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)
Saturday, July 17, 2021
US corn and soybean maladapted to climate variations, study shows
UNIVERSITY OF ILLINOIS COLLEGE OF AGRICULTURAL, CONSUMER AND ENVIRONMENTAL SCIENCES
IMAGE: MADHU KHANNA AND CHENGZHENG YU, DEPARTMENT OF AGRICULTURAL AND CONSUMER ECONOMICS, UNIVERSITY OF ILLINOIS, STUDIED CORN AND SOYBEAN ADAPTATION TO CLIMATE VARIATIONS IN THE U.S. view more
CREDIT: LAURA MABRY, COLLEGE OF ACES, UNIVERSITY OF ILLINOIS.
URBANA, Ill. - U.S. corn and soybean varieties have become increasingly heat and drought resistant as agricultural production adapts to a changing climate. But the focus on developing crops for extreme conditions has negatively affected performance under normal weather patterns, a University of Illinois study shows.
"Since the 1950s, advances in breeding and management practices have made corn and soybean more resilient to extreme heat and drought. However, there is a cost for it. Crop productivity with respect to the normal temperature and precipitation is getting lower," says Chengzheng Yu, doctoral student in the Department of Agricultural and Consumer Economics (ACE) at the University of Illinois and lead author on the new paper, published in Scientific Reports.
Climate projections indicate a mix of extreme and normal weather patterns in the next 50 years, so crops must perform well under a variety of conditions, explains study co-author Madhu Khanna, ACES distinguished professor of environmental economics in ACE.
"It is not enough to just focus on extreme weather conditions. We can't look at the impacts of climate change in a piecemeal fashion and develop varieties only to cope with certain aspects of it," Khanna states.
Yu, Khanna, and co-author Ruiqing Miao, Auburn University, studied corn and soybean yield from 1951 to 2017 in the eastern part of the U.S., an area where crops can grow without irrigation. Crop yield increased significantly during this period due to a wide range of technological and breeding improvements. But when the researchers isolated the effect of climate-related adaptations, they found significant negative impacts on yield.
While heat and drought tolerance increased yield by 33% for corn and 20% for soybean over this period, the gain was offset by reduced productivity under normal conditions. Overall, maladaptation due to climate-related factors reduced corn and soybean yield by 8% and 67%, respectively, the researchers found.
"There's been this trade-off; crops become better adapted to extreme weather, but less adapted to normal conditions," Khanna says. "Overall, crop yields went up by 100% to 200% over the past decades. We break this down into the components that happened because of climate-related changes, and components that happened irrespective of climate change. And we find the impact of climate-related adaptation has been negative," she explains.
The researchers also projected net effects of climate change adaptation on crop yields by 2050 under a range of warming scenarios. In the most extreme scenarios, weather-adapted variations will perform better. But under less extreme scenarios varieties that perform well in normal climate would be more productive.
Khanna and Yu conclude that crop breeders should focus on developing crop varieties for diverse weather patterns. Flexibility is important for agricultural producers to be well prepared for future conditions.
"There will be a very significant reduction in crop yield for both corn and soybean over the next 50 years under some extreme warming scenarios, even though the crops are supposedly adapted to extreme conditions. There's overall maladaptation, because the crops are not fully adapted to every possible combination of extreme and normal conditions. And the overall impact is going to be very negative," Khanna says. "We need to drastically change how we're adapting our crops so that they're better prepared for the mix of conditions we are likely to encounter in the following years."
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The Department of Agricultural and Consumer Economics is in the College of Agricultural, Consumer and Environmental Sciences, University of Illinois.
The paper, "Maladaptation of U.S. corn and soybeans to a changing climate," is published in Nature Scientific Reports. [https://doi.org/10.1038/s41598-021-91192-5]. Authors are Chengzheng Yu, Ruiqing Miao, and Madhu Khanna.
Funding for this research was provided by a USDA National Institute of Food and Agriculture Hatch grant.
BERNIE SANDERS STATE
Invention: The Storywrangler
Vermont scientists create tool to explore billions of social media messages, potentially predict political and financial turmoil
IMAGE: UVM SCIENTISTS HAVE INVENTED A NEW TOOL: THE STORYWRANGLER. IT VISUALIZES THE USE OF BILLIONS OF WORDS, HASHTAGS AND EMOJI POSTED ON TWITTER. IN THIS EXAMPLE FROM THE TOOL'S ONLINE... view more
CREDIT: UVM
For thousands of years, people looked into the night sky with their naked eyes -- and told stories about the few visible stars. Then we invented telescopes. In 1840, the philosopher Thomas Carlyle claimed that "the history of the world is but the biography of great men." Then we started posting on Twitter.
Now scientists have invented an instrument to peer deeply into the billions and billions of posts made on Twitter since 2008 -- and have begun to uncover the vast galaxy of stories that they contain.
"We call it the Storywrangler," says Thayer Alshaabi, a doctoral student at the University of Vermont who co-led the new research. "It's like a telescope to look -- in real time -- at all this data that people share on social media. We hope people will use it themselves, in the same way you might look up at the stars and ask your own questions."
The new tool can give an unprecedented, minute-by-minute view of popularity, from rising political movements to box office flops; from the staggering success of K-pop to signals of emerging new diseases.
The story of the Storywrangler -- a curation and analysis of over 150 billion tweets--and some of its key findings were published on July 16 in the journal Science Advances.
EXPRESSIONS OF THE MANY
The team of eight scientists who invented Storywrangler -- from the University of Vermont, Charles River Analytics, and MassMutual Data Science -- gather about ten percent of all the tweets made every day, around the globe. For each day, they break these tweets into single bits, as well as pairs and triplets, generating frequencies from more than a trillion words, hashtags, handles, symbols and emoji, like "Super Bowl," "Black Lives Matter," "gravitational waves," "#metoo," "coronavirus," and "keto diet."
"This is the first visualization tool that allows you to look at one-, two-, and three-word phrases, across 150 different languages, from the inception of Twitter to the present," says Jane Adams, a co-author on the new study who recently finished a three-year position as a data-visualization artist-in-residence at UVM's Complex Systems Center.
The online tool, powered by UVM's supercomputer at the Vermont Advanced Computing Core, provides a powerful lens for viewing and analyzing the rise and fall of words, ideas, and stories each day among people around the world. "It's important because it shows major discourses as they're happening," Adams says. "It's quantifying collective attention." Though Twitter does not represent the whole of humanity, it is used by a very large and diverse group of people, which means that it "encodes popularity and spreading," the scientists write, giving a novel view of discourse not just of famous people, like political figures and celebrities, but also the daily "expressions of the many," the team notes.
In one striking test of the vast dataset on the Storywrangler, the team showed that it could be used to potentially predict political and financial turmoil. They examined the percent change in the use of the words "rebellion" and "crackdown" in various regions of the world. They found that the rise and fall of these terms was significantly associated with change in a well-established index of geopolitical risk for those same places.
WHAT'S HAPPENING?
The global story now being written on social media brings billions of voices -- commenting and sharing, complaining and attacking -- and, in all cases, recording -- about world wars, weird cats, political movements, new music, what's for dinner, deadly diseases, favorite soccer stars, religious hopes and dirty jokes.
"The Storywrangler gives us a data-driven way to index what regular people are talking about in everyday conversations, not just what reporters or authors have chosen; it's not just the educated or the wealthy or cultural elites," says applied mathematician Chris Danforth, a professor at the University of Vermont who co-led the creation of the StoryWrangler with his colleague Peter Dodds. Together, they run UVM's Computational Story Lab.
"This is part of the evolution of science," says Dodds, an expert on complex systems and professor in UVM's Department of Computer Science. "This tool can enable new approaches in journalism, powerful ways to look at natural language processing, and the development of computational history."
How much a few powerful people shape the course of events has been debated for centuries. But, certainly, if we knew what every peasant, soldier, shopkeeper, nurse, and teenager was saying during the French Revolution, we'd have a richly different set of stories about the rise and reign of Napoleon. "Here's the deep question," says Dodds, "what happened? Like, what actually happened?"
GLOBAL SENSOR
The UVM team, with support from the National Science Foundation, is using Twitter to demonstrate how chatter on distributed social media can act as a kind of global sensor system -- of what happened, how people reacted, and what might come next. But other social media streams, from Reddit to 4chan to Weibo, could, in theory, also be used to feed Storywrangler or similar devices: tracing the reaction to major news events and natural disasters; following the fame and fate of political leaders and sports stars; and opening a view of casual conversation that can provide insights into dynamics ranging from racism to employment, emerging health threats to new memes.
In the new Science Advances study, the team presents a sample from the Storywrangler's online viewer, with three global events highlighted: the death of Iranian general Qasem Soleimani; the beginning of the COVID-19 pandemic; and the Black Lives Matter protests following the murder of George Floyd by Minneapolis police. The Storywrangler dataset records a sudden spike of tweets and retweets using the term "Soleimani" on January 3, 2020, when the United States assassinated the general; the strong rise of "coronavirus" and the virus emoji over the spring of 2020 as the disease spread; and a burst of use of the hashtag "#BlackLivesMatter" on and after May 25, 2020, the day George Floyd was murdered.
"There's a hashtag that's being invented while I'm talking right now," says UVM's Chris Danforth. "We didn't know to look for that yesterday, but it will show up in the data and become part of the story."
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CTHULHU STUDIES
3D printed replicas reveal swimming capabilities of ancient cephalopods
Experiments in water tanks, including a U pool, suggest the ancient animals lived a vertical marine lifestyle
IMAGE: RECONSTRUCTION OF THE ORTHOCONE AMMONITE, BACULITES COMPRESSUS. view more
CREDIT: DAVID PETERMAN
University of Utah paleontologists David Peterman and Kathleen Ritterbush know that it's one thing to use math and physics to understand how ancient marine creatures moved through the water. It's another thing to actually put replicas of those creatures into the water and see for themselves. They're among the scientists who are, through a range of methods including digital models and 3-D printed replicas, "de-fossilizing" animals of the past to learn how they lived.
Peterman, Ritterbush and their colleagues took 3-D printed reconstructions of fossil cephalopods to actual water tanks (including a University of Utah swimming pool) to see how their shell structure may have been tied to their movement and lifestyle. Their research is published in PeerJ and in an upcoming memorial volume to the late paleontologist William Cobban. They found that cephalopods with straight shells called orthocones likely lived a vertical life, jetting up and down to catch food and evade predators. Others with spiral shells, called torticones, added a gentle spin to their vertical motions.
"Thanks to these novel techniques," says Peterman, a postdoctoral scholar in the Department of Geology and Geophysics, "we can trudge into a largely unexplored frontier in paleobiology. Through detailed modeling, these techniques help paint a clearer picture of the capabilities of these ecologically significant animals while they were alive."
The researchers are veterans of this style of "virtual paleontology," having worked with digital ammonoid models and 3-D printed versions to test hypotheses about their evolution and lifestyles. Most ammonoids have coiled shells, like today's chambered nautilus, and darted around the ocean in all directions.
But in their researcher published in PeerJ, Peterman and Ritterbush, assistant professor of Geology & Geophysics, explored a different shell shape--the straight-shelled orthocone. Straight shells evolved several times in different lineages throughout the fossil record, suggesting they had some adaptive value.
"This is important because orthocones span a huge chunk of time and are represented by hundreds of genera [plural of genus]," Peterman says, and many reconstructions and dioramas show orthocones as horizontal swimmers like squid. "They were major components of marine ecosystems, yet we know very little about their swimming capabilities."
So he and Ritterbush took 3-D scans of fossils of Baculites compressus, an orthocone species that lived during the Cretaceous, and designed four different digital models, each with different physical properties. Find an orthocone digital model here.
How did they know how to weight the structures of the models? "Math," Peterman says. They adjusted the centers of mass and counterweights within the models, representing the balances of soft tissue and air-filled voids that the orthocone would likely have maintained in its life. "The resultant model is balanced the same as the living animal, allowing very detailed analyses of their movement," he says.
The resultant 3-D printed models were nearly two feet long. With the help of Emma Janusz and Mark Weiss at the U's George S. Eccles Student Life Center, the researchers set up a camera rig in a 7-foot-deep part of the Crimson Lagoon pool and released the models underwater to see how they naturally moved.
The results showed clearly that the most efficient method of movement was vertical, since moving side to side created a lot of drag. "I was surprised by how stable they are," Peterman says. "Any amount of rotation away from their vertical orientation is met with a strong restoring moment so many species of living orthocones were likely unable to modify their own orientations. Furthermore, the source of jet thrust is situated so low that, during lateral movement, much energy would be lost due to rocking."
The results also showed that orthocones may have been capable of high velocities among shelled cephalopods. That could have come in handy in evading predators. Looking at the results of the pool experiments and calculating the time needed to escape modern predators (as stand-ins for the orthocones' long-extinct predators), they found that orthocones may have been able to jet upward fast enough to evade animals similar to crocodiles or whales. They may not have been as lucky against fast swimmers like sharks, however.
So most species of orthocones couldn't have lived a horizonal-swimming lifestyle. "Instead," Peterman says, "species without counterweights in their shells assumed a vertical life habit, either feeding near the seafloor or vertically migrating in the water column. While orthocones were not as athletic or active as modern squid, they could have maintained the ability to thwart predators with upward dodges."
CAPTION
David Peterman in the AMMLab (Ammonoid Motility Modeling Laboratory) holding a 3-D-printed reconstruction of the planispiral ammonite, Paracoroniceras lyra.
CREDIT
David Peterman
Peterman and Ritterbush, along with recent graduate Nicholas Hebdon and Ryan Shell from the Cincinnati Museum Center, also ran a similar set of experiments with torticones, smaller cephalopods with a corkscrew-shaped shell. The results will be published in the American Association of Petroleum Geologists and Wyoming Geological Association Special Volume - Insights into the Cretaceous: Building on the Legacy of William A. Cobban (1916-2015). Although the torticones also likely preferred vertical movement, their shape caused a different result in the water, Peterman says."While orthocones were masters of vertical movement, torticones were masters of rotation."
Many mollusks today have similar helical shells, and some researchers previously assumed that torticones may have had a similar lifestyle, crawling along the seafloor. "However," Peterman says, "the hydrostatic models demonstrate that the chambered shells of torticone ammonoids had the capacity for neutral buoyancy, which would have liberated them from the seafloor. These ammonoids experience different forms of movement only possible in a free-swimming lifestyle."
In experiments conducted in a 50-gallon water tank (no swimming pool needed for the 6-inch-long torticone models that are available digitally here) the team found that the torticones naturally and efficiently rotated in the water just due to the shape of the shell, gently spinning face-first when descending and spinning the opposite direction when ascending. Also, they found, the placement of the torticones' source of thrust relative to their center of mass would have improved the efficiency of active rotation.
Rotating while descending, Peterman says, may have helped the torticones feed, allowing them to graze on small planktonic organisms.
"I was surprised at how easily torticones could rotate," Peterman says. "Even small thrusts such as breathing [gill ventilation] could have produced rotation of 20 degrees per second."
Both orthocones and torticones, because of their repeated appearance throughout the fossil record, not only show that cephalopods found some advantage to a straight or helical shell, as opposed to their nautilus-shaped coiled shell, but that an uncoiled shell might have evolved in times of "ecological saturation," when the ecological niches of coiled cephalopods were full.
Peterman says this work calls for a revision of how we envision the ancient ocean.
"These experiments," he says, "transform our understanding of ancient ecosystems. Rather than crawling along the seafloor like snails, or swiftly swimming like modern squid, these animals were assuming rather unique lifestyles. These experiments refine our understanding of these animals by painting a picture of ancient seascapes dotted with pirouetting helical cephalopods and vertically-oriented orthocones."
CAPTION
Motion tracking analysis of a 3D-printed torticone model.
The Wyoming Geological Association Special Volume study on torticones is forthcoming.
Complexity yields simplicity: The shifting dynamics of temperate marine ecosystems
Researchers from the University of Tsukuba find that ocean warming and acidification are shifting temperate coastal reefs to simple turf-dominated ecosystems
IMAGE: RESEARCHERS FROM THE UNIVERSITY OF TSUKUBA FIND THAT THE COMBINED EFFECTS OF OCEAN WARMING AND ACIDIFICATION IN TEMPERATE MARINE ECOSYSTEMS ARE RESULTING IN A LOSS OF KELP HABITAT AND A... view more
CREDIT: UNIVERSITY OF TSUKUBA
Shizuoka, Japan - At Shikine Island, Japan, kelp forests and abalone fisheries were once common, but over the last twenty years they have disappeared. Now, researchers from Japan have discovered that these temperate coastal marine ecosystems are becoming more "simple", losing biodiversity, complexity and their aesthetic values.
In a study published this month, researchers from the University of Tsukuba and international collaborators explored how the combined effects of ocean warming and acidification are changing temperate coastal marine ecosystems.
Tropical coastal seas are synonymous with coral reefs. As ocean temperatures cool toward the poles, corals give way to kelp as the main habitat-forming species. The shift from coral to kelp can clearly be seen along the 2000 km coastline of Japan, and changes to these ecosystems are already underway.
"Kelp forests are being lost globally as a result of warmer sea surface temperatures and heatwaves," says lead author, Dr Sylvain Agostini. "In Japan, this "isoyake", or "burnt seashore", is widespread. As ocean temperatures continue to increase, warm water corals are shifting northward into temperate reefs and could replace cold-water species."
There are three possible scenarios as coastal species shift. Temperate reefs could become more tropicalized and dominated by warm water corals, fishes, and other species. Alternatively, reefs may become dominated by tropical seaweeds or turf algae.
But another effect of increasing greenhouse gas emissions--ocean acidification--complicates matters. Acidification reduces the amount of carbonate in the ocean, which is needed by reef-building corals to create their structure. Decreases in carbonate ion concentrations could limit the colonization of new areas by fast-growing coral species.
To examine possible changes along the coast of Japan, the team used three locations at a similar latitude that represent three different scenarios (present, ocean warming, and ocean warming plus acidification). They examined the existing communities, and then transplanted kelp and coral species and measured their growth and survival at the different sites.
The team found that with both ocean warming and acidification, coastal ecosystems are likely to lose kelp forests but may not gain reef-building corals. The result is a simplified turf-dominated habitat.
"Warmer waters facilitate the growth and colonization of reef-building corals," explains Dr Ben Harvey. "But ocean acidification appears to negate these benefits. And kelp transplants did not survive in warmer waters, largely because they were eaten by warm water fishes."
The article, "Simplification, not 'tropicalization', of temperate marine ecosystems under ocean warming and acidification," was published in Global Change Biology at DOI: 10.1111/gcb.15455.
Study examines the role of deep-sea microbial predators at hydrothermal vents
Researchers emphasize the need for baseline information of microbial food webs
IMAGE: A VIEW OF THE APOLLO VENT FIELD AT THE NORTHERN GORDA RIDGE, WHERE SAMPLES WERE COLLECTED BY THE ROV HERCULES FOR STUDYING MICROBIAL PREDATORS view more
CREDIT: IMAGE CREDIT: OET/NAUTILUS LIVE
The hydrothermal vent fluids from the Gorda Ridge spreading center in the northeast Pacific Ocean create a biological hub of activity in the deep sea. There, in the dark ocean, a unique food web thrives not on photosynthesis but rather on chemical energy from the venting fluids. Among the creatures having a field day feasting at the Gorda Ridge vents is a diverse assortment of microbial eukaryotes, or protists, that graze on chemosynthetic bacteria and archaea.
This protistan grazing, which is a key mechanism for carbon transport and recycling in microbial food webs, exerts a higher predation pressure at hydrothermal vent sites than in the surrounding deep-sea environment, a new paper finds.
"Our findings provide a first estimate of protistan grazing pressure within hydrothermal vent food webs, highlighting the important role that diverse deep-sea protistan communities play in deep-sea carbon cycling," according to the paper, Protistan grazing impacts microbial communities and carbon cycling ad deep-sea hydrothermal vents published in the Proceedings of the National Academy of Sciences (PNAS).
Protists serve as a link between primary producers and higher trophic levels, and their grazing is a key mechanism for carbon transport and recycling in microbial food webs, the paper states.
The research found that protists consume 28-62% of the daily stock of bacteria and archaea biomass within discharging hydrothermal vent fluids from the Gorda Ridge, which is located about 200 kilometers off the coast of southern Oregon. In addition, researchers estimate that protistan grazing could account for consuming or transferring up to 22% or carbon that is fixed by the chemosynthetic population in the discharging vent fluids. Though the fate of all of that carbon is unclear, "protistan grazing will release a portion of the organic carbon into the microbial loop as a result of excretion, egestion, and sloppy feeding," and some of the carbon will be taken up by larger organisms that consume protistan cells, the paper states.
After collecting vent fluid samples from the Sea Cliff and Apollo hydrothermal vent fields in the Gorda Ridge, researchers conducted grazing experiments, which presented some technical challenges that needed to be overcome. For instance, "prepping a quality meal for these protists is very difficult," said lead author Sarah Hu, a postdoctoral investigator in the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution (WHOI).
"Being able to do this research at a deep-sea vent site was really exciting because the food web there is so fascinating, and it's powered by what's happening at this discharging vent fluid," said Hu, who was onboard the E/V Nautilus during the May-June 2019 cruise. "There is this whole microbial system and community that's operating there below the euphotic zone outside of the reach of sunlight. I was excited to expand what we know about the microbial communities at these vents."
Hu and co-author Julie Huber said that quantitative measurements are important to understand how food webs operate at pristine and undisturbed vent sites.
"The ocean provides us with a number of ecosystem services that many people are familiar with, such as seafood and carbon sinks. Yet, when we think about microbial ecosystem services, especially in the deep sea, we just don't have that much data about how those food webs work," said Huber, associate scientist in WHOI's Marine Chemistry and Geochemistry Department.
Obtaining baseline measurements "is increasingly important as these habitats are being looked at for deep-sea mining or carbon sequestration. How might that impact how much carbon is produced, exported, or recycled?" she said.
"We need to understand these habitats and the ecosystems they support," Huber said. "This research is connecting some new dots that we weren't able to connect before."
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The research was supported by NASA, the National Oceanic and Atmospheric Administration, Ocean Exploration Trust, the National Science Foundation, and WHOI.
About Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean's role in the changing global environment. WHOI's pioneering discoveries stem from an ideal combination of science and engineering--one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide--both above and below the waves--pushing the boundaries of knowledge and possibility. For more information, please visit http://www.whoi.edu
Authors :
Sarah K. Hu1*, Erica L. Herrera1, Amy R. Smith1, Maria G. Pachiadaki2, Virginia P. Edgcomb3, Sean P. Sylva1, Eric W. Chan4, Jeffrey S. Seewald1, Christopher R. German3, and Julie A. Huber1
Affiliations :
1 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
2 Department of Biology, Woods Hole Oceanographic Institution, Woods Hole MA, USA
3 Department of Geology & Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
4 School of Earth, Environment & Marine Sciences, UT-RGV, Edinburg, TX, USA
*corresponding author
Scientists get to the bottom of deep Pacific ventilation
The team's findings, with important implications for ocean biogeochemistry and climate science, have been published by Nature Communications in a paper by Associate Professor Mark Holzer from UNSW Science's School of Mathematics & Statistics, with co-authors Tim DeVries (UCSB) and Casimir de Lavergne (LOCEAN).
"The deep North Pacific is a vast reservoir of remineralized nutrients and respired carbon that have accumulated over centuries," says A/Prof. Holzer. "When these deep waters are returned to the surface, their nutrients support biological production and their dissolved CO2 can be released into the atmosphere. As such, the deep Pacific plays a key role in the earth's climate system."
But what are the pathways of the ocean circulation that supply newly ventilated surface water to the deep Pacific? And how and where does this old water eventually return to the surface? To date, there were two competing theories for the role that the overturning circulation plays in this.
One theory - the 'standard conveyor' - envisions broad overturning with Antarctic Bottom Water upwelling to around 1.5 km depth before flowing back south to the Southern Ocean. The other theory - the 'shadowed conveyor' - argues that the overturning is compressed to lie below about 2.5 km with a largely stagnant "shadow zone" above it.
"Our work reconciles these two theories: the shadowed conveyor correctly captures vertically compressed overturning beneath a shadow zone, while the standard view must be broadly interpreted in terms of water paths diffusing through the shadow zone. Because the shadow zone is largely shielded from the overturning circulation the question becomes how exactly does water get into and out of it," A/Prof. Holzer says.
Using novel mathematical analyses applied to a state-of-the-art ocean circulation model that optimally fits the circulation to observed tracer distributions and surface forcings, the authors were able to quantify in detail the pathways and timescales with which the shadow zone exchanges water with the surface ocean.
"Our analyses allowed us to come up with a new schematic of the large-scale deep circulation in the Pacific. We find that diffusive transport both along and across density surfaces plays a leading role in ventilating the shadow zone."
Contrary to the widely held view that Pacific deep waters exclusively follow density surfaces to upwell in the Southern Ocean, the authors found that only about half of the water in the shadow zone follows this route, with the other half returning to the surface in low latitudes and in the subarctic Pacific, helping to explain the high biological production there.
The scientists say this new understanding of the deep Pacific circulation and transport pathways will help interpret observed tracer distributions and biogeochemical processes.
"An exciting direction for future research is to understand how the shadow zone, already low in oxygen and sensitive to increased oxygen demand, shapes the response of the ocean's biological pump to climate change," A/Prof. Holzer says.
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Study shows that electronic air cleaning technology can generate unintended pollutants
IMAGE: ASSOCIATE PROFESSOR IN GEORGIA TECH'S SCHOOL OF CHEMICAL AND BIOMOLECULAR ENGINEERING AND THE SCHOOL OF EARTH AND ATMOSPHERIC SCIENCES view more
CREDIT: GEORGIA INSTITUTE OF TECHNOLOGY
As the Covid-19 pandemic raged, news reports show that sales of electronic air cleaners have surged due to concerns about airborne disease transmission. But a research team at the Georgia Institute of Technology has found that the benefits to indoor air quality of one type of purifying system can be offset by the generation of other pollutants that are harmful to health.
Led by Associate Professor Nga Lee "Sally" Ng in Georgia Tech's School of Chemical and Biomolecular Engineering and the School of Earth and Atmospheric Sciences, the team evaluated the effect of a hydroxyl radical generator in an office setting. Hydroxyl radicals react with odors and pollutants, decomposing them, and hydroxyl radical generators have been marketed to inactivate pathogens such as coronaviruses.
However, Ng's study found that in the process of cleaning the air, the hydroxyl radicals generated by the device reacted with volatile organic compounds present in the indoor space. This led to chemical reactions that quickly formed organic acids and secondary organic aerosols that can cause health problems. Secondary organic aerosols is a major component of PM2.5 (particulate matter with a diameter smaller than 2.5 ?m), and exposure to PM2.5 has been associated with cardiopulmonary diseases and millions of deaths per year.
The paper, "Formation of oxidized gases and secondary organic aerosol from a commercial oxidant-generating electronic air cleaner," is published in the journal Environmental Science and Technology Letters.
While the pandemic has made various types of electronic cleaners increasingly popular, Ng explained that consumers are probably not aware of the secondary chemistry taking place in the air, with the pollutants generated not being directly emitted by the cleaning device itself.
"There are increasing concerns regarding the use of electronic air cleaners as these devices can potentially generate unintended byproducts via oxidation chemistry similar to that in the atmosphere," Ng said.
Two types of air cleaning technologies are commonly used to remove indoor pollutants such as particles or volatile organic compounds and to inactivate pathogens: mechanical filtration and electronic air cleaners that generate ions, reactive species, or other chemical products such as photocatalytic oxidation, plasma, and oxidant-generating equipment (e.g., ozone, hydroxyl radical), among others.
Ng's team selected a hydroxyl generator for the study. They measured the oxygenated volatile organic compounds and the chemical composition of particles generated by the device in an office on the Georgia Tech campus.
While previous research reported pollutant formation from various electronic air cleaners (ionizers, plasma systems, photocatalytic systems with ultraviolet lamps, etc.), Ng believes that her team's study is the first to monitor the chemical composition of secondary pollutants in both gas and particle phases during the operation of an electronic device that dissipates oxidants in a real-world setting.
Advanced instrumentation made Ng's study possible. Gas-phase organic compounds were measured using a high-resolution time-of-flight chemical ionization mass spectrometer, purchased through a National Science Foundation major instrumentation grant. The study received support from Georgia Tech's Covid-19 Rapid Response fund.
Ng noted that future studies on air cleaning technology should not be limited to inactivation of viruses or reduction of volatile organic compounds, but should also evaluate potential oxidation chemistry and the formation of unintended harmful gaseous and particulate chemicals.
"More studies need to be conducted on the effects of these devices in a variety of environments," Ng said.
"Electronic air cleaners greatly rose in prominence because of the pandemic, and now there are a lot of these devices out there. Millions of dollars are being spent on these devices by businesses and schools. The market is huge.
"Our results show that care must be taken when choosing an adequate and appropriate air cleaning technology for a particular environment and task," she said.
Ng stressed the importance of future studies concerning the unintended effects of electronic purifiers, as these devices are not currently well regulated and do not have testing standards.
"There needs to be more peer-reviewed scientific data on electronic air cleaners," Ng said. "We hope that additional studies will lead to more government guidelines and regulation."
CAPTION
Air Quality Study: Aerosols
CREDIT
Sally Ng
CITATION: Joo et al., "Formation of oxidized gases and secondary organic aerosol from a commercial oxidant-generating electronic air cleaner." (Environmental Science & Technology Letters) https://pubs.acs.org/doi/10.1021/acs.estlett.1c00416
On the internet, nobody knows you're a dog -- or a fake Russian Twitter account
BUFFALO, N.Y. - Many legacy media outlets played an unwitting role in the growth of the four most successful fake Twitter accounts hosted by the Russian Internet Research Agency (IRA) that were created to spread disinformation during the 2016 U.S. presidential campaign, according to a study led by a University at Buffalo communication researcher.
In roughly two years beginning in late 2015, these accounts went from obscurity to microcelebrity status, growing from about 100 to more than 100,000 followers. With its heavily populated follower base ready to spread the word -- like all heavily engaged Twitter audiences -- the IRA could strategically deploy messages and provide visible metrics, creating an illusion of authority and authenticity that often escaped the scrutiny of casual consumers and professional journalists.
The frantic retweets, by what the study showed to be extreme ideological enclaves, certainly fueled the accumulation of followers, but Yini Zhang, PhD, an assistant professor of communication at UB, says that mainstream and hyperpartisan news media also significantly amplified IRA messaging and contributed to that follower growth by unknowingly embedding IRA tweets in their content.
Zhang says there was an ideological asymmetry to the study's results. Of the four puppet accounts in the study, @TEN_GOP and @Pamela_Moore13 posed as conservative trolls, while @Crystal1Johnson and @glod_up imitated liberals.
"We did not observe the same effect on the liberal and conservative accounts," she says. "The two conservative accounts received a huge boost from mainstream media and hyperconservative media quoting tweets in their news stories, but we did not see mainstream media and hyperprogressive media doing the same thing for the two liberal accounts."
The findings, published in the Journal of Communication, reveal how large social media followings can often depend on a combination of the dynamics within a particular platform and the news media's treatment of the messages emerging from those platforms. The evidence revealed in the study provides insights into the ecology of the 21st century political communication environment, suggesting that people's tendency to seek confirmation and engage with pro-attitudinal information, as well as the media's drive for audience attention, can work in favor of successful political disinformation actors.
In this case, constructive attempts to provide new information by integrating digital and legacy content ironically resulted in the unintended spread of disinformation, which Zhang defines as fabricated information that's intended to cause harm in ways that benefit its agents.
"Examining how and why these accounts grew so quickly and to such astounding proportions allows us to understand the mechanisms of influence accrual in the digital era," says Zhang, the study's corresponding author and an expert in social media and political communication. "None of this was intentional. It's about operational realties.
"But with this knowledge, we can begin to address and curtail the problem of disinformation."
The research team started their work with 2,700 puppet accounts released in 2017 by the House Intelligence Committee, which received the information from Twitter. From that group, the researchers identified the four most retweeted English-speaking accounts: two conservative accounts and two liberal accounts. They collected data from Twitter about the tweets and retweets of the IRA accounts. They then searched more than 200 media outlets across the ideological spectrum to determine where the uptake of IRA tweets was occurring.
"Strong social media posts can validate content," says Zhang. "But in their effort to turn heads, these legacy outlets were contributing to the growth of Russian sock puppet accounts."
The processes of incorporating digital content into mainstream media makes sense, but requires careful consideration, according to Zhang.
"Social media content looks very attractive given the cost cutting realities in mainstream media and lost advertising revenue," says Zhang. "But it also demonstrates a vulnerability within the current media economy.
"Turning heads might also mean unintentionally contributing to the growth of fake accounts, which should be subject to the same questions of credibility as any other news source: Is this account in fact what it actually claims to be?"
How a butterfly tree becomes a web
SMBE JOURNALS (MOLECULAR BIOLOGY AND EVOLUTION AND GENOME BIOLOGY AND EVOLUTION)
IMAGE: GENE FLOW BETWEEN SPECIES IS INDICATED WITH DOTTED BLUE LINES. BELOW: BUTTERFLIES OF TWO DIFFERENT SPECIES (HELICONIUS CYDNO CHIONEUS AND H. MELPOMENE ROSINA) MATING ON A PSYCHOTRIA POEPPIGIANA FLOWER IN... view more
CREDIT: IMAGE BY KRZYSZTOF KOZAK AND JORGE ALEMAN. PHOTO CREDITS: LUCA LIVRAGHI, MICHEL CAST.
Evolution is often portrayed as a tree, with new species branching off from existing lineages, never again to meet. The truth however is often much messier. In the case of adaptive radiation, in which species diversify rapidly to fill different ecological niches, it can be difficult to resolve relationships, and the phylogeny (i.e. evolutionary tree) may look more like a bush than a tree. This is because lineages may continue to interbreed as new species are established, and/or they may diverge and then re-hybridize, resulting in genetically mixed populations (known as admixture). Even after species diverge, the introduction of genes from one species to another (known as introgression) can occur. All of this results in a network of related species, rather than a simple tree. The extent to which these processes occur and their evolutionary and genomic impacts are not well understood, partially due to the "tree-like" assumptions of the models that are used to construct phylogenies. In a new study in Genome Biology and Evolution titled "Rampant genome-wide admixture across the Heliconius radiation," Krzysztof Kozak of the University of Cambridge and colleagues demonstrate the key role that interspecific gene flow played in the continent-wide adaptive radiation of the Heliconius butterflies. This study adds to the rich literature on Heliconius, a genus that provided some of the earliest evidence for the theory of evolution thanks to their distinctive wing patterns and colors, which help warn predators of their toxic nature.
According to Kozak and his co-authors, "the Neotropical Heliconius butterflies present an excellent opportunity to study the incidence and importance of gene flow in a recent adaptive radiation, due to the natural propensity of Heliconius and the sister genus Eueides to produce hybrids in the wild." In addition, the genes controlling their wing patterns are likely to be prime targets for selection and introgression, allowing different poisonous species to mimic each other and thus reinforcing the warning signal to predators.
The study included genomic data from 145 individuals, representing 40 of the 47 recognized Heliconius species and 6 of the 12 Eueides species, allowing a comprehensive investigation into departures from a strict tree model. The analysis revealed several discrepancies in the evolutionary history of individual genes, suggesting the possibility of extensive gene flow among lineages. Overall, the authors uncovered 13 instances of interspecific gene flow across the phylogeny, revealing a pattern of gene sharing that includes all of the major clades of Heliconius. "We found that gene flow between species, previously documented in a few closely related species, has been common across the group for millions of years," notes Dr. Kozak, "including both existing and ancestral lineages."
Intriguingly, when analyzing genes known to be involved in wing pattern and color, the authors found evidence for complex patterns of gene flow across several lineages, supporting previous reports and also identifying new cases of introgression. According to Dr. Kozak, "this provides further strong evidence that hybridization has been an important mechanism in the evolution of wing patterns, with sharing of relevant genes among many lineages allowing Heliconius to warn off avian predators." This makes Heliconius one of only a few known examples of a lineage that has experienced adaptive introgression of multiple genes across several different species.
In the future, Dr. Kozak and colleagues plan to use what they have learned about Heliconius to model their phylogenies as networks, rather than trees, allowing them to better understand the evolution of other butterfly traits, "from spatial learning to diverse arrays of pheromones and defensive toxins." In addition, they hope to relate their results to the geographic distribution of Heliconius: "We need to explore geographic variation and study both the incidence of hybridization (individuals of different species mating) and the levels of gene flow (genomic signature of mixing) between various populations, which so far has been done only for a few species." This type of work is likely to pose a considerable challenge, however, as many species and populations of Heliconius are rare and found only in remote locations, necessitating considerable field work.
As comprehensive genomic data sets continue to expand, Dr. Kozak hopes to investigate other organisms to see how widespread such interspecific gene flow may be. "As always in evolutionary biology, we need to ask how much our conclusions apply to other taxa. Very few butterflies, or insects indeed, have so far been studied in this depth: it remains to be seen how much evidence for genome-wide admixture we can find throughout the extreme diversity of insects."
