We know that global climate change is happening and our oceans and rivers are getting warmer,” says Joshua Lonthair, lecturer in biology at UMass Amherst and the paper’s lead author. “And we know that many animals—not just fish—are growing to smaller adult body sizes under warmer temperatures. We even have a name for this, the Temperature Size Rule. But despite decades of research, we still don’t understand why size decreases as temperature increases.”
In both marine and freshwater fish species, rising water temperatures have a critical effect on metabolism, reproduction and other life functions, but a critical factor that most of the models underlying fisheries management rely on is fish size. Commercial fisheries are often regulated by tonnage, and when fish shrink, it takes more of them to fill out a ton. Lower weight is also linked to reduced reproduction. Altogether, this means that managers need to adjust their models for our changing world.
But how?
A leading theory, GOL, holds that fish growth is limited by how much oxygen gills can pull from the water. As the water warms, the biochemical processes of the fish speed up and require more oxygen. The GOL contends that gills have limited surface area that constrains the amount of oxygen they can supply, and thus, fish cannot grow as large under warm water conditions. Therefore, fish are “shrinking” to fit the limited oxygen that their gills can supply.
The GOL theory underlies widely cited model projections of drastic reductions in future global fisheries yields, including some used by the International Union for Conservation of Nature—but it has never been directly tested.
“We noticed that prior studies on GOL rely on data repurposed from other, unrelated research projects that weren’t designed to specifically to test the theory,” says Lisa Komoroske, assistant professor in environmental conservation at UMass Amherst and the paper’s senior author. “We designed a series of long-term experiments which collectively are the first effort to empirically test GOL.”
Specifically, Lonthair, Komoroske and their colleagues wanted to see how the three key ingredients of GOL—growth, energetic demands and the surface area of fish gills—changed as water temperatures increased. To do this they turned to brook trout, which are ideal test subjects: scientists already know a great deal about the species, they are fast-growing, economically and ecologically important to the Northeastern U.S. and they are comparatively easy to work with.
Once they had their test subjects—small fry that initially weighed between one and two grams each—they were placed into tanks, some of which contained normal, 15º Celsius water, and some of which contained water warmed to 20º Celsius. The fish were weighed and measured at the start of the experiment, and then monthly thereafter. Their oxygen consumption was also measured at two weeks, three months and six months, which is a way of ascertaining metabolic rate. Finally, the researchers collected gill samples from the same fish to measure changes in their gill surface area.
Once they began analyzing their data, a few things became clear: the brook trout in the warmer tanks were smaller, as expected, and in line with the Temperature Size Rule. However, the gill surface area was more than enough to meet the fishes’ energetic demands, which means that their growth was not limited by the surface area of the gills, as GOL predicts.
Furthermore, the team found that while the warm-tank fishes’ metabolic rates did increase at the three-month mark, by six months their oxygen rate returned to normal, suggesting that the fish could adjust their physiology over time to account for the increased water temperatures.
“Oxygen use may still be an important limiting factor in fish size,” says Lonthair, “but, taken together, our findings show that GOL cannot predict what we’re seeing, and this has implications for predicting climate impacts on future fisheries and ecosystems.”
“Our work highlights the importance of interdisciplinarity,” adds Komoroske. “Fisheries and macroecology scientists tend to work on the population and species level, while the physiologists tend to work on the individual and cellular levels. But these are academic distinctions, not natural ones, and if we’re going to help fish survive warming waters, we need to work across biological scales and join the insights of all these fields.”
So what is the mechanism governing fish size and temperature? “We don’t know yet,” says Lonthair. “And it may not be a single mechanism—it may be a host of factors, including oxygen use. We need more interdisciplinary long-term studies so that we can understand how best to adjust to our warming world.”
