New twists on tornadoes: Earth scientist studies why U.S. has so many tornadoes

PURDUE UNIVERSITY

 

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DAN CHAVAS IS AN EXPERT AT EXTREME WEATHER: BOTH THE CLIMATE SCIENCE THAT CREATES THE CONDITIONS AND THE PHYSICS OF THE WEATHER ITSELF, INCLUDING HURRICANES, SEVERE THUNDERSTORMS AND TORNADOES.

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CREDIT: (PURDUE UNIVERSITY PHOTO/GRETA BELL)

WEST LAFAYETTE, Ind. — Across the Midwest during the warmer months, studying the sky for signs of storms and tornadoes becomes one of the most popular pastimes.

Dan Chavas, an associate professor in the Department of Earth, Atmospheric, and Planetary Sciences at Purdue University’s College of Science, takes it further: All day every day, he studies what makes tornadoes tick. Working at the intersection of climate science and meteorology, he looks at the big picture of what causes severe storms and tornadoes — and what dictates where they occur.

“I study both the climate and extreme weather,” Chavas says. “My research asks, ‘Why do we have severe thunderstorms or tornadoes at all?’ There are specific regions on Earth that have more storms, more tornadoes than other places. What creates these stormy regions?”

The central and eastern regions of the United States are among the top spots for severe thunderstorms and form the hot spot for the Earth’s most damaging and frequent tornadoes. Chavas uses real-world computer models to conduct experiments to determine what contributes to the formation of these storms. 

“We have had these decades-old assumptions about what causes storms,” he says. “We’re validating those hypotheses and figuring out what makes North America such a hot spot.”

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ADDITIONAL INFORMATION

• Would we still have severe thunderstorms over North America if the Gulf of Mexico were filled in with land?
• Cold winters don't mean there’s no global warming
• Future hurricanes may cause havoc inland

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Moving heaven and earth

Chavas isn’t a storm chaser. He’s not out there in a weather van topped with satellite wires hunting down individual storms for the insights they might yield. Nor can he grow storms in his lab or unleash tornadoes to understand their anatomy or behavior.

Instead, he harnesses decades of rich, detailed historical data and complex computer models to imagine and test what-if scenarios. He’s a storm tester.

“We use weather and climate models, as well as extensive databases of thunderstorms, lightning strikes, atmospheric data and more, to ask, ‘What if the world was different?’” Chavas says. “We can use these models as laboratories to ask questions like ‘What happens to the weather if you flatten the Rocky Mountains? What about if you fill in the Gulf of Mexico? What aspects of the modern continental and mountain configurations really matter? Let’s actually test this prevailing, conventional wisdom.’” 

Both of those hypotheticals — flattening the Rockies and filling in the Gulf of Mexico — are the focus of studies Chavas and his team have conducted.

For more than 50 years, established wisdom said that the Gulf of Mexico, a source of warm, wet air flowing inland to the east of the Rocky Mountains, plays a major role in the formation of North America’s tornadoes. But no one knew for sure. 

“It was a very reasonable hypothesis,” Chavas says. “There were a lot of very reasonable explanations. But no one had been able to test these 50-year-old ideas because they came about when there weren’t climate models with the necessary computational power. Now we can really start to understand the physics of the situation.” 

When his team virtually filled in the Gulf of Mexico with land, they found that a dry Gulf of Mexico affected the frequency and severity of storms far less than they had expected. Without the Gulf of Mexico, severe thunderstorms shifted eastward from the central Great Plains into Illinois, although they were reduced over southern Texas. 

“Severe thunderstorms and tornadoes form in environments with specific ingredients for how temperature, moisture, and especially wind speed and direction change with height in the atmosphere,” Chavas says. “The climate determines where and when those ingredients can be found together to produce these types of storms. Computer models let us understand why the ingredients are there in the first place and what role they each play in the weather we see.” 

In his most recent study with graduate student Funing Li, just published in the Proceedings of the National Academy of Sciences, the team compared severe weather potential in North America, famous for tornadoes, with South America, which has a geography similar to North America’s and also many severe thunderstorms, but far fewer tornadoes. Their research has been funded by the National Science Foundation and NASA.

They found that the rough texture of the land surface east of the Andes mountains, its roughness determined in part by the hills and tall trees of the Amazon region, may play a large role in preventing tornadoes over central South America. In contrast, in North America many tornadoes form east of the Rockies, where air flows in from the much smoother ocean surface of the Gulf of Mexico. The team first used climate model experiments in which equatorial South America was smoothed to be similar to an ocean surface, which drastically increased central South America’s tornado potential. They also performed experiments in which the Gulf of Mexico region was roughened to be similar to a forested land surface, which strongly suppressed North American tornado potential. 

“A rough surface upstream means that downstream the wind is no longer changing speed and direction with height very strongly near the surface, which we refer to as ‘wind shear,’” Chavas says. “It doesn’t change ingredients for severe thunderstorms, but the wind shear in the 1 kilometer of air above the ground is a critical ingredient for tornadoes.” 

Storm warning

Real weather and real-world applications fascinate Chavas, a fascination born after a storm-torn tree fell on his house in Wisconsin when he was 4 years old.

The real-world implications of his research — what will the weather be like next week, next month, next year and next century — are what drives him.

“If we want to understand how climate change will affect weather in the future, we need to understand how climate determines weather in the first place,” Chavas says. “We don’t have a very good understanding of how climate controls the severe weather we have.”

Understanding how surface roughness and land use changes weather, for example, may enable future humans to better predict — and even partially affect — weather patterns. If the rough land of the Amazon, including a component from the trees of the Amazon, protects South America from tornadoes, could the regrowth of the United States’ eastern forests affect tornadoes, too?

Climate change affects the flow patterns of the atmosphere and moisture distribution on land, Chavas says.

“If we change the land surface and the trajectory of air flowing inland from the Gulf of Mexico, it may have a direct impact on these ingredients that give rise to tornadoes farther inland. When we think about climate change, we think about it getting hotter and the land getting drier. But if the jet stream changes where and how quickly air flows inland, it can change where and how tornadoes form. Places that didn’t see them before may see them more, and places that had more may see fewer,” he says. “We need to understand the weather now to help us better predict the weather of the future.”

About Purdue University

Purdue University is a public research institution demonstrating excellence at scale. Ranked among top 10 public universities and with two colleges in the top four in the United States, Purdue discovers and disseminates knowledge with a quality and at a scale second to none. More than 105,000 students study at Purdue across modalities and locations, including nearly 50,000 in person on the West Lafayette campus. Committed to affordability and accessibility, Purdue’s main campus has frozen tuition 13 years in a row. See how Purdue never stops in the persistent pursuit of the next giant leap — including its first comprehensive urban campus in Indianapolis, the Mitchell E. Daniels, Jr. School of Business, Purdue Computes and the One Health initiative — at https://www.purdue.edu/president/strategic-initiatives. 

Writer/Media contact: Brittany Steff, bsteff@purdue.edu

Source: Dan Chavas, dchavas@purdue.edu

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2315425121 

ARTICLE TITLE

Upstream surface roughness and terrain are strong drivers of contrast in tornado potential between North and South America

ARTICLE PUBLICATION DATE

18-Jun-2024

 

Archaeology: Occupational hazards for ancient Egyptian scribes

Peer-Reviewed Publication

SCIENTIFIC REPORTS

Repetitive tasks carried out by ancient Egyptian scribes — high status men with the ability to write who performed administrative tasks — and the positions they sat in while working may have led to degenerative skeletal changes, according to a study published in Scientific Reports.

Petra Brukner Havelková and colleagues examined the skeletal remains of 69 adult males — 30 of whom were scribes — who were buried in the necropolis at Abusir, Egypt between 2700 and 2180 BCE. They identified degenerative joint changes that were more common among scribes compared to men with other occupations. These were in the joints connecting the lower jaw to the skull, the right collarbone, the top of the right humerus (where it meets the shoulder), the first metacarpal bone in the right thumb, the bottom of the thigh (where it meets the knee), and throughout the spine, but particularly at the top. The authors also identified bone changes that could be indicative of physical stress caused by repeated use in the humerus and left hip bone, which were more common among scribes than men with other occupations. Other skeletal features that were more common among scribes were an indentation on both kneecaps and a flattened surface on a bone in the lower part of the right ankle.

The authors suggest that the degenerative changes observed in the spines and shoulders of scribes could result from them sitting for prolonged periods in a cross-legged position with the head bent forwards, the spine flexed, and their arms unsupported. However, changes to knees, hips, and ankles could indicate that scribes may have preferred to sit with the left leg in a kneeling or cross-legged position and the right leg bent with the knee pointing upwards (in a squatting or crouching position). The authors note that statues and wall decorations in tombs have depicted scribes sitting in both positions, in addition to standing, while working. Degeneration to the jaw joints could have resulted from scribes chewing the ends of rush stems to form brush-like heads they could write with, while degeneration to the right thumb could have been caused by repeatedly pinching their pens.

The findings provide greater insight into the lives of scribes in ancient Egypt during the third millennium BCE.

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Article details

Ancient Egyptian scribes and specific skeletal occupational risk markers (Abusir, Old Kingdom)

DOI: 10.1038/s41598-024-63549-z

Corresponding Author:

Petra Brukner Havelková
National Museum in Prague, Prague, Czech Republic
Charles University, Prague, Czech Republic
Email: petra.havelkova@nm.cz

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JOURNAL

Scientific Reports

DOI

10.1038/s41598-024-63549-z 

ARTICLE TITLE

Ancient Egyptian scribes and specific skeletal occupational risk markers (Abusir, Old Kingdom)

ARTICLE PUBLICATION DATE

27-Jun-2024

 

NIST researchers identify a cheaper, more convenient method to detect asbestos

The scientists found that scanning electron microscopy (SEM) can serve as a replacement for more labor-intensive, costly techniques used in construction.

Peer-Reviewed Publication

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST)

 

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IMAGES OF ASBESTOS FIBERS TAKEN BY SCANNING ELECTRON MICROSCOPY (SEM).

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CREDIT: J. HOLM/NIST

For decades, a laboratory procedure known as transmission electron microscopy (TEM) has been used to test for asbestos in samples taken at construction sites.

In 1989, the U.S. Environmental Protection Agency (EPA) required most schools undergoing asbestos abatement to use TEM to test for the presence of asbestos fibers in air samples before reopening. Several states require or recommend using TEM for testing as part of asbestos removal in commercial buildings.  

But TEM must be carried out in a specialized lab by highly trained staff and can be expensive. Another approach, phase contrast microscopy, is easier and cheaper but less precise.

Now, researchers at the National Institute of Standards and Technology (NIST) have determined that a third option, scanning electron microscopy (SEM), can achieve results roughly comparable to TEM. SEM is a “viable alternative to the current regulatory methods for asbestos identification and classification,” the NIST researchers Jason Holm and Elisabeth Mansfield wrote in a new paper published in Analytical Methods.

Since SEM is, in many cases, cheaper and more convenient than TEM, the finding could potentially speed up and reduce the expense of asbestos remediation in the United States, which costs an estimated $3 billion every year.

Asbestos is a naturally occurring mineral whose fibers were used for insulation, weather- and fire-proofing and reinforcing building materials. Its use began declining in the 1970s as researchers became aware of its health risks, including its link to cancer. In March, the EPA banned the last form of asbestos still in use.

As their names suggest, both TEM and SEM are types of electron microscopy. In both methods, technicians focus electron beams on a microscopic amount of material. Electrons interact with the material to produce highly detailed information on the material’s composition, structure and shape.

With TEM, the electrons pass through the sample, whereas with conventional SEM, they are reflected off the surface. This enables TEM to produce more detailed images and probe the surface’s interior. TEM also offers much better spatial resolution — the ability to distinguish between objects very close together — than SEM.

But in recent years, SEM manufacturers have improved the technology’s imaging power and other capabilities. Several companies now produce tabletop SEMs, making it possible to use the technology in the field, while TEM must still be done in a lab. Holm said training to use and operate SEM equipment can be completed in several months, while “expertise in TEM can take years to establish.”

“There are some capabilities TEM has which SEM doesn’t, but we think SEM is good enough” for use in asbestos abatement, said Holm.

To test SEM on asbestos, Holm and Mansfield used NIST Standard Reference Material (SRM) 1866, a sample of asbestos fibers the agency produces for labs to benchmark their equipment and testing procedures. The SRM comes with extensive data characterizing the properties of the material.

Using SEM, the researchers analyzed SRM 1866. Their results closely agreed with those listed in the SRM’s documentation, indicating the method’s accuracy.

Holm and Mansfield summarized SEM’s potential advantages by writing that it could result in “lower equipment cost, less stringent operator training requirements, increased sample throughput and greater field of view compared to TEM.”

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JOURNAL

Analytical Methods

DOI

10.1039/D4AY00555D 

ARTICLE TITLE

Transmission electron imaging and diffraction of asbestos fibers in a scanning electron microscope

ARTICLE PUBLICATION DATE

24-Jun-2024

 SPACE

Last segment of the world’s largest telescope mirror successfully cast

ESO

 

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THE PRIMARY MIRROR OF ESO’S EXTREMELY LARGE TELESCOPE (ELT), KNOWN AS M1, WILL BE BY FAR THE LARGEST MIRROR EVER MADE FOR A TELESCOPE. WITH A DIAMETER OF MORE THAN 39 METRES, M1 IS TOO LARGE TO BE MADE FROM A SINGLE PIECE OF GLASS AND WILL INSTEAD CONSIST OF 798 HEXAGONAL SEGMENTS, EACH ABOUT FIVE CENTIMETRES THICK AND 1.5 METRES ACROSS, WORKING TOGETHER TO COLLECT TENS OF MILLIONS OF TIMES AS MUCH LIGHT AS THE HUMAN EYE. AN ADDITIONAL 133 SEGMENTS HAVE BEEN PRODUCED TO FACILITATE THE MAINTENANCE AND RECOATING OF THE SEGMENTS ONCE THE telescope IS OPERATIONAL. ESO HAS ALSO PROCURED 18 SPARE SEGMENTS, BRINGING THE TOTAL NUMBER TO 949. NOW, GERMAN COMPANY SCHOTT HAS SUCCESSFULLY CAST THE BLANK FOR THE LAST OF THE 949 SEGMENTS, SEEN IN THIS PHOTO. THE M1 BLANKS, SHAPED PIECES OF MATERIAL THAT ARE LATER POLISHED TO BECOME THE MIRROR SEGMENTS, ARE MADE FROM ZERODUR©, A LOW-EXPANSION GLASS-CERAMIC MATERIAL DEVELOPED BY SCHOTT AND OPTIMISED FOR THE EXTREME TEMPERATURE RANGES AT THE ELT’S SITE IN THE ATACAMA DESERT. THE 949TH SEGMENT IS SEEN IN THIS IMAGE BEFORE BEING CUT INTO ITS HEXAGONAL SHAPE AND POLISHED — STEPS THAT WILL BE PERFORMED BY FRENCH COMPANY SAFRAN REOSC.

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CREDIT: SCHOTT

The European Southern Observatory’s Extremely Large Telescope (ESO’s ELT), under construction in the Chilean Atacama Desert, is one step closer to completion. German company SCHOTT has successfully cast the blank for the last of the 949 segments commissioned for the telescope’s primary mirror (M1). With a diameter of more than 39 metres, M1 will be by far the largest mirror ever made for a telescope.

Too large to be made from a single piece of glass, M1 will consist of 798 hexagonal segments, each about five centimetres thick and 1.5 metres across, working together to collect tens of millions of times as much light as the human eye. An additional 133 segments have been produced to facilitate the maintenance and recoating of the segments once the telescope is operational. ESO has also procured 18 spare segments, bringing the total number to 949. 

The M1 blanks, shaped pieces of material that are later polished to become the mirror segments, are made from ZERODUR©, a low-expansion glass-ceramic material developed by SCHOTT and optimised for the extreme temperature ranges at the ELT’s site in the Atacama Desert. This company has also manufactured the blanks of three other ELT mirrors — M2, M3, and M4 — at their facilities in Mainz, Germany. 

“What ESO ordered from SCHOTT is more than just ZERODUR©,” says Marc Cayrel, Head of ELT Optomechanics at ESO. “In close collaboration with ESO, SCHOTT fine-tuned every single production step, tailoring the product to meet and often exceed the ELT’s very demanding requirements. The outstanding quality of the blanks was maintained throughout the mass production of more than 230 tonnes of this super-performing material. ESO is thus very thankful for the professionalism of the skilled teams at SCHOTT, our trusted partner.”

Thomas Werner, ELT Project Lead at SCHOTT, says: “Our entire team is thrilled to conclude what has been the largest single order of ZERODUR® in the history of our company. For this project, we successfully concluded the serial production of hundreds of ZERODUR® mirror substrates, when we usually have a single-piece operation. It’s been an honour for all of us to play a part in shaping the future of astronomy.”

Once cast, all segments follow a multi-step, international journey. After a slow cooling and heat treatment sequence, the surface of each blank is shaped by ultra-precision grinding at SCHOTT. The blanks are then transported to French company Safran Reosc, where each of them is cut into an hexagon shape and polished to a precision of 10 nanometres across the entire optical surface — meaning the surface irregularities of the mirror will be less than one thousandth of the width of a human hair. Also involved in the work done on the M1 segment assemblies are: Dutch company VDL ETG Projects BV, which is producing the segment supports; the German-French FAMES consortium, which has developed and is finalising manufacturing for the 4500 nanometric-accuracy sensors monitoring the relative position of each segment; German company Physik Instrumente, which designed and is manufacturing the 2500 actuators able to position the segment to nanometric precision; and Danish company DSV, which is in charge of transporting the segments to Chile.

Once polished and assembled, each M1 segment is shipped across the ocean to reach the ELT Technical Facility at ESO’s Paranal Observatory in the Atacama Desert — a 10 000-kilometre journey that over 70 M1 segments have already completed. In Paranal, only a few kilometres away from the construction site of the ELT, each segment is coated with a silver layer to become reflective, after which it will be carefully stored until the telescope’s main structure is ready to receive them.

When it starts operating later this decade, ESO’s ELT will be the world’s largest eye on the sky. It will tackle the biggest astronomical challenges of our time and make as-yet unimaginable discoveries.

More information

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society. 

Links

• Find out more about ESO's Extremely Large Telescope (ELT)  on our dedicated website and press kit
• More detailed information on M1  
• More information on SCHOTT’s work on the ELT 
• For journalists: subscribe to receive our releases under embargo in your language

 

Ephemeral streams, often overlooked, are major contributors to US river flow and water quality

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

Ephemeral streams – temporary streams that only flow after rainfall or snowmelt – contribute more than 50% of the flow in downstream river systems and likely have a major influence on water quality across the United States, according to a new modeling study. The findings show how important ephemeral streams are for the transport of water and pollution into larger, more permanent water bodies. Excluding these streams from coverage under the U.S. Clean Water Act, say the authors, would significantly limit federal authority to protect downstream water quality. Ephemeral streams, which flow only in direct response to precipitation and are disconnected from groundwater sources, play a crucial role in transporting nutrients, sediments, pollutants, and other materials to larger water bodies. Although these short-lived streams likely account for much of the global river network, research focused specifically on ephemeral streams is limited, and their hydrological contributions to downstream flow and water quality remain largely unknown. Craig Brinkerhoff and colleagues developed a model to quantify ephemeral stream contributions to more than 20.7 million more permanent water bodies in the contiguous US. Brinkeroff et al. combined data from published hydrological datasets to estimate ephemeral stream locations, and when and how much they flow. The authors found that ephemeral streams in the southwest and western US flow less frequently (only 4 to 46 days per year on average) compared to those in the eastern US, where they flow 173 days per year on average. However, despite their infrequent flow, western ephemeral streams contributed more significantly to downstream river flow – as high as 79% on average – than eastern ephemeral streams, which contributed ~50% on average. Combined, the findings show that ephemeral streams contribute, on average, 55% of the flow to the perennially flowing rivers in the contiguous US. According to Brinkeroff et al., the findings show that ephemeral streams are likely a substantial pathway through which pollution enters rivers, lakes, reservoirs, and ultimately the ocean. “Even though the ephemeral channels are often overlooked because of their infrequent flow, they are critical to downstream water availability,” write Judson Harvey and Stephanie Kampf in a related Perspective. “Climate- and land use-driven changes will alter flows and related functions of ephemeral streams in ways that influence future outcomes for water supply, drinking water quality, and the health of aquatic ecosystems in streams and rivers of all sizes.”

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JOURNAL

Science

DOI

10.1126/science.adg9430 

ARTICLE TITLE

Ephemeral stream water contributions to United States drainage networks

ARTICLE PUBLICATION DATE

28-Jun-2024

 

Pacific cod can’t rely on coastal safe havens for protection during marine heat waves, OSU study finds

OREGON STATE UNIVERSITY

 

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JUVENILE PACIFIC COD

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CREDIT: COURTESY OF BEN LAUREL, NOAA ALASKA FISHERIES SCIENCE CENTER

During recent periods of unusually warm water in the Gulf of Alaska, young Pacific cod in near shore safe havens where they typically spend their adolescence did not experience the protective effects those areas typically provide, a new Oregon State University study found.

Instead, during marine heat waves in 2014-16 and 2019, young cod in these near shore “nurseries” around Kodiak Island in Alaska experienced significant changes in their abundance, growth rates and diet, with researchers estimating that only the largest 15-25% of the island’s cod population survived the summer. Even after the high temperatures subsided, the cod have yet to return to pre-heat wave size and diet.

The findings, published today in the journal Scientific Reports, may have broader implications for marine fish populations worldwide, as marine heat waves become longer and more frequent with climate change, the researchers said.

“These coastal habitats aren’t supporting fish in the same way that they used to as a result of marine heat waves,” said lead author Hillary Thalmann, a graduate student in OSU’s Department of Fisheries, Wildlife and Conservation Sciences. “That’s a novel finding, because we don’t always look at the nurseries as a place where size-selective mortality could be occurring rapidly.”

Pacific cod, a popular choice for fish and chips, is the second-largest commercial groundfish fishery off the coast of Alaska. The 2022 commercial harvest totaled 403 million pounds and was valued at $225 million, according to NOAA Fisheries. Cod also has a long history in Alaskan culture and is important to Indigenous communities in the region.

The nurseries are shallow areas along shorelines with lots of aquatic vegetation, including eelgrass, algae and kelp, which attract lots of food for the fish and provide hiding places where they can avoid predators. Typically, they are considered safe havens for small Pacific cod — areas where the fish go at around 3 months old to eat and grow as much as they can during their first summer and fall.

But during the two recent marine heat waves in the Gulf of Alaska, water temperatures were recorded at 58 degrees Fahrenheit, almost 6 degrees above normal. Together, the two heat waves are considered the most extreme warming events on record in the Northeast Pacific Ocean, and the effects on the cod population were so severe that the fishery was closed in 2020 and a federal disaster was declared in 2022.

Previous OSU research has found that the higher temperatures triggered earlier reproduction and high mortality among young Pacific cod. The new study focuses on the physiological disruptions the young cod experienced while occupying the coastal nurseries.

Researchers used juvenile Pacific cod collected by the NOAA Alaska Fisheries Science Center Fisheries Behavioral Ecology program from 16 sites around Kodiak Island in mid-July and late August for the years 2006-2019. This sampling was part of routine population monitoring for the cod fishery.

For the July sample, researchers looked at the fishes’ otoliths, tiny bony structures that chronicle a fish’s growth similar to the rings of trees. Measuring the otoliths allowed researchers to calculate the fishes’ precise rate of growth up to the July sampling date, and then calculate their projected size based on maintaining that same growth rate into August.

However, when they looked at the August sample, the fish were 30% bigger than the size predicted by the established growth rate, and there were almost no small fish present in the sample. The only way researchers were able to account for the size of the fish in August was to remove all the small fish from the July sample and leave just the largest 15-25% of fish following the projected growth rate trajectory.

“If we removed the little guys and grew the big guys — the top 15-25% — through to August based on the growth rates we saw earlier in the summer, then we got the size range that we see in those heat wave years,” Thalmann said. “It’s important to show that with heat events like this, size-selective mortality can continue in the cod population beyond just their early life in the open water,” where the larvae spend their first three months.

Size-selective mortality is the phenomenon of survival being determined by an organism’s size; here, only the biggest fish appear to have survived. 

“We saw these differences in size in the nursery, and we tried to explain them with growth rates and tried to explain them with diet, but we couldn’t explain it all,” Thalmann said. “There was something out there, probably size-selective mortality, that was the major driver for what we were seeing.”

Moving forward, researchers say changing ocean conditions may mean that Pacific cod have to move further north to find optimal growth environments, or there may be a shift toward bigger cod being the only ones to survive and contribute genetic information to subsequent generations.

“If the marine heat waves continue, there will probably be some changes in both the distribution and the quality of these populations,” Thalmann said. “I don’t think it’s the end of fish and chips, but I do think it’s a cautionary tale for climate change and the shifting dynamics of fisheries in warm temperatures.”

Co-authors on the study were Zoe Almeida, Kaitlyn Osborne, Kaylee Marshall and Jessica Miller at OSU and Benjamin Laurel at the NOAA Alaska Fisheries Science Center in Newport, Oregon.

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JOURNAL

Scientific Reports

DOI

10.1038/s41598-024-63897-w 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Marine heatwaves alter the nursery function of coastal habitats for juvenile Gulf of Alaska Pacific cod

ARTICLE PUBLICATION DATE

27-Jun-2024

To protect corals from summer heatwaves, we should help their microbial symbionts evolve heat tolerance in the lab, researchers say

CELL PRESS

Most coral reef restoration efforts involve restocking reefs with nursery-grown corals. However, if these corals are of the same stock as their wild counterparts, they will be equally vulnerable to the heat stress that caused the bleaching event in the first place. In a review publishing June 27 in the journal Trends in Microbiology, researchers discuss the potential of improving corals’ chances by inducing the evolution of heat tolerance in their symbionts—the mutualistic microbes that provide corals with nutrients in exchange for shelter and that are expelled during coral bleaching.

“Although heat-tolerant and -sensitive symbiont species occur in nature, even corals that harbor naturally tolerant symbionts have been observed to bleach during summer heatwaves,” write the authors, a team of marine scientists and bioengineers from Australia and New Zealand, including senior author Madeleine van Oppen (@spectacularia) of the Australian Institute of Marine Science and the University of Melbourne. “Experimental evolution of Symbiodiniaceae offers a means to shift their thermal tolerance limit upward, increasing host resistance to bleaching.”

To induce the evolution of heat-tolerance, researchers culture coral symbionts in the lab and expose successive generations to gradually increasing temperature, which maintains a selective pressure, so with each new generation, more heat-tolerant individuals are more likely to survive and reproduce.

“A critical decision about the efficacy of this intervention will revolve around determining whether field-deployed corals inoculated with heat-evolved symbionts exhibit greater tolerance to summer heatwaves compared with their native counterparts because all observations so far have been made in the lab,” they write.

Methods for culturing the symbionts will also need to be scaled up dramatically if this strategy is to be used at the necessary scale. “Research cultures are typically in the milliliter to liter volumes, yet thousands of liters would be required to inoculate millions of coral recruits reared from multiple reefs or regions,” the authors write.

The authors note that researchers may fine tune culture conditions for mass production of Symbiodiniaceae by taking inspiration from large-scale culturing of microalgae for biotechnological applications (while preventing yield loss). Experimental evolution of Symbiodiniaceae would be most effective in coral restoration efforts if used in conjunction with other measures, such as assisted gene flow, managed breeding of corals, and manipulation of coral-associated bacteria.

“All these interventions will be critical in maximizing the likelihood that coral reefs persist into the future, but it is imperative that these occur in tandem with significant emissions reductions and science-based reef management,” they write.

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This research was supported by the Australian Research Council, the Paul G. Allen Family Foundation, and the Reef Restoration and Adaptation Program, and the Royal Society Te Apārangi.

Trends in Microbiology, Nitschke et al. “The use of experimentally evolved coral photosymbionts for reef restoration” https://www.cell.com/trends/microbiology/fulltext/S0966-842X(24)00139-2

Trends in Microbiology, (@TrendsMicrobiol) published by Cell Press, is a monthly review journal that provides a multidisciplinary forum for the discussion of all aspects of microbiology—from cell biology and immunology to genetics and evolution—and ranges across virology, bacteriology, protozoology, and mycology. Visit http://www.cell.com/trends/microbiology. To receive Cell Press media alerts, please contact press@cell.com.

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JOURNAL

Trends in Microbiology

DOI

10.1016/j.tim.2024.05.008 

METHOD OF RESEARCH

Literature review

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The use of experimentally evolved coral photosymbionts for reef restoration

ARTICLE PUBLICATION DATE

27-Jun-2024

 

Climate change and sea level rise pose an acute challenge for cities with combined sewer systems

Drexel University researchers provide a detailed look at impending storm water and sewer management problems for cities like Camden and Philadelphia

DREXEL UNIVERSITY

Older coastal cities, like Philadelphia, New York and Boston are at risk of being inundated by untreated sewage during floods. Due in part to the design of their combined sewer systems and in part due to sea level rise, these cities could be facing a growing public health crisis as climate change also drives more extreme precipitation, according to researchers at Drexel University who study urban stormwater management. The group recently published research that modeled the potential extent of the problem in a section of the coastal city of Camden, New Jersey, and the effectiveness of one proposed intervention to help protect these communities.

 

A Compounding Problem

Beginning in 1855 many of America’s coastal communities were designed with a combined sewer system. In these systems, stormwater and sewage are collected using the same pipes. Originally, these pipes discharged to streams and rivers; later they were directed toward wastewater treatment facilities. But the pipes can only convey a certain amount of flow. During wet weather events, to avoid inundating the wastewater treatment plants some portion of the flow still overflows into the natural water bodies through features known as combined sewer overflows – or CSOs.

While the Federal Pollution Control and Clean Water Act has pushed communities to upgrade their infrastructure and take steps to curtail CSOs, climate change brings an entirely new dimension to this regulatory compliance challenge.

When the water level in the receiving water body is high, the CSO flap gates that ordinarily keep river water from backing up into the sewer pipes can’t open as easily. Without these relief valves fully open, the combined sewage generated during wet weather can back up in the system, even spilling out onto the street or into people’s basements.

As climate change brings more heavy rain and higher river levels, the problem worsens and cannot be mitigated with conventional approaches to stormwater management.

“Climate change is making what was already a difficult problem even more challenging,” said Franco Montalto, PhD, a professor in the College of Engineering who led the research. “The combination of sea level rise and precipitation intensification is particularly difficult for urban stormwater managers because it means the combined sewer system is being loaded from both sides. In many cases, there’s no place for the water to go but up and out onto the street creating environmental and health risks.”

Montalto’s team has been working closely with the Camden County Municipal Utilities Authority (CCMUA) to study potential solutions to this problem.

 

Looking for a Better Answer

In their research, recently published in the Journal of Water Management Modeling, the group reported on the results of their detailed hydrologic and hydraulic models of flooding and combined sewer overflows in the Cramer Hill section of Camden. This is a flood-prone portion of the city located very close to the largest CSO point on the East side of the Delaware River.

Once they calibrated their models to historical conditions, they used them to simulate how flooding and CSOs would change in the future, as the climate changes. The same models are also being used to evaluate the potential effectiveness of different conceptual solutions.

“CCMUA has been working diligently for years to reduce environmental injustices in Camden,” Montalto said. “It has worked to reduce odors from its wastewater treatment plant and reduce the frequency and pollution associated with CSOs. It’s exciting to work with them now on the development of solutions that can also reduce flooding and make Camden’s neighborhoods more resilient to climate change. Our modeling will support CCMUA as it develops multifunctional infrastructure strategies.”

Drexel’s model is unique because it is an “all-pipes” model built by assembling many different geospatial data sets into one computer model. This allows the team to simulate stormwater flows through virtually every surface, catch basin, and pipe in the area.

To check the accuracy of the modeling program, the researchers compared the model’s prediction of annual combined sewer overflow discharge volume to CCMUA records. Simulated flood patterns were compared to photographs of actual floods taken by the research team during storms over the summer of 2021.

“It was important to perform a thorough validation process because we will be relying on this model to simulate future climate and infrastructure conditions,” Montalto said. “Not every municipality has been making recordings of all the necessary data to build a complete model, so part of this research was showing that the ad-hoc process we developed could reliably validate our model without some of the data it would normally require.”

 

Projecting Future Challenges

Montalto’s team used the validated model to simulate what would happen if precipitation increased by up to 30% and if the sea level rose by up to 1.8 meters. They simulated each of these climatic changes independently, and together.

The model projected that increased precipitation would result in overflow discharges 21-66% above the current annual discharge volume. And, although each of the sea-level-rise scenarios resulted in a reduction in the number of overflow events and annual overflow discharge, the duration of flooding increased with each compounding factor.

 

Testing a Theory

One key strategy that Camden has been considering for Cramer Hill’s water management challenges involves diverting upstream stormwater away from its sewer system. With Drexel’s modeling program, the municipality was finally able to test the idea.

Dubbed the “Pennsauken disconnection,” the suggestion is to divert stormwater generated in the town of Pennsauken, New Jersey, which is immediately northeast of Camden, away from Cramer Hill’s combined sewer system via an intermediary pumping station.

The team found that the disconnection will help under all future climate scenarios. However, even with the disconnection, the impacts of climate change and sea level rise still resulted in an increase in the number of flooding events; and a significant increase in the duration of flooding under the sea-level-rise conditions.

 

Setting a New Course

Overall, the results suggest that increased precipitation events due to climate change will cause more combined sewer overflows. And sea level rise will make it more difficult for these systems to discharge into nearby bodies of water. Some 40 million people currently live in areas served by combined sewer systems, so this is both a pressing issue and one that could affect a significant number of people throughout the country.

Montalto’s group plans to continue refining its Cramer Hill model, as they collect information about water flow through the sewage network and surface flooding. They will also model other infrastructure interventions to manage stormwater.

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JOURNAL

Journal of Water Management Modeling

DOI

10.14796/JWMM.C516 

METHOD OF RESEARCH

Computational simulation/modeling

ARTICLE TITLE

Opportunities for Leveraging Existing Hydrologic and Hydraulic Models Developed for Water Quantity Management to Mitigate Flooding Due to Extreme Precipitation