Friday, October 13, 2023

Study investigates impact of extreme weather events on ocean circulation in tropical Pacific

by Helmholtz Association of German Research Centres

How weather phenomena affect ocean circulation — *ASV change, sea surface temperature, and mixed layer depth. a Mixed layer depth (MLD)*

The strength of the wind has an important influence on ocean circulation. This is particularly true for extreme events such as storm fronts, tropical storms and cyclones. These weather patterns, which last from a few days to a few weeks, will change in the future due to climate change. In particular, the average energy input into the ocean from mid-latitude storms is expected to decrease, while equatorial regions will become more active. Scientists call these different weather patterns "Atmospheric Synoptic Variability" (ASV).

Two climate researchers—Dr. Olaf Duteil from the GEOMAR Helmholtz Center for Ocean Research Kiel and Professor Dr. Wonsun Park from the IBS Center for Climate Physics and Pusan National University, Korea—have now for the first time investigated the integrated effects of long-term changes in these weather patterns on the Pacific basin in a modeling study. The results show how important it is to take these changes into account in climate models. They have now published their findings in the journal npj Climate and Atmospheric Science.

From a climate point of view, the weather is usually considered as "noise" and is not systematically analyzed in long-term climate projections, say the two researchers. "However, it is not enough to look at average atmospheric properties, such as mean wind speeds, to understand the influence of climate change on the ocean," says Duteil, "it is crucial to consider the cumulative effect of short-term changes in weather patterns to get a complete picture."

The researchers expect that future changes in Atmospheric Synoptic Variability will affect the mixing of the ocean's layers, as a smaller or larger input of kinetic energy into the ocean due to weather phenomena will lead to less or more mixing, respectively. The researchers predict that the reduction in ASV in subtropical regions will lead to a shallowing of the mixing layer in the ocean, while it will become deeper at the equator as ASV increases

They also show that a future reduction in ASV decreases the strength of oceanic circulation systems—the so-called subtropical and tropical cells—and the large-scale ocean circulation. These systems connect mid-latitudes and equatorial latitudes via upper ocean pathways. They are driven by the trade winds north and south of the equator, regulate the upwelling of equatorial waters and play a fundamental role in determining the surface temperature of the oceans and thus primary productivity in the tropics.

This study highlights the need to better quantify ASV and weather patterns in climate models, as changes in ASV have a large impact on future upper ocean circulation and mean properties. Duteil states, "This quantification should be used to improve our confidence in projections of future climate, especially when analyzing large ensembles of climate models."

More information: Olaf Duteil et al, Future changes in atmospheric synoptic variability slow down ocean circulation and decrease primary productivity in the tropical Pacific Ocean, npj Climate and Atmospheric Science (2023).

DOI: 10.1038/s41612-023-00459-3

Journal information: npj Climate and Atmospheric Science

Provided by Helmholtz Association of German Research Centres Examining how weather patterns will change in the future

Research reveal large swings in past ocean oxygen

by Marcie Grabowski, University of Hawaii at Manoa

As the climate warms, there is major concern that Earth's ocean will lose oxygen. A study published in Geophysical Research Letters by oceanographers at the University of Hawai'i at Mānoa revealed that locked in ancient deep-sea sediments is evidence for oxygen loss in the world's ocean during past glacial periods, indicating that widespread oxygen loss with current climate change may not be permanent.

Scientists first measured oxygen in the oceans in the 1960s. Since then, they have observed decreasing levels in the mid-depths of the ocean—a phenomenon that can be explained in part by the fact that warmer waters hold less oxygen. Less oxygen in the water can lead to habitat loss for fish and other marine species that need oxygen to breathe. If the naturally-occurring low-oxygen regions in the Eastern Pacific expand in a warmer climate, Pacific Island fisheries could be significantly impacted.

Cobalt holds the clues in deep-sea sediments

"Ultimately, it would be helpful if we knew how low-oxygen regions of the ocean changed with past climate changes," said Nick Hawco, lead author of the study and assistant professor of oceanography, in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST).

"However, the problem is that oxygen is a gas, so we don't have any reservoirs of past oceans to test the oxygen content. Our new study builds off of prior work where we discovered that low oxygen water bodies in the Pacific are enriched in the metal cobalt."

"One of the biggest sources of cobalt to the oceans is where oxygen deficient zones intersect with the continental shelf, leach cobalt from the shelf, and then transport it across the ocean in a plume of low oxygen water," said Rhea Foreman, study co-author and oceanography researcher in SOEST. "The cobalt is subsequently incorporated into minerals that are deposited onto the seafloor and preserved in the sedimentary record."

Large swings in past ocean oxygen revealed — Deep sea sediments revealed ocean conditions from the past 145,000 years. Credit: Rhea Foreman/ UHM—SOEST

The researchers analyzed seafloor sediments from the past 145,000 years, a timeframe that includes the last major ice age. They found more cobalt in sediments from the past ice ages, compared to more recent sediments.

"This means that there was a build up of cobalt in the Pacific during the last ice age," said Hawco. "Because high cobalt is a proxy, or a stand-in, for low oxygen, this indicates there were probably larger regions of low oxygen waters in the Pacific during that time."

Time to adapt

One suggested explanation for low-oxygen waters being more common in cold climates is the change in ocean circulation that accompanies climate change. Today, complex currents flowing from west to east help add oxygen to the mid-depth waters of the tropical Pacific.

"If these currents weaken, the oxygen in the Pacific would decline," said Hawco. "This is what we think happened during the last glacial period. But we don't know how strongly—or how fast—these currents will respond to ocean warming."

This could mean that fish and other species are able to adapt to changing oxygen as long as these changes are slow enough, as appears to have happened in the past.

"We need to reduce emissions as soon as possible to buy time for these ecosystems to adapt to the climate change we are already locked into based on the last 150 years of carbon emissions," added Hawco.

More information: Nicholas J. Hawco et al, Expansion of Ocean Anoxia During Glacial Periods Recorded in the Cobalt Flux to Pelagic Sediments, Geophysical Research Letters (2023). DOI: 10.1029/2023GL105135

Journal information: Geophysical Research Letters

Provided by University of Hawaii at Manoa There may be good news about the oceans in a globally warmed world

THE ORIGINAL PALEO DIET

Neanderthal cuisine: Excavations reveal Neanderthals were as intelligent as Homo sapiens

by University of Trento

New insights on Neanderthal cuisine. Plos One has just published a study that sums up twenty years of archaeological excavations with a striking conclusion: Neanderthals were as intelligent as Homo sapiens — Neanderthal reconnstruction made by brother Kennis for Neanderthal Museum.

The fact that Neanderthals were able to make a fire and use it, among other things, for cooking, demonstrates their intelligence. "This confirms our observations and theories from previous studies," explains Diego Angelucci, archaeologist at the University of Trento and co-author of the study.

"Neanderthals were capable of symbolic thought, could create artistic objects, knew how to decorate their bodies using personal ornaments and had an extremely varied diet. Add to that that, based on our findings, we can say with certainty that they habitually ate cooked food. This ability confirms that they were as skilled as the Homo sapiens who lived millennia later."

But how did we learn that Neanderthals knew how to use fire? "There is a general agreement among archaeologists that they knew how to use fire. However, one thing is to use fire started by natural processes, such as lightning, another is to make it, feed it with wood and use it for cooking, heating and defense. In this study we demonstrate that there is no doubt that Neanderthals could make a fire and that fire was a central element in their daily life."

The article "Formation processes, fire use, and patterns of human occupation across the Middle Paleolithic of Gruta da Oliveira" was published October 11 in PLOS ONE.

Twenty years of excavations

The article documents and compares the remains of structured fires found in the same location: The Gruta de Oliveira in central Portugal, one of the most important European archaeological sites for the Middle Paleolithic. What is so exceptional about this cave is that excavations were conducted systematically and with great accuracy for more than 20 years between 1989 and 2012.

The works were led by an international group of archaeologists supervised by João Zilhão (University of Lisbon), who authored the study together with Diego Angelucci (UniTrento) and Mariana Nabais (IPHES, Catalan Institute for Human Paleoecology and Social Evolution, Tarragona).

The cave is part of the Almonda karst system, a vast network of caves placed at different elevations above a large spring that have been inhabited in different periods during Prehistory. The oldest layers of the Gruta de Oliveira, which includes a number of passages, date back to about 120,000 years ago, the most recent to about 40,000: It is believed that Neanderthals inhabited this place between 100,000 and 70,000 years ago.

"For us, Almonda is a gift that keeps on giving for the variety and quantity of artifacts and remains that we have found over the years: from the remains dating back to the Lower Paleolithic to the chipped stones of the Mousterian culture, there is really everything," Angelucci comments.

Hearths and food remains

In this case however, what caught the attention of archaeologists were the traces of hearths intentionally built and used in the cave. The archaeologists found about a dozen hearths at various stratigraphic levels in an excavation area of about 30 square meters and six meters deep. The unmistakable basin-like, circular structures were filled with remains.

Findings from inside and near the hearths demonstrate that the inhabitants of the caves used to cook their food. "We found burnt bones, burnt wood and ash remains. And the rock underneath—continues Angelucci—has been reddened by the heat: This is a crucial detail because it tells us that the structure is in a primary position. And it has always been there. Fire is a fundamental element in their daily lives. It makes the place comfortable and helps socialization. It gives back that basic idea of 'home' that perhaps could also apply to them."

A varied diet

What did Neanderthals eat? "We were able to find out what they ate and even the cooking techniques they used. We found the remains and burnt bones of cooked goats, deer, horses, aurochs (extinct bulls), rhinos, turtles, which were probably laid on their carapace and stewed on hot stones."

"Meat was on the menu in this inland cave, but in other excavations in caves overlooking the western Mediterranean Sea near Cartagena (Spain), remains of fish, mussels and mollusks, even roasted pine nuts, were found. We had already demonstrated in 2020 in another paper that appeared in Science that Neanderthals had a varied diet, but the Portuguese excavations have further confirmed that they used fire to cook food."

Despite the excavations, the archaeologists were not able to determine how the Neanderthals started a fire.

"Perhaps they did as in Neolithic times, striking flint rocks against another rock to throw sparks on a tinder, such as a dry nest for example. This is a prehistoric technique that was discovered by studying Ötzi, the Ice man. So far however, we have found no evidence of this."

Excavating a series of layers that cover 30,000 years, however, gave archaeologists the opportunity to compare the data with other sites in the same area that date back to Upper Paleolithic and involve a more recent period, where Homo sapiens were confirmed in the area. "We found no difference: they lived in the caves in similar ways. Their skills are also a sign of intelligence. They did not belong to different species, I would say that they were different human forms."

The study

This article represents the end of a long data analysis work that examined 30 years of findings. The Portuguese team of João Zilhão studied the stone tools, while Mariana Nabais analyzed the bone remains and conducted spatial analyses to examine the position of the finds in the cave and the location of the fires.

The research group of the University of Trento (Department of Humanities) focused on stratigraphy and microscopic studies. "We relied on the techniques of interdisciplinary archaeology: preliminary on site studies, meticulous excavation, accurate positioning of all the finds, systematic sieving, the precise method of collecting data in the field, the collection of samples for subsequent analysis under the microscope or in the laboratory: this type of archaeology is carried out with the most advanced methodologies. They require time and resources and this is what we teach our students."

More information: Diego E. Angelucci et al, Formation processes, fire use, and patterns of human occupation across the Middle Palaeolithic (MIS 5a-5b) of Gruta da Oliveira (Almonda karst system, Torres Novas, Portugal), PLOS ONE (2023). DOI: 10.1371/journal.pone.0292075

Journal information: Science , PLoS ONE

Provided by University of Trento Proof that Neanderthals ate crabs is another 'nail in the coffin' for primitive cave dweller stereotypes

Reexamination of ancient jawbone found in Ethiopia concludes it came from Homo erectus infant

by Bob Yirka , Phys.org

Reexamination of ancient jawbone found in Ethiopian highlands concludes it came from Homo erectus infant — The GAR IVE mandible. Credit: *Science* (2023). DOI: 10.1126/science.add9115

An international team of geoscientists, archaeologists and anthropologists has found evidence that strongly suggests an infant jawbone found in the Ethiopian highlands came from a Homo erectus child. In their study, reported in the journal Science, the group conducted multiple tests to learn the true nature of the fossil.

The jawbone was first uncovered back in 1981 at the Garba IV dig site in the Ethiopian highlands by a different team of researchers—it was subsequently nicknamed Little Garba. Over the years, several groups have tested the fossil to learn the species of the individual. No clear consensus was established, but it was found to be a member of the genus Homo.

To pinpoint the species, the researchers on this new effort applied synchrotron imaging to the teeth and compared those images with those of other hominin species. This showed the closest match to be Homo erectus.

Prior research had shown that the layers of sediment in which the jawbone was found were approximately 2 million years old, suggesting that Little Garba lived approximately 2 million years ago, making the jawbone one of the oldest known Homo erectus fossils ever found.

The research team then turned their attention to the stone tools found at the same level at the dig site. They found what they describe as a transition from Oldowan tools to Acheulean tools, which were more advanced. Prior research had shown that such tools were developed approximately 2 million years ago, coinciding with the age of Little Garba.

The researchers conclude that the evidence found at the Garba IV site suggests that once Homo erectus populations arrived in the highlands, they had to adapt to both the thinner air (Garba IV sits at 2,000 meters above sea level) and geographical conditions. That included improving their tools and weapons, which would allow them not only to take down prey found in the area, but to process it for use as food and materials for keeping warm in the cooler highlands.

More information: Margherita Mussi et al, Early Homo erectus lived at high altitudes and produced both Oldowan and Acheulean tools, Science (2023). DOI: 10.1126/science.add9115

Journal information: Science

Canadian cannabis legalization linked to increased and decreased hospitalization, depending on the province

by Justin Jackson , Medical Xpress

Research led by the Bruyère Research Institute, Canada, has looked into cannabis-related hospitalization rates before and after cannabis legalization in Canada.

In a paper, "Changes in Cannabis-Attributable Hospitalizations Following Nonmedical Cannabis Legalization in Canada," published in JAMA Network Open, the team finds links between rapid commercialization and the COVID-19 pandemic.

The study found 105,203 hospitalizations due to cannabis in Canada's four most populous provinces of Ontario, Quebec, Alberta, and British Columbia, covering the period from January 2015 to March 2021. The most significant relative increase in hospitalizations was for cannabis-induced psychosis.

Legalization with restrictions was associated with a gradual decrease in hospitalizations due to cannabis. The later rise of stores, cannabis products and the COVID-19 pandemic were associated with a sharp increase in cannabis-related hospitalization, with the exception of British Columbia, where rates dropped.

British Columbia, which comprised 25% of study participants, experienced a 10% reduction in hospitalization events after complete legalization and commercialization compared to pre-legalization rates.

Quebec, on the other hand, at 44% of study participants, was the slowest to allow commercialization and maintained stricter limitations on the types of products that could be sold, yet showed a 37% increase in hospitalization after complete legalization and commercialization compared to pre-legalization rates. Alberta showed an 18% increase, and Ontario was at 20%.

The findings suggest that the initial period following legalization in Canada, with tightly controlled products and limited store access, was not associated with increased hospitalizations due to cannabis. Hospitalizations increased sharply following widespread commercialization in some provinces and decreased in other areas.

Associations were seen between expanded access and increased cannabis hospitalizations, particularly for cannabis-induced psychosis. The unfortunate overlap of store and product expansion and the COVID-19 pandemic challenge the explicit attribution of increases to cannabis access alone.

Canada legalized the sale of cannabis in October 2018, with each province and territory creating its own regulations regarding how cannabis would be sold and the types of products that could be allowed. Initially, all provinces in Canada were only allowed to sell dried cannabis.

In October 2019, cannabis producers were allowed to apply to begin selling new high-potency cannabis products, including edibles, vape pens, and concentrates. Most provinces, other than Quebec, allowed these products to come to market starting in early 2020.

Provinces also took differing approaches to cannabis retail store access. Alberta had a rapid expansion of stores and legal sales immediately following legalization. In contrast, Ontario and British Columbia initially had very low cannabis sales and store access, followed by rapid growth beginning in early 2020. Quebec had the lowest per capita stores and sales throughout the study despite having the highest hospitalization increase from start to finish.

The different approaches to legalization allowed the researchers an opportunity to explore how different regulatory approaches to cannabis markets impact the overall burden on public health. Unfortunately, a study related to hospitalization rates that has a pandemic walk through the middle of the critical data collection period has an unavoidable confounding bias.

COVID-19 pandemic aside, other limitations exist in finding associations between legalization stages and hospital visits. One is that the three-year pre-legalization period (2015–2018) already showed a significantly increased trend in cannabis-related hospitalization rates. That trend, provided in the study, appears to have been slowed by legalization.

Another factor is that patients may simply be more likely to seek medical help and disclose cannabis use after legalization when there is less stigma and no fear of criminal prosecution.

More information: Daniel T. Myran et al, Changes in Cannabis-Attributable Hospitalizations Following Nonmedical Cannabis Legalization in Canada, JAMA Network Open (2023). DOI: 10.1001/jamanetworkopen.2023.36113

Journal information: JAMA Network Open

Pediatric cannabis poisoning increased with edible cannabis sales

CRISPR CRITTERS

Thousands of programmable DNA-cutters found in algae, snails, and other organisms

by Jennifer Michalowski, Massachusetts Institute of Technology

A diverse set of species, from snails to algae to amoebas, make programmable DNA-cutting enzymes called Fanzors—and a new study from scientists at MIT's McGovern Institute for Brain Research has identified thousands of them. Fanzors are RNA-guided enzymes that can be programmed to cut DNA at specific sites, much like the bacterial enzymes that power the widely used gene-editing system known as CRISPR. The newly recognized diversity of natural Fanzor enzymes, reported Sept. 27 in the journal Science Advances, gives scientists an extensive set of programmable enzymes that might be adapted into new tools for research or medicine.

"RNA-guided biology is what lets you make programmable tools that are really easy to use. So the more we can find, the better," says McGovern Fellow Omar Abudayyeh, who led the research with McGovern Fellow Jonathan Gootenberg.

CRISPR, an ancient bacterial defense system, has made it clear how useful RNA-guided enzymes can be when they are adapted for use in the lab. CRISPR-based genome editing tools developed by MIT professor and McGovern investigator Feng Zhang, Abudayyeh, Gootenberg, and others have changed the way scientists modify DNA, accelerating research and enabling the development of many experimental gene therapies.

Researchers have since uncovered other RNA-guide enzymes throughout the bacterial world, many with features that make them valuable in the lab. The discovery of Fanzors, whose ability to cut DNA in an RNA-guided manner was reported by Zhang's group earlier this year, opens a new frontier of RNA-guided biology. Fanzors were the first such enzymes to be found in eukaryotic organisms—a wide group of lifeforms, including plants, animals, and fungi, defined by the membrane-bound nucleus that holds each cell's genetic material. (Bacteria, which lack nuclei, belong to a group known as prokaryotes.)

"People have been searching for interesting tools in prokaryotic systems for a long time, and I think that that has been incredibly fruitful," says Gootenberg. "Eukaryotic systems are really just a whole new kind of playground to work in."

One hope, Abudayyeh and Gootenberg say, is that enzymes that naturally evolved in eukaryotic organisms might be better suited to function safely and efficiently in the cells of other eukaryotic organisms, including humans. Zhang's group has shown that Fanzor enzymes can be engineered to precisely cut specific DNA sequences in human cells. In the new work, Abudayyeh and Gootenberg discovered that some Fanzors can target DNA sequences in human cells even without optimization. "The fact that they work quite efficiently in mammalian cells was really fantastic to see," Gootenberg says.

Prior to the current study, hundreds of Fanzors had been found among eukaryotic organisms. Through an extensive search of genetic databases led by lab member Justin Lim, Gootenberg and Abudayyeh's team has now expanded the known diversity of these enzymes by an order of magnitude.

Among the more than 3,600 Fanzors that the team found in eukaryotes and the viruses that infect them, the researchers were able to identify five different families of the enzymes. By comparing these enzymes' precise makeup, they found evidence of a long evolutionary history.

Fanzors likely evolved from RNA-guided DNA-cutting bacterial enzymes called TnpBs. In fact, it was Fanzors' genetic similarities to these bacterial enzymes that first caught the attention of both Zhang's group and Gootenberg and Abudayyeh's team.

The evolutionary connections that Gootenberg and Abudayyeh traced suggest that these bacterial predecessors of Fanzors probably entered eukaryotic cells, initiating their evolution, more than once. Some were likely transmitted by viruses, while others may have been introduced by symbiotic bacteria. The research also suggests that after they were taken up by eukaryotes, the enzymes evolved features suited to their new environment, such as a signal that allows them to enter a cell nucleus, where they have access to DNA.

Through genetic and biochemical experiments led by biological engineering graduate student Kaiyi Jiang, the team determined that Fanzors have evolved a DNA-cutting active site that is distinct from that of their bacterial predecessors. This seems to allow the enzyme to cut its target sequence more precisely the ancestors of TnpB, when targeted to a sequence of DNA in a test tube, become activated and cut other sequences in the tube; Fanzors lack this promiscuous activity. When they used an RNA guide to direct the enzymes to cut specific sites in the genome of human cells, they found that certain Fanzors were able to cut these target sequences with about 10 to 20 percent efficiency.

With further research, Abudayyeh and Gootenberg hope that a variety of sophisticated genome editing tools can be developed from Fanzors. "It's a new platform, and they have many capabilities," says Gootenberg.

"Opening up the whole eukaryotic world to these types of RNA-guided systems is going to give us a lot to work on," Abudayyeh adds.

More information: Kaiyi Jiang et al, Programmable RNA-guided DNA endonucleases are widespread in eukaryotes and their viruses, Science Advances (2023). DOI: 10.1126/sciadv.adk0171

Journal information: Science Advances

Provied by Massachusetts Institute of Technology

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.Researchers uncover new CRISPR-like system in animals that can edit the human genome

Research shows wildfire smoke may linger in homes long after initial blaze

by Colorado State University

CSU postdoctoral fellow Kathryn Mayer led an aerosol-measurement experiment that introduced wildfire smoke into the home. Credit: John Eisele/Colorado State University Photography

Newly published research on indoor air quality from Colorado State University shows wildfire smoke may linger in homes long after the initial blaze has been put out or winds have shifted.

The findings, published in Science Advances, show that wildfire smoke can attach to home surfaces like carpet, drapes or counters—extending the exposure for those inside and potentially causing health problems even after an initial cleaning activity by air purifiers. However, Professor Delphine Farmer said the research also shows that simple surface cleaning—like vacuuming, dusting or mopping—can reduce exposure and limit risk.

The research illustrates the hidden and persistent health threats many in the Western U.S. are facing given the increase in wildfires over the last decade, she said.

"This research shows that events like the Marshall Fire in Colorado, the wildfires in Canada and the recent fires in Hawaii present serious exposure potential—not just when they occur but well after," said Farmer, who is based in the Department of Chemistry at CSU. "This paper is a key initial step towards providing actionable and practical information on how to protect yourself and clean your home."

To better understand how smoke enters and then stays in buildings, researchers burned pine wood chips in a net zero energy residential testing facility operated by the National Institute of Standards and Technology (NIST) in Maryland. That facility is frequently used to study how different systems impact the ways energy, water and air move through a single-family house. The detailed instrumentation available for that work was perfectly suited to this research, said Dustin Poppendieck, an environmental researcher at NIST who helped coordinate the project.

The Net-Zero Energy Residential Test Facility (NZERTF) is a unique laboratory at the National Institute of Standards (NIST) in Gaithersburg, Md. Credit: John Eisele/Colorado State University Photography

Researchers at Colorado State University worked with the National Institute of Standards and Technology to test how wildfire smoke lingers on surfaces in homes like carpet despite initial cleaning activity. Their findings were published in Science Advances. Credit: John Eisele/Colorado State University Photography

"The NIST Net Zero House allowed the researchers to track the movement and transformation of chemicals in the air and onto surfaces in real time using instruments in ways that don't interfere with the behavior of the smoke," said Poppendieck.

Those smoke injection sessions occurred regularly over several days, and Farmer said the total amount applied was comparable or slightly under the particulate levels seen during the Canadian wildfires. The team then took careful measurements of air quality levels and surface conditions after opening exterior doors and windows, cleaning and use of the home's built-in air cleaning systems.

The CSU team was particularly interested in the gas-phase of compounds developing from the smoke, while other teams from the University of California San Diego, CU Boulder and the University of North Carolina Chapple Hill explored different phases and interactions across the home. The team then compared findings between states to confirm what was actually happening in the home after the burn.

Farmer said findings from this interdisciplinary research approach could also be applicable to other large air pollution events like the train derailment in East Palestine, Ohio, where the same principles of compounds sticking to surfaces are likely to occur.

Because there has not been a lot of similar indoor air research, the team leaned on previous findings from others around the effects of cigarette smoke to inform their approach. Farmer said burning nicotine causes specific compounds with well-known health concerns and that the comparison to their project findings was informative.

"Nicotine reacts on surfaces to create a particularly nasty set of compounds called nitrosamines, which is where the real concern from third-hand smoke that is left behind comes from," she said. "Whereas with wildfire smoke, we found there was a huge diversity of organic compounds that stick to surfaces, which then slowly bleed off."

The amount, persistence and variety of compounds from the wildfire smoke in each case could potentially change the recommended approaches for cleaning the indoor spaces. Farmer said that is an area of research the team hopes to explore in the future.

Researcher cleaning the house during testing. Credit: John Eisele/Colorado State University Photography

Delphine Farmer. Credit: John Eisele/Colorado State University Photography

For now, she said the team was able to show that the amount of smoke left on surfaces was proportional to the surface area that was cleaned. That means simple cleaning and specifically addressing large but little noticed spaces that may trap harmful compounds such as cabinets and HVAC systems could be beneficial right away.

"As we continue this research, we would like to know just how effective different cleaning approaches are and when residents should move from relatively simple steps like using commercial cleaning supplies for mopping to more drastic steps like replacing the drywall altogether," Farmer said.

Farmer's team was also recently funded to research how smog may enter and remain in the home in much the same way as wildfire smoke. That work will be particularly important in Colorado where ground-level ozone pollution is a continuing issue.

"In the future I want to explore how the economics of making a more energy efficient building play into these questions and help people understand the risks and potential solutions available to them," Farmer said. "CSU is well positioned to lead this kind of interdisciplinary work and address the practical implications because of the land-grant service mission that drives our university."

More information: Jienan Li et al, The persistence of smoke VOCs indoors: partitioning, surface cleaning, and air cleaning in a smoke-contaminated house, Science Advances (2023). DOI: 10.1126/sciadv.adh8263. www.science.org/doi/10.1126/sciadv.adh8263

Journal information: Science Advances

Provided by Colorado State University

Explore furtherIndoor air quality experiments show exposure risks while cooking, cleaning

What phytoplankton physiology has to do with global climate

by Helmholtz Association of German Research Centres

Phytoplankton, tiny photosynthetic organisms in the ocean, play a crucial role in the global carbon cycle and influence Earth's climate. A new study reveals how variations in the physiology of phytoplankton, particularly regarding nutrient uptake, can impact the chemical composition of the ocean and even the atmosphere. This suggests that changes in marine phytoplankton physiology can affect global climate.

Phytoplankton in the ocean are central to the global carbon cycle as they perform photosynthesis, capturing and transporting carbon (C) to the deep ocean. The growth of phytoplankton relies not only on carbon but also on nitrogen (N) and phosphorus (P), which are crucial for their cellular functioning.

Phytoplankton stoichiometry defines the relative proportions of different elements such as C, N, and P in these organisms. Key connections exist between phytoplankton stoichiometry and climate through interdependencies between the oceanic carbon pump, nutrient cycling, food web dynamics, and responses to climate-related factors like atmospheric carbon dioxide (CO2) concentration and temperature.

In the 1930s, the American oceanographer Alfred C. Redfield made an important discovery: he found that the concentrations of the elements C, N, and P in the marine phytoplankton roughly follow a fixed ratio of approximately 106:16:1—the ratio now named after him, the Redfield ratio.

Surprisingly, Redfield's research also revealed that in the seawater samples he collected, the concentration of nitrate, a primary nitrogen nutrient source, was, on average, 16 times higher than the concentration of phosphate, a primary phosphorus nutrient source. The nitrogen-to-phosphorus (N:P) ratios in both phytoplankton and seawater are remarkably similar, indicating a strong connection between the particulate (phytoplankton) and dissolved (seawater) nutrient pools.

The question of whether the N:P ratio of the dissolved pool controls the ratio in particulate material, or vice versa, has long puzzled the marine science community. "It's a chicken-and-egg question," says Dr. Chia-Te Chien, a researcher in the Biogeochemical Modeling Research Unit at the GEOMAR Helmholtz Center for Ocean Research in Kiel, who is investigating the role of variable stoichiometry of phytoplankton in the marine biogeochemistry.

Together with his colleagues, he has now carried out a modeling study that examines the relationship between the ratios of nitrogen and phosphorus in dissolved inorganic and particulate organic matter in seawater. The study, now published in the journal Science Advances, emphasizes the importance of variable C:N:P ratios of phytoplankton for regulating dissolved oceanic nutrient ratios on a global scale and highlights marine oxygen levels as a critical regulator in the Earth system.

To investigate these relationships, the authors used a computer model of algal physiology coupled to an Earth system model, wherein phytoplankton dynamically optimize their C:N:P ratios in response to varying environmental conditions. In the computer model, they could alter the characteristics of phytoplankton and observe how this changed the nitrogen and phosphorus ratios in the water.

They carried out an ensemble of 400 simulations, which differ in the minimal nitrogen and phosphorus contents required by algae to stay alive. The model results reveal intricate feedback mechanisms involving changes in the nitrogen and phosphorus content of phytoplankton, oceanic oxygen levels, N2 fixation by nitrogen-fixing phytoplankton, and denitrification.

These model results challenge the commonly hypothesized strong link between phytoplankton and seawater nutrient ratios. Rather than attempting to uncover the reasons behind the resemblance in the currently observed ratios between phytoplankton and seawater, the results highlight that these ratios are not inherently similar. In other words, the similarity, as it is observed these days, is a specific state, and this state may be subject to change, at least on a time scale that is not covered by the many decades of ocean in situ observations.

Additionally, the analysis highlights the potentially substantial influence of phytoplankton subsistence nitrogen and phosphorus quotas on atmospheric CO2 levels on geological time scales. Traditionally, stoichiometric variations of the phytoplankton and within the marine ecosystem were considered to have a relatively minor impact on marine biogeochemistry and, consequently, atmospheric CO2 levels. This view could now be questioned, because this study points to the potential importance of a physiological detail for climate conditions on our planet.

The authors explain the significance of the findings, "Our results demonstrate that the concentration of atmospheric CO2 as well as the ocean and air temperature are remarkably sensitive to variations in elemental stoichiometry induced by changes in phytoplankton physiology." Understanding these connections could help scientists make more accurate predictions about how our planet's ecosystems and climate will evolve in the future.

More information: Chia-Te Chien et al, Effects of phytoplankton physiology on global ocean biogeochemistry and climate, Science Advances (2023). DOI: 10.1126/sciadv.adg1725