Author: Futurity (National Geo)

Precise 3D imaging makes it possible to track radiation, used to treat half of all cancer patients, in real time.

By capturing and amplifying tiny sound waves created when X-rays heat tissues in the body, medical professionals can map the radiation dose within the body, giving them new data to guide treatments. It’s a first-of-its-kind view of an interaction doctors have previously been unable to “see.”

“Once you start delivering radiation, the body is pretty much a black box,” says Xueding Wang, professor of biomedical engineering and professor of radiology who leads the Optical Imaging Laboratory at the University of Michigan.

“We don’t know exactly where the X-rays are hitting inside the body, and we don’t know how much radiation we’re delivering to the target. And each body is different, so making predictions for both aspects is tricky,” says Wang, corresponding author of the study in Nature Biotechnology.

Radiation is used in treatment for hundreds of thousands of cancer patients each year, bombarding an area of the body with high energy waves and particles, usually X-rays. The radiation can kill cancer cells outright or damage them so that they can’t spread.

These benefits are undermined by a lack of precision, as radiation treatment often kills and damages healthy cells in the areas surrounding a tumor. It can also raise the risk of developing new cancers.

With real-time 3D imaging, doctors can more accurately direct the radiation toward cancerous cells and limit the exposure of adjacent tissues. To do that, they simply need to “listen.”

When X-rays are absorbed by tissues in the body, they are turned into thermal energy. That heating causes the tissue to expand rapidly, and that expansion creates a sound wave.

The acoustic wave is weak and usually undetectable by typical ultrasound technology. The new ionizing radiation acoustic imaging system detects the wave with an array of ultrasonic transducers positioned on the patient’s side. The signal is amplified and then transferred into an ultrasound device for image reconstruction.

With the images in-hand, an oncology clinic can alter the level or trajectory of radiation during the process to ensure safer and more effective treatments.

“In the future, we could use the imaging information to compensate for uncertainties that arise from positioning, organ motion, and anatomical variation during radiation therapy,” says first author Wei Zhang, a research investigator in biomedical engineering. “That would allow us to deliver the dose to the cancer tumor with pinpoint accuracy.”

Another benefit of the new technology is it can be easily added to current radiation therapy equipment without drastically changing the processes that clinicians are used to.

“In future applications, this technology can be used to personalize and adapt each radiation treatment to assure normal tissues are kept to a safe dose and that the tumor receives the dose intended,” says Kyle Cuneo, associate professor of radiation oncology at Michigan Medicine.

“This technology would be especially beneficial in situations where the target is adjacent to radiation sensitive organs such as the small bowel or stomach.”

The University of Michigan has applied for patent protection and is seeking partners to help bring the technology to market. The National Cancer Institute and the Michigan Institute for Clinical and Health Research supported the work.

Source: University of Michigan

Mass coral bleaching events make it harder for some species of reef fish to identify competitors, new research reveals.

Scientists studying reefs across five Indo-Pacific regions found that the ability of butterfly fish individuals to identify competitor species and respond appropriately was compromised after widespread loss of coral caused by bleaching.

This change means they make poorer decisions that leave them less able to avoid unnecessary fights, using up precious limited energy. The scientists believe this increases the likelihood of coral loss.

“By recognizing a competitor, individual fish can make decisions about whether to escalate, or retreat from, a contest—conserving valuable energy and avoiding injuries,” says lead author Sally Keith, a senior lecturer in marine biology at Lancaster University.

“These rules of engagement evolved for a particular playing field, but that field is changing. Repeated disturbances, such as bleaching events, alter the abundance and identity of corals—the food source of butterfly fish. It’s not yet clear whether these fish have the capacity to update their rule book fast enough to recalibrate their decisions.”

“The impacts of global change on biodiversity are increasingly obvious,” says coauthor Nate Sanders, a professor in the ecology and evolutionary biology department at the University of Michigan. “This work highlights the importance of studying the behavioral responses of individuals in light of global change.”

For the study in Proceedings of the Royal Society B, the researchers took more than 3,700 observations of 38 species of butterfly fish on reefs before and after coral bleaching events and compared their behaviors.

After coral mortality caused by the bleaching event, signaling between fish of different species was less common, with encounters escalating to chases in more than 90% of cases—up from 72% before the event. Researchers also found the distance of these chases increased following bleaching, with fish expending more energy chasing away potential competitors than they would have done previously.

The researchers believe the environmental disturbances are affecting fish recognition and responses because the bleaching events, in which many corals die, are forcing fish species to change and diversify their diets and territories. Therefore, these large-scale environmental changes are disrupting long-established and co-evolved relationships that allow multiple fish species to coexist.

“We know that biodiversity is being lost—species are vanishing and populations are declining,” Sanders says. “Perhaps by focusing more on how the behavior of individuals responds to global change, we can start to predict how biodiversity might change in the future. And better yet, try to do something about it.”

Additional coauthors are from Lancaster University and the University of Queensland. The Natural Environment Research Council, the Australian Research Council, and the Villum Foundation funded the work.

Source: University of Michigan

Animals are crucial to reforestation, research finds.

And yet, the world’s wildlife populations have declined by almost 70% in the last 50 years as humans have destroyed and polluted habitats.

Efforts to restore forests have often focused on trees, but a new study in the journal Philosophical Transactions that animals play a key role in the recovery of tree species by carrying a wide variety of seeds into previously deforested areas.

Sergio Estrada-Villegas, a postdoctoral associate at the Yale School of the Environment, led the study with Liza Comita, professor of tropical forest ecology. The project examines a series of regenerating forests in central Panama spanning 20 to 100 years post-abandonment.

“When we talk about forest restoration, people typically think about going out and digging holes and planting seedlings,” Comita says. “That’s actually not a very cost-effective or efficient way to restore natural forests. If you have a nearby preserved intact forest, plus you have your animal seed dispersers around, you can get natural regeneration, which is a less costly and labor-intensive approach.”

The research team analyzed a unique, long-term data set from the forest in Barro Colorado Nature Monument in Panama, which the Smithsonian Tropical Research Institute oversees, to compare what proportion of tree species in forests were dispersed by animals or other methods, like wind or gravity, and how that changes over time as the forest ages. The team focused on the proportion of plants dispersed by four groups of animals: flightless mammals, large birds, small birds, and bats.

Because the area has been intensely studied by biologists at the Smithsonian for about a century, the research team was able to delve into data stemming back decades, including aerial photographs taken in the 1940s-1950s. The area also presents a unique view into forests where there is very little hunting or logging. The results offer the most detailed data of animal seed dispersal across the longest time frame of natural restoration, according to the study.

The role of flightless animals in seed dispersal across all forest ages, from 20 years to old growth, and the variety of animal species involved were among the most important findings of the study and point to the importance of natural regeneration of forests, Comita and Estrada-Villegas say. In tropical forests, more than 80% of tree species can be dispersed by animals.

The researchers say the findings can serve as a road map for natural regeneration of forests that preserve biodiversity and capture and store carbon at a time when the UN Decade of Restoration is highlighting the need for land conservation, and world leaders are working to mitigate climate change stemming from fossil fuel emissions.

Forests soak up carbon dioxide from the atmosphere and store it in biomass and soils. Tropical forests, in particular, play an important role in regulating global climate and supporting high plant and animal diversity, the researchers note.

Estrada-Villegas, an ecologist who studies both bats and plants, says the study highlights how crucial animals are to healthy forests.

“In these tropical environments, animals are paramount to a speedy recovery of forests,” says Estrada-Villegas.

Coauthors are from the Max Planck Institute for Animal Behavior; the Universidad de los Andes in Bogota, Columbia; the Smithsonian Tropical Research Institute in Balboa, Panama; and Clemson University.

Source: Yale University

A warming climate will increase the number of tropical cyclones and their intensity in the North Atlantic, potentially creating more and stronger hurricanes, according to simulations using a high-resolution, global climate model.

“Unfortunately, it’s not great news for people living in coastal regions,” says Christina Patricola, an Iowa State University assistant professor of geological and atmospheric sciences, an affiliate of the US Department of Energy’s Lawrence Berkeley National Laboratory in California, and a study leader.

“Atlantic hurricane seasons will become even more active in the future, and hurricanes will be even more intense,” Patricola says.

The researchers ran climate simulations using the Department of Energy’s Energy Exascale Earth System Model and found that tropical cyclone frequency could increase 66% during active North Atlantic hurricane seasons by the end of this century.

Those seasons are typically characterized by La Niña conditions—unusually cool surface water in the eastern tropical Pacific Ocean—and the positive phase of the Atlantic Meridional Mode—warmer surface temperatures in the northern tropical Atlantic Ocean.

The projected numbers of tropical cyclones could increase by 34% during inactive North Atlantic hurricane seasons. Inactive seasons generally occur during El Niño conditions with warmer surface temperatures in the eastern tropical Pacific Ocean and the negative phase of the Atlantic Meridional Mode with cooler surface temperatures in the northern tropical Atlantic Ocean.

In addition, the simulations project an increase in storm intensity during the active and inactive storm seasons.

“Altogether, the co-occurring increase in (tropical cyclone) number and strength may lead to increased risk to the continental North Atlantic in the future climate,” the researchers write.

Patricola adds: “Anything that can be done to curb greenhouse gas emissions could be helpful to reduce this risk.”

What are North Atlantic tropical cyclones? “Tropical cyclone is a more generic term than hurricane,” Patricola says. “Hurricanes are relatively strong tropical cyclones.”

Exactly, says the National Oceanic and Atmospheric Administration. Tropical cyclone is a general reference to a low-pressure system that forms over tropical waters with thunderstorms near the center of its closed, cyclonic winds. When those rotating winds exceed 39 MPH, the system becomes a named tropical storm. At 74-plus MPH, it becomes a hurricane in the Atlantic and East Pacific oceans, a typhoon in the northern West Pacific.

Patricola and another group of collaborators have also published a second research paper about tropical cyclones, also in Geophysical Research Letters. The paper examines a possible explanation for the relatively constant number of tropical cyclones observed globally from year to year.

Could it be that African Easterly Waves, low pressure systems over the Sahel region of North Africa that take moist tropical winds and raise them up into thunderclouds, are a key to that steady production of storms?

Using regional model simulations, the researchers were able to filter out the African Easterly Waves and see what happened.

As it turned out, the simulations didn’t change the seasonal number of Atlantic tropical cyclones. But, tropical cyclones were stronger, peak formation of the storms shifted from September to August, and the formation region shifted from the coast of North Africa to the Gulf of Mexico.

So African Easterly Waves many not help researchers predict the number of Atlantic tropical cyclones every year, but they do appear to affect important storm characteristics, including intensity and possibly where they make landfall.

Both papers call for more study.

“We are,” Patricola says, “chipping away at the problem of predicting the number of tropical cyclones.”

Source: Iowa State University

Women in Sub-Saharan Africa who experience recent intimate partner violence are three times more likely to contract HIV, according to new research.

“Worldwide, more than one in four women experience intimate partner violence in their lifetime,” says McGill University Professor Mathieu Maheu-Giroux, a Canada Research Chair in Population Health Modeling.

“Sub-Saharan Africa is among one of the regions in the world with the highest prevalence of both IPV and HIV. We wanted to examine the effects of intimate partner violence on recent HIV infections and women’s access to HIV care in this region,” he says.

Their study, published in The Lancet HIV, shows considerable overlap between violence against women and the HIV epidemics in some of the highest burdened countries. Among women living with HIV, those experiencing intimate partner violence were 9% less likely to achieve viral load suppression—the ultimate step in HIV treatment.

“The 2021 UN General Assembly, attended and supported by the Government of Canada, adopted the Political Declaration on HIV and AIDS with bold new global targets for 2025. This encompasses a commitment to eliminate all forms of sexual and gender-based violence, including IPV, as a key enabler of the HIV epidemic. Improving our understanding of the relationships between IPV and HIV is essential to meet this commitment,” says Maheu-Giroux.

The researchers found that physical or sexual intimate partner violence in the past year was associated with recent HIV acquisition and less frequent viral load suppression. According to the researchers, IPV could also pose barriers for women in getting HIV care and remaining in care while living with the virus.

“Given the high burden of IPV worldwide, including in Canada, the need to stem the mutually reinforcing threats of IPV and HIV on women’s health and well-being is urgent,” says Salome Kuchukhidze, a PhD candidate studying epidemiology and the lead author of the research.

Source: McGill University

A semi-submersible vehicle may prove that the best way to travel undetected and efficiently in water is not on top, or below, but in between.

The roughly 1.5-foot-long semi-sub prototype, built with off-the-shelf and 3D-printed parts, showed its seaworthiness in water tests, moving quickly with low drag and a low profile.

The researchers detailed the test results in a study in the journal Unmanned Systems.

This vessel-type isn’t new. Authorities have discovered crudely made semi-subs being used for illicit purposes in recent years, but researchers aim to demonstrate how engineer-developed half-submerged vessels can efficiently serve military, commercial, and research purposes.

“A semi-submersible vehicle is relatively inexpensive to build, difficult to detect, and it can go across oceans,” says Konstantin Matveev, a professor of engineering at Washington State University who led the work.

“It’s not so susceptible to waves in comparison to surface ships since most of the body is underwater, so there are some economic advantages as well.”

Since the semi-sub sails mostly at the water line, it does not need to be made of as strong materials as a submarine which has to withstand the pressure of being underwater for long periods of time. The semi-sub also has the advantage of having a small platform in contact with the atmosphere, making it easier to receive and transmit data.

For this study, Matveev and coauthor Pascal Spino, a recent Washington State graduate, piloted the semi-sub in Snake River’s Wawawai Bay in Washington state. They tested its stability and ability to maneuver.

The semi-sub reached a max speed of 1.5 meters per second (roughly 3.4 miles an hour), but at higher speeds, it rises above the water creating more of a wake and expending more energy. At lower speeds, it is almost fully immersed and barely makes a ripple.

The researchers also outfitted the semi-sub with sonar and mapped the bottom of a reservoir near Pullman, Washington to test its ability to collect and transmit data.

While not yet completely autonomous, the semi-sub can be pre-programmed to behave in certain ways, such as running a certain route by itself or responding to particular objects by pursuing them or running away.

While the semi-sub is relatively small at 450 mm long with a 100 mm diameter (about 1.5 foot long and 4 inches in diameter), Matveev says it is possible for larger semi-subs to be built to carry significant cargo. For instance, they could be used to help refuel ships or stations at sea. They could even be scaled up to rival container ships, and since they experience less drag in the water, they would use less fuel creating both an environmental and economic advantage.

For now, Matveev’s lab is continuing work on optimizing the shape of semi-submersible vehicle prototypes to fit specific purposes. He is currently collaborating with the US Naval Academy in Annapolis, Maryland to work on the vehicles’ operational capabilities and compare numerical simulations with results from experiments.

Source: Washington State University

A new type of active pixel sensor that uses a novel 2D-material may enable ultra-sharp cell phone photos and create a new class of extremely energy-efficient Internet of Things sensors, researchers say.

“When people are looking for a new phone, what are the specs that they are looking for?” says Saptarshi Das, associate professor of engineering science and mechanics at Penn State and lead author of the paper in Nature Materials.

“Quite often, they are looking for a good camera, and what does a good camera mean to most people? Sharp photos with high resolution.”

Most people just snap a photo of a friend, a family gathering, or a sporting event, and never think about what happens “behind the scenes” inside the phone when one snaps a picture. There is quite a bit happening to enable you to see a photo right after you take it, and this involves image processing, Das says.

“When you take an image, many of the cameras have some kind of processing that goes on in the phone, and in fact, this sometimes makes the photo look even better than what you are seeing with your eyes. These next generation of phone cameras integrate image capture with image processing to make this possible, and that was not possible with older generations of cameras.”

However, the great photos in the newest cameras have a catch—the processing requires a lot of energy.

“There’s an energy cost associated with taking a lot of images,” says Akhil Dodda, a graduate research assistant at Penn State at the time of the study who is now a research staff member at Western Digital, and co-first author of the study.

“If you take 10,000 images, that is fine, but somebody is paying the energy costs for that. If you can bring it down by a hundredfold, then you can take 100 times more images and still spend the same amount of energy. It makes photography more sustainable so that people can take more selfies and other pictures when they are traveling. And this is exactly where innovation in materials comes into the picture.”

Low light phone photos

The innovation in materials outlined in the study revolves around how the researchers added in-sensor processing to active pixel sensors to reduce their energy use. So, they turned to a novel 2D material, which is a class of materials only one or a few atoms thick, molybdenum disulfide. It is also a semiconductor and sensitive to light, which makes it ideal as a potential material to explore for low-energy in-sensor processing of images.

“We found that molybdenum disulfide has very good photosensitive response,” says Darsith Jayachandran, graduate research assistant in engineering and mechanics and co-first author of the study. “From there, we tested it for the other properties we were looking for.”

These properties included sensitivity to low light, which is important for the dynamic range of the sensor. The dynamic range refers to the ability to “see” objects in both low light such as moonlight and bright light such as sunlight. The human eye can see stars at night better than most cameras due to having superior dynamic range.

Molybdenum disulfide also demonstrated strong signal conversion, charge-to-voltage conversion and data transmission capabilities. This makes the material an ideal candidate to enable an active pixel sensor that can do both light sensing and in-sensor image processing.

“From there, we put the sensors into an array,” Jayachandran says. “There are 900 pixels in a nine square millimeter array we developed, and each pixel is about 100 micrometers. They are much more sensitive to light than current CMOS sensors, so they do not require any additional circuitry or energy use. So, each pixel requires much less energy to operate, and this would mean a better cell phone camera that uses a lot less battery.”

Internet of Things benefits

The dynamic range and image processing would enable users to take sharp photos in a variety of adverse conditions for photography, according to Das.

“For example, you could take clearer photos of friends outside at night or on a rainy or foggy day,” Das says. “The camera could do denoising to clear up the fog and the dynamic range would enable say a night photo of a friend with stars in the background.”

Along with enabling a top-rate phone camera in the future, the team also envisions their improved sensor technology could have other applications. This would include better light sensors for Internet of Things (IoT) and Industry 4.0 applications.

Industry 4.0 is the term for a growing movement that combines traditional industry practices and cutting-edge digital technology such as the Internet of Things, cloud data storage, and artificial intelligence/machine learning. The goal is to improve manufacturing by developing more efficient processes and practices through intelligent automation, and sensors are key.

“Sensors that can see through machines while in operation and identify defects are very important in the IoT,” Dodda says. “Conventional sensors consume a lot of energy so that is a problem, but we developed an extremely energy efficient sensor that enables better machine learning, etc. and saves a lot in energy costs.”

The Department of Defense and the National Science Foundation supported the work.

Source: Penn State

Does COVID change the body’s response to other threats? Depends on your sex, research indicates.

The long-term effects of infection on the immune system have long intrigued immunobiologist John Tsang. After the body has faced down a pathogen, does the immune system return to the previous baseline? Or does a single infection change it in ways that alter how it will respond not only to a familiar virus but also to the next new viral or bacterial threat it faces?

Tsang, a professor of immunobiology and biomedical engineering at Yale University, has long believed that the immune system reverts to the previous stable baseline after viral infection.

The emergence of the COVID-19 pandemic in 2020 allowed him and colleagues to test that theory. The answer, they find, depends on the individual’s sex, according to a study in the journal Nature.

For the study, a team led by Tsang, who at the time was at the National Institute of Allergy and Infectious Diseases (NIAID), and colleagues, including lead author Rachel Sparks, also from NIAID, systematically analyzed immune responses of healthy people who had received the flu vaccine. From that data, they then compared the responses between those who had never been infected by SARS-CoV-2, the virus that causes COVID-19, and those who experienced mild cases but recovered.

To their surprise, they found that the immune systems of men who had recovered from mild cases of COVID-19 responded more robustly to flu vaccines than women who had had mild cases or men and women who had never been infected.

In essence, the baseline immune statuses in men previously infected with SARS-CoV-2 was altered in ways that changed the response to an exposure different from SARS-CoV-2, the authors say.

“This was a total surprise,” Tsang says. “Women usually mount a stronger overall immune response to pathogens and vaccines, but are also more likely to suffer from autoimmune diseases.”

The findings may also be linked to an observation made early in the pandemic: Men were much more likely to die from a runaway immune response than women after contracting the COVID-19 virus. Even mild cases of COVID-19, the new findings suggest, might trigger stronger inflammatory responses in males than females, resulting in more pronounced functional changes to the male immune system, even long after recovery.

Their unbiased analysis of immune system status down to the individual cell level reveals several differences between COVID-recovered males and healthy controls and COVID-recovered females, both before and after receiving flu vaccinations. For instance, previously infected males produced more antibodies to influenza and produced increased levels of interferons, which are produced by cells in response to infections or vaccines. Generally, healthy females have stronger interferon responses than their male counterparts.

Understanding the lingering effects of COVID-19 on the immune system is crucial, the authors say, since more than 600 million people worldwide have been infected so far, and the emergence of “long-COVID” symptoms in some people continues to be a major health concern.

“Our findings point to the possibility that any infection or immune challenge may change the immune status to establish new set points,” says Sparks. “The immune status of an individual is likely shaped by a multitude of prior exposures and perturbations.”

Tsang thinks these findings may also help scientists create better vaccines against diverse threats by, for instance, mimicking how mild COVID-19 changes the male immune baseline.

Source: Yale University

Genetically engineered mitochondria can convert light energy into chemical energy that cells can use, ultimately extending the life of the roundworm C. elegans, a new study shows.

While the prospect of sunlight-charged cells in humans is more science fiction than science, the research, which takes a page from the field of renewable energy, sheds light on important mechanisms in the aging process.

“We know that mitochondrial dysfunction is a consequence of aging,” says Andrew Wojtovich, associate professor of anesthesiology and perioperative medicine and pharmacology and physiology at the University of Rochester Medical Center, as well as senior author of the study in Nature Aging.

“This study found that simply boosting metabolism using light-powered mitochondria gave laboratory worms longer, healthier lives. These findings and new research tools will enable us to further study mitochondria and identify new ways to treat age-related diseases and age healthier.”

Mitochondria are organelles found in most cells in the body. Often referred to as cellular power plants, mitochondria use glucose to produce adenosine triphosphate (ATP), the compound that provides energy for key functions in the cell, such as muscle contraction and the electrical impulses that help nerve cells communicate with each other.

Production of ATP is the result of a number of reactions made possible by the exchange of protons across a membrane that separates different compartments in mitochondria, the efficiency with which this occurs is called membrane potential. Known to decline with age, membrane potential is a topic of great interest in the scientific community because of its potential role in a number of age-related diseases, such as neurodegenerative disorders.

The new research involved C. elegans, a microscopic roundworm that—like the fruit fly Drosophila—has long been a research tool used by scientists to understand basic biological principles that, in many cases, apply throughout the animal kingdom.

To carry out the experiments, a team of researchers turned to optogenetics, a research tool that uses light to control biological processes within cells. Neuroscientists use optogenetics to target and activate specific neurons to study patterns of brain activity. The tool allowed the researchers to target and manipulate activity in C. elegans mitochondria—a task made easier by the fact that the worms are transparent.

The researchers genetically engineered C. elegans mitochondria to include a light-activated proton pump obtained from a fungus, an achievement the team first described in a 2020 paper in the journal EMBO Reports.

In the new study, when exposed to light, the proton pumps moved charged ions across the membrane, using the energy from the light to charge the mitochondria. This process, which the researchers dubbed mitochondria-ON (mtON), increased membrane potential and ATP production, and resulted in a 30-40% increase in lifespan of the roundworms.

“Mitochondria are similar to industrial power plants in that they combust a source of carbon, primarily glucose, to produce useful energy for the cell,” says first author Brandon Berry, who received his doctoral degree in physiology from the University of Rochester and is now a postdoctoral scholar at the University of Washington.

“What we have done is essentially hooked up a solar panel to the existing power plant infrastructure. In this instance, the solar panel is the optogenetic tool mtON. The normal mitochondrial machinery is then able to harness the light energy to provide the ATP in addition to the normal combustion pathway.”

The study is important because it provides researchers with more insight into the complex biological roles that mitochondria play in the human body, a topic that the scientific community is only now beginning to understand. The study also creates a new method to manipulate and study mitochondria in the environment of a living cell. This could serve as an important platform to study mitochondria and identify ways to intervene and support function.

“We need to understand more about how mitochondria truly behave in an animal,” says Berry. “First in worms, like the current study, but then in human cells in culture and in rodents. That way future research will be well informed to target the most likely players in human disease and aging.”

Additional coauthors are from the University of Rochester; the University of Washington; and the Research Institute for Farm Biology and Technical University of Munich, both in Germany. The National Institutes of Health and a Longevity Impetus Grant funded the work.

Source: University of Rochester

Researchers have created a map of oceanic “dead zones” that existed during the Pliocene epoch, when the Earth’s climate was two to three degrees warmer than it is now.

The work could provide a glimpse into the locations and potential impacts of future low oxygen zones in a warmer Earth’s oceans.

Oxygen minimum zones, or OMZs, are areas in the ocean where oxygen levels in the mid-waters (from 100 to 1,000 meters below the surface) are too low to support most marine life. These dead zones play an important role in the ocean’s overall health.

“OMZs are very important for geochemical cycling in the ocean,” says Catherine Davis, assistant professor of marine, earth and atmospheric sciences at North Carolina State University and corresponding author of the research in Nature Communications.

“They occur in areas where sunlight and atmospheric oxygen don’t reach. Their locations dictate where carbon and nitrogen (an essential nutrient for all life on Earth) are available in the ocean—so they’re important drivers of nutrient cycles.”

Being able to predict the location of OMZs is important not only for understanding nutrient cycling, but also because of their effects on marine life. Oceanic dead zones restrict the range of animals to the shallow surface ocean where oxygen is more plentiful.

Davis and her colleagues wanted to figure out how a warmer climate might impact future OMZs. So they looked to the Pliocene epoch, (5.3 to 2.6 million years ago) when the Earth’s atmospheric CO2 levels were close to what they are now.

“The Pliocene is the last time that we had a stable, warm climate globally, and the average global temperature was 2 C to 3 C warmer than it is now—which is what scientists predict could be the case in about 100 years,” Davis says.

To determine where Pliocene OMZs were located, the researchers used tiny fossilized plankton called foraminifera. Foraminifera are single-celled organisms about the size of a large grain of sand. They form hard, calcium carbonate shells, which can stay in marine sediments.

One species in particular—Globorotaloides hexagonus—is found only in low oxygen zones. By combing through databases of Pliocene sediments to locate that species, the team was able to map Pliocene OMZs. They overlaid their map onto a computer model of Pliocene oxygen levels, and found that the two agreed with each other.

The OMZ map shows that during the Pliocene, low-oxygen waters were much more widespread in the Atlantic Ocean—particularly in the North Atlantic. The North Pacific, on the other hand, had fewer low-oxygen areas.

“This is the first global spatial reconstruction of oxygen minimum zones in the past,” Davis says. “And it’s in line with what we’re already seeing in the Atlantic in terms of lower oxygen levels. Warmer water holds less oxygen. This dead zone map from the Pliocene could give us a glimpse into what the Atlantic might look like 100 years from now on a warmer Earth.”

What would a future with much less oxygen in the Atlantic mean? According to Davis, it could have a big impact on everything from carbon storage and nutrient cycling in the ocean to how fisheries and marine species are managed.

“OMZs act as a ‘floor’ for marine animals—they get squished to the surface,” Davis says. “So fishermen may suddenly see a lot of fish, but it doesn’t mean that there are actually more than normal—they’re just being forced into a smaller space. Fisheries will need to take the effects of OMZs into account when managing populations.

“We may also see subtle but far-reaching changes concerning the amounts of nutrients available for life in those surface waters, as well as where CO2 taken up by the ocean is stored.”

Davis began the research while a postdoctoral researcher at Yale University. Additional coauthors are from Yale, George Mason University, NASA, and NC State.

The National Science Foundation supported the work.

Source: NC State