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)
Friday, June 25, 2021
Influence of land use on soil erosion in European Russia for the last 30 years
A comprehensive study of this large region of Russia saw light in Water
IMAGE: CHANGE IN THE TOTAL AREA OF CULTIVATED LAND (F) IN THE RUSSIAN FEDERATION IN 1970-2017. RSFSR--THE RUSSIAN SOVIET FEDERATIVE SOCIALIST REPUBLIC AS THE PRINCIPAL PART OF THE FORMER USSR UNTIL... view more
CREDIT: KAZAN FEDERAL UNIVERSITY
Research Associate Artyom Gusarov studied a vast array of erosion data to make a general takeaway that soil erosion and river sediment load in the aforementioned region has significantly decreased throughout the post-Soviet period.
"The decrease has been especially profound in the forest steppe, a part of which covers the Republic of Tatarstan, because of the combined influence of climate change and land cultivation," explains Gusarov. "To the north of the forest steppe, in the southern part of the boreal zone, the anthropogenic factor was the primary influence on the changes in soil erosion, at least in the east of the East European Plain. Here, the reduction of cultivated land was the biggest in the post-Soviet time. In the steppes, the primary role can be attributed to climate change, especially the warming of the near-soil air, which led to decreased frosting of soils during winters, and, therefore, decreased erosion-inducing sediment from tillage."
The research shows that there is a complex intertwining between seemingly negative socio-economic developments and environmental conditions.
"The recession of agriculture in contemporary Russia, including decreases in tillage areas, numbers of agricultural machines, livestock population, etc., led to decreased soil and ravine erosion in the region, decreased river sediment load and concomitant pollution," says Gusarov.
The results are very important for the comprehensive planning of soil preservation, hydrogeological construction, and artificial water bodies. Artyom Gusarov aims to continue this research, now moving to the northern part of the East European Plain and the rivers running into the Arctic Ocean.
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Asian elephants do more than just trumpet -- they buzz their lips to squeak
The animals' sound production does not only come from the trunk
IMAGE: WITH THE ACOUSTIC CAMERA´S STAR-SHAPED ARRAY OF MICROPHONES PLACED IN FRONT OF THE ELEPHANT THE RESEARCHERS ARE WAITING PATIENTLY FOR HER TO VOCALIZE WHILE NIGHT FALLS. view more
Everybody from a child knows that elephants trumpet. Over the past decades research in general and at the University of Vienna has mainly studied the elephants low-frequency rumble. Its fundamental frequency reaches into the infrasonic range below the human hearing threshold. This call is produced by the elephant´s massive vocal folds. Much less was known about how elephants produce their higher pitched sounds, trumpets and squeaks.
The following rule generally applies to sound production in mammals: the larger the vocal fold, the lower the calls fundamental frequency. Conversely the size of the vocal folds sets an upper limit to the fundamental frequencies that can be reached. The high-pitched squeak only Asian but not African elephants produce when aroused, do not fit within that spectrum.
In her recent study Veronika Beeck, who is part of the FWF doctorate school Cognition and Communication at the Department of Behavioural and Cognitive Biology at the University of Vienna and her supervisor Angela Stöger, together with Gunnar Heilmann and Micheal Kerscher from gfai tech, Berlin, studied the squeak sounds of Asian elephants in Nepal.
The researchers used an acoustic camera with an array of 48 microphones that visualises sounds in colours similar to a thermic camera. In this way the sound source was precisely located. "Our images clearly demonstrate that the squeaks are emitted by the mouth and not the trunk", Veronika Beeck explains.
According to the researcher's theory the Asian elephants produce squeaks by pressing air through their tensed lips inducing the lip´s vibration. This technique equals the human brass players lip buzzing to produce a complex sound whose harmonic overtones are subsequently resonated by the instrument, resulting in its characteristic brassy sound. "Apart from human brass players this technique of lip buzzing to produce sounds has, to our knowledge, not been described in any other animal species and is thus considered unique in the animal kingdom", says Veronika Beeck.
The elephants iconic trumpet on the other hand is produced by a blast of air through the trunk. Here again, however, the vibrating anatomic sound source is not yet conclusively studied.
This new evidence further highlights the elephant´s flexibility in sound production. A few years ago, Angela Stöger-Horwath showed that elephants are capable of learning novel sounds. An Asian elephant in a Korean Zoo, by imitating his trainer, learned to speak some words in Korean. Since only a few elephants in this recent study squeaked the researchers suggest that squeaks might be learned, too.
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Publication in BMC Biology: A novel theory of Asian elephant high-frequency squeak production. Veronika C. Beeck, Gunnar Heilmann, Michael Kerscher, Angela S. Stoeger DOI: BMCB-D-20-01049
The origins of farming insects
Ambrosia fungi cultivated by beetles for more than 100 million years
IMAGE: THE AMBROSIA BEETLE CROSSOTERASUS EXTERNEDENTATUS (CURCULIONIDAE: PLATYPODINAE). view more
CREDIT: BJARTE JORDAL, UNIVERSITY OF BERGEN (NORWAY)
A beetle bores a tree trunk to build a gallery in the wood in order to protect its lay. As it digs the tunnel, it spreads ambrosia fungal spores that will feed the larvae. When these bore another tree, the adult beetles will be the transmission vectors of the fungal spores in another habitat. This mutualism among insects and ambrosia fungi could be more than 100 years old --more than what was thought to date-- according to an article published in the journal Biological Reviews.
The study analyses for the first time the symbiotic associations and the coevolution between ambrosia fungi and beetles from a paleontological perspective using the Cretaceous fossil records of these biological groups. Among the authors of the study are the experts David Peris and Xavier Delclòs, from the Faculty of Earth Sciences and the Biodiversity Research Institute of the University of Barcelona (IRBio), and Bjarte Jordal, from the University of Bergen (Norway).
Beetles that grew fungi millions of years before human agriculture
Some termites, ants and beetles developed the ability to grow fungi in order to eat millions of years ago. This mutualism between insects and fungi --one of the top studied symbiosis in the natural field-- is an analogous evolutionary strategy in the farming activities of the human species since the Neolithic revolution.
Understanding the origins of the symbiosis between insects and fungi is a field of interest in several scientific disciplines. Nowadays, the mutualism between ambrosia symbiont beetles and fungi is the cause of forest and crop plagues that cause serious ecological and economic losses "it remains unclear which ecological factors facilitated the origin of fungus farming and how it transformed into a symbiotic relationship with obligate dependency", notes David Peris, first author of the study.
When did the lineage of farming insects begin?
Historically, phylogenetic studies suggest beetle fungiculture started more than 50 million years ago --before other insects-- and some studies dated it back to 86 million years ago. "The symbiotic relationship between fungus and beetles would have probably originated more than 100 million years ago, during the early Cretaceous, in groups of beetles that had gone unnoticed", reveals the expert David Peris.
As part of the study, the experts studied several specimens of worldwide distribution of the biological groups captured in amber from the Cretaceous. Therefore, the origin of ambrosia fungus is older than the main groups of beetles from the subfamilies Scolytinae and Platypodinae --Curculionidae family-- which now grow fungus in tree trunks, as stated by the authors.
"This suggests that these fungi used some other group of insects to spread millions of years ago", notes the researcher. Also, other beetle groups with a similar behaviour to ambrosia beetles --Bostrichidae and mostly Lymexylidae families-- present an older and abundant fossil record that would coincide with the emergence of ambrosia fungi, according to previous studies.
"The most interesting thing --he continues-- is that some studies note the ability to cultivate fungi in some of these current species".
Evolutionary convergence towards an obligate mutualism
The growing process of fungi starts when beetles colonize a new tree trunk or branch. During the Cretaceous, the abundance of fungi and wood-boring beetles facilitated a starting domestication of some groups of fungi. First, the fungal spores were accidentally transported from tree to tree by the wood-boring beetles "until this mutually beneficial association evolved towards a more intimate symbiosis in which fungi were inoculated into to a tree, the fungal mycelia grew and beetle larvae fed from the fungus", notes Bjarte Jordal.
This set of factors, together with the symbionts' high ability to adapt and change, eased the morphological and ecological adaptations of biological groups that converged in an obligated mutualism. That is, a symbiotic relationship between insects and fungi, beneficial for both, which still lasts.
"However, we need more studies on the knowledge of the ecology of the species from the Lymexylidae and Bostrichidae families to get more specific conclusions. Therefore, the discovery of new fossils in cretaceous amber of these groups will certainly help us to better understand the evolutionary history of this symbiotic relationship that still exists nowadays", concludes Professor Xavier Delclòs.
CAPTION
The holotype of the species Raractocetus fossilis (Lymexylidae).
CREDIT
Shuhei Yamamoto
New research reveals remarkable resilience of sea life in the aftermath of mass extinctions
IMAGE: AT THE CRETACEOUS-PALEOGENE BOUNDARY, NOT ONLY DINOSAURS WENT EXTINCT. THE LOSS OF SPECIES IN THE UPPER PART OF THE OCEAN HAD PROFOUND IMPACTS ON ITS DIVERSITY AND FUNCTION. IMAGE SHOWS... view more
CREDIT: BRIAN HUBER
Pioneering research has shown marine ecosystems can start working again, providing important functions for humans, after being wiped out much sooner than their return to peak biodiversity.
The study, led by the University of Bristol and published today in Proceedings of the Royal Society B, paves the way for greater understanding of the impact of climate change on all life forms.
The international research team found plankton were able to recover and resume their core function of regulating carbon dioxide levels in the atmosphere more than twice as fast as they regained full levels of biodiversity.
Senior author Daniela Schmidt, Professor of Palaeobiology at the University of Bristol, said: "These findings are hugely significant, given growing concern around the extinctions of species in response to dramatic environmental shifts. Our study indicates marine systems can accommodate some losses in terms of biodiversity without losing full functionality, which provides hope. However, we still don't know the precise tipping point so the focus should very much remain on preserving this fragile relationship and protecting biodiversity."
While previous research has shown that functionality resumes quicker than biodiversity in algae, this is the first study to corroborate the discovery further up the food chain in zooplankton, which are vital for sea life as part of the food web supporting fish.
The scientists analysed tiny organisms called foraminifer, the size of grains of sand, from the mass extinction, known as the Cretaceous-Paleogene (K-Pg), which took place around 66 million years ago and eradicated three-quarters of the Earth's plant and animal species. This is the most catastrophic event in the evolutionary history of modern plankton, as it resulted in the collapse of one of the ocean's primary functions, the 'biological pump' which sucks vast amounts of carbon dioxide out of atmosphere into the ocean where it stays buried in sediments for thousands of years. The cycle not only influences nutrient availability for marine life, but also carbon dioxide levels outside the sea and therefore the climate at large.
Lead author Dr Heather Birch, a former researcher at the university's School of Earth Sciences and Cabot Institute for the Environment, said: "Our research shows how long - approximately 4 million years - it can take for an ecosystem to fully recover after an extinction event. Given human impact on current ecosystems, this should make us mindful. However, importantly the relationship between marine organisms and the marine carbon pump, which affects atmosphere CO2, appears not to be closely related."
Professor Schmidt added: "The results highlight the importance of linking climate projections with ecosystems models of coastal and open ocean environments to improve our ability to understand and forecast the impact of climate-induced extinctions on marine life and their services to people, such as fishing. Further research is needed to look at what happens and whether the same patterns are evident higher up the food web, for instance with fish."
CAPTION
Image shows large diverse Cretaceous fauna before the extinction.
CREDIT
Brian Huber
Paper
'Ecosystem Function after the K/Pg Extinction: Decoupling of Marine Carbon Pump and Diversity' in Proceedings of the Royal Society B by Heather Birch, Daniela Schmidt, Helen Coxall, Dick Croon, and Andrew Ridgewell
Notes to editors
Professor Daniela Schmidt is available for interview. To arrange this, please email d.schmidt@bristol.ac.uk and Victoria Tagg, Media & PR Manager (Research) at the University of Bristol: victoria.tagg@bristol.ac.uk
Photos
https://fluff.bris.ac.uk/fluff/u2/oc20541/bZfApSp3FrzHFwVf49ZJlQ1RO/ At the Cretaceous-Paleogene boundary, not only dinosaurs went extinct. The loss of species in the upper part of the ocean had profound impacts on its diversity and function. Image shows small deprived Cretaceous fauna after the extinction. Photo credit: Brian Huber
IMAGE: SINK HOLES AND LIQUEFACTION ON ROADS IN CHRISTCHURCH, NEW ZEALAND AFTER 2011 EARTHQUAKE. view more
CREDIT: MARTIN LUFF, CC BY-SA 2.0, VIA WIKIMEDIA COMMONS
Our homes and offices are only as solid as the ground beneath them. When that solid ground turns to liquid -- as sometimes happens during earthquakes -- it can topple buildings and bridges. This phenomenon is known as liquefaction, and it was a major feature of the 2011 earthquake in Christchurch, New Zealand, a magnitude 6.3 quake that killed 185 people and destroyed thousands of homes.
An upside of the Christchurch quake was that it was one of the most well-documented in history. Because New Zealand is seismically active, the city was instrumented with numerous sensors for monitoring earthquakes. Post-event reconnaissance provided a wealth of additional data on how the soil responded across the city.
"It's an enormous amount of data for our field," said post-doctoral researcher, Maria Giovanna Durante, a Marie Sklodowska Curie Fellow previously of The University of Texas at Austin (UT Austin). "We said, 'If we have thousands of data points, maybe we can find a trend.'"
Durante works with Prof. Ellen Rathje, Janet S. Cockrell Centennial Chair in Engineering at UT Austin and the principal investigator for the National Science Foundation-funded DesignSafe cyberinfrastructure, which supports research across the natural hazards community. Rathje's personal research on liquefaction led her to study the Christchurch event. She had been thinking about ways to incorporate machine learning into her research and this case seemed like a great place to start.
"For some time, I had been impressed with how machine learning was being incorporated into other fields, but it seemed we never had enough data in geotechnical engineering to utilize these methods," Rathje said. "However, when I saw the liquefaction data coming out of New Zealand, I knew we had a unique opportunity to finally apply AI techniques to our field."
The two researchers developed a machine learning model that predicted the amount of lateral movement that occurred when the Christchurch earthquake caused soil to lose its strength and shift relative to its surroundings.
CAPTION
Large-scale lateral spreading displacement maps for the 22 February 2011 Christchurch earthquake. (a) Displacements observed from optical image correlation (after Rathje et al., 2017b), and displacements predicted by Random Forest (RF) classification models using (b) Model 3 (No CPT data) and (c) Model 5 (CPT data).
CREDIT
Maria Giovanna Durante and Ellen M Rathje, UT Austin
"It's one of the first machine learning studies in our area of geotechnical engineering," Durante said.
The researchers first used a Random Forest approach with a binary classification to forecast whether lateral spreading movements occurred at a specific location. They then applied a multiclass classification approach to predict the amount of displacement, from none to more than 1 meter.
"We needed to put physics into our model and be able to recognize, understand, and visualize what the model does," Durante said. "For that reason, it was important to select specific input features that go with the phenomenon we study. We're not using the model as a black box-- we're trying to integrate our scientific knowledge as much as possible."
Durante and Rathje trained the model using data related to the peak ground shaking experienced (a trigger for liquefaction), the depth of the water table, the topographic slope, and other factors. In total, more than 7,000 data points from a small area of the city were used for training data -- a great improvement, as previous geotechnical machine learning studies had used only 200 data points.
They tested their model citywide on 2.5 million sites around the epicenter of the earthquake to determine the displacement. Their model predicted whether liquefaction occurred with 80% accuracy; it was 70% accurate at determining the amount of displacement.
The researchers used the Frontera supercomputer at the Texas Advanced Computing Center (TACC), one of the world's fastest, to train and test the model. TACC is a key partner on the DesignSafe project, providing computing resources, software, and storage to the natural hazards engineering community.
Access to Frontera provided Durante and Rathje machine learning capabilities on a scale previously unavailable to the field. Deriving the final machine learning model required testing 2,400 possible models.
"It would have taken years to do this research anywhere else," Durante said. "If you want to run a parametric study, or do a comprehensive analysis, you need to have computational power."
She hopes their machine learning liquefaction models will one day direct first-responders to the most urgent needs in the aftermath of an earthquake. "Emergency crews need guidance on what areas, and what structures, may be most at risk of collapse and focus their attention there," she said.
Sharing, Reproducibility, and Access
For Rathje, Durante, and a growing number of natural hazard engineers, a journal publication is not the only result of a research project. They also publish all of their data, models, and methods to the DesignSafe portal, a hub for research related to the impact of hurricanes, earthquakes, tsunamis, and other natural hazards on the built and natural environment.
"We did everything on the project in the DesignSafe portal," Durante said. "All the maps were made using QGIS, a mapping tool available on DesignSafe, using my computer as a way to connect to the cyberinfrastructure."
For their machine learning liquefaction model, they created a Jupyter notebook -- an interactive, web-based document that includes the dataset, code, and analyses. The notebook allows other scholars to reproduce the team's findings interactively, and test the machine learning model with their own data.
"It was important to us to make the materials available and make it reproducible," Durante said. "We want the whole community to move forward with these methods."
This new paradigm of data-sharing and collaboration is central to DesignSafe and helps the field progress more quickly, according Joy Pauschke, program director in NSF's Directorate for Engineering.
"Researchers are beginning to use AI methods with natural hazards research data, with exciting results," Pauschke said. "Adding machine learning tools to DesignSafe's data and other resources will lead to new insights and help speed advances that can improve disaster resilience."
Advances in machine learning require rich datasets, precisely like the data from the Christchurch earthquake. "All of the information about the Christchurch event was available on a website," Durante said. "That's not so common in our community, and without that, this study would not have been impossible."
Advances also require high-performance computing systems to test out new approaches and apply them to new fields.
The researchers continue to refine the machine learning model for liquefaction. Further research, they say, is needed to develop machine learning models that are generalizable to other earthquake events and geologic settings.
Durante, who returned to her native Italy this year, says one thing she hopes to take back from the U.S. is the ability for research to impact public policy.
She cited a recent project working with Scott Brandenberg and Jonathan Stewart (University of California, Los Angeles) that developed a new methodology to determine whether a retaining wall would collapse during an earthquake. Less than three years after the beginning of their research, the recommended seismic provisions for new buildings and other structures in the U.S. included their methodology.
"I want my work to have an impact on everyday life," Durante said. "In the U.S., there is more of a direct connection between research and real life, and that's something that I would like to bring back home."
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These sea anemones have a diverse diet. And they eat an
A study describes the gut contents of giant plumose anemones off the coast of the state of Washington
IMAGE: THE GIANT PLUMOSE ANEMONE METRIDIUM FARCIMEN. view more
CREDIT: CREDIT: CHRISTOPHER WELLS, AS PUBLISHED IN ENVIRONMENTAL DNA (HTTPS://ONLINELIBRARY.WILEY.COM/DOI/FULL/10.1002/EDN3.225)
BUFFALO, N.Y. -- The giant plumose anemone is an animal, but it looks a bit like an underwater cauliflower. Its body consists of a stalk-like column that attaches to rocks and other surfaces on one end, and to a crown of tentacles on the other.
The anemones use these feelers to collect and shove food into their mouths, and a new study provides an in-depth look into the rich diversity of prey the anemones are catching. This includes a surprising menu item: ants, specifically the pale-legged field ant, Lasius pallitarsis. And the occasional spider.
The research was published on June 15 in the journal Environmental DNA. The study focused on giant plumose anemones, known to scientists as Metridium farcimen, that were fixed to the sides and undersides of floating docks in the region of the San Juan Archipelago in the northwestern part of the state of Washington.
The team used a method called DNA metabarcoding to identify the gut contents of a dozen giant plumose anemones. The species' diet was heavy on arthropods, especially crabs (presumably larvae, researchers say), and also included barnacles (larvae or molts), copepods and insects.
"We've greatly expanded the list of things we know that they eat. They're eating whatever they can catch, whatever isn't too big or too small, whatever can't swim away," says first author Christopher Wells, PhD, a postdoctoral researcher in the University at Buffalo Department of Geology. "One of the most surprising results is that in addition to all the usual suspects you'd find in marine plankton, we also found that a part of the diet, about 10% at the time of the study, consisted of ants, which are not marine."
By digging into the natural history of the pale-legged field ant, the researchers came up with a possible explanation for how these ants became part of the marine food chain.
"It's timed with the reproductive portion of the lifespan," Wells says, noting that the study was conducted during the month of August, when the ants have mating flights. "They produce winged queens and drones, which mate and make new colonies. They're not strong fliers and the wind pushes them around, potentially into the water."
The team's results indicate that giant plumose anemones also eat the occasional hapless spider, along with a few insects in addition to ants that may wander too close to the water's edge and drown.
The study was a collaboration between Wells; Gustav Paulay, PhD, at the Florida Museum of Natural History; Bryan Nguyen, PhD, at George Washington University; and Matthieu Leray, PhD, at the Smithsonian Tropical Research Institute. Wells, now in the Department of Geology in the UB College of Arts and Sciences, conducted the research at Friday Harbor Laboratories while completing a PhD at the University of Washington.
By extracting genetic material from a slushy mix of partially digested food, the researchers were able to work backward, comparing their results to information stored in databases about the DNA of varied organisms.
"Part of our research was using this method, DNA metabarcoding, and comparing it to traditional techniques where you wash out or cut open an anemone and then identify what you can see. The trouble is when you do that, you can't identify everything," Wells says. "You might say, 'That looks like it's a copepod antenna,' but you can't tell what species it is.
With DNA metabarcoding, you can identify what species' antennae that is. We were able to identify a lot more diversity using metabarcoding."
Knowing what an animal eats is indispensable when trying to understand how marine communities function.
"When a plankton community floats overtop a bed of anemones, the plankton is filtered by millions of grasping tentacles," Wells says. "This can drastically change the composition of the plankton community, which is food for many economically important animals such as bivalves and fish."
Anemones found in close proximity to one another had varied diets, but, "I don't think that's because they're choosing different things to eat," Wells says. "They eat what they can, and it's very patchy what they get, depending on what's there."
While the researchers were able to identify many of the species preyed on by the giant plumose anemone, Paulay, curator of invertebrate zoology at the Florida Museum of Natural History, noted they were unable to match a substantial portion of DNA sequences with any known organisms, underscoring how much is left to be discovered in the oceans.
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The research was supported by the Robert T. Paine Experimental and Field Ecology Award Fellowship; Friday Harbor Laboratories Research Fellowship Endowment and Marine Science Fund; Patricia L. Dudley Endowment for Friday Harbor Laboratories; Richard and Megumi Strathmann Fellowship; and Kenneth P. Sebens Endowed Student Support Fund.
Elephant seal diving mystery solved: 24-hour feeding could be climate change sentinel
CREDIT: PHOTO BY TAIKI ADACHI (NIPR/UNIVERSITY OF ST ANDREWS)
Female elephant seal weigh on average 350 kg, and dive continuously to the ocean's mesopelagic zone, about 200 to 1,000 meters deep, to consume their only prey: small fish that weigh less than 10 grams. Now, an international team of researchers, armed with eight years of data, may have answered a decades-long question: How do seals maintain their large size on such small prey?
"It is not easy to get fat," said paper author Taiki Adachi, research fellow with the National Institute of Polar Research and the School of Biology, University of St Andrews. "Elephant seals have to spend almost the whole day -- 20 to 24 hours every day -- deep diving to feed on many small fish and gain body fat stores, which is essential for successful reproduction."
The researchers outfitted 48 female elephant seals with data loggers that tracked everything from location and depth to jaw motion and seal buoyancy, which helps estimate the rate of fat gain. The loggers also used video to capture prey type. They tracked the seals during their two-month post-breeding short migrations in the Northeast Pacific Ocean between 2011 and 2018.
"We focused on this time after breeding because gaining fat energy stores is critical in their annual life cycles to determine whether they will pup again in the next breeding year, ultimately affecting population dynamics," Adachi said.
With more than five million feeding events recorded, the researchers found that, on average, a single seal dove 80 to 100% of the day -- that's about 60 dives a day -- to eat anywhere from 1,000 to 2,000 fish and gain more calories than they burned.
"We suggest that female elephant seals, which are not capable of echolocation or filter-feeding like other large marine mammals, found a unique evolutionary pathway to enhance diving abilities relative to their body mass, allowing them to dive continuously to the mesopelagic depths and maximize feeding opportunities on abundant small fishes," Adachi said. "These results demonstrate the close relationships between body size, prey availability and hunting capacity that shape the foraging guilds within marine animals."
While the elephant seals adapted to a unique foraging niche, according to Adachi, the adaptation may also put the elephant seals at risk as ocean temperatures rise and potentially reduce prey availability.
"We suggest that the narrow behavioral niche of elephant seals severely constrains their plasticity to buffer changes in mesopelagic fish biomass," Adachi said. "The round-the-clock foraging suggest that elephant seals are vulnerable to reduction in prey abundance." The researchers plan to continue studying elephant seals' foraging activity and monitoring their fat gain rate as an indicator of prey abundance changes.
"The next step is studying elephant seals as an important living sentinel to reveal climate change effect on deep ocean ecosystems," Adachi said.
Co-authors include Akinori Takahashi and Yasuhiko Naito, National Institute of Polar Research; Daniel P. Costa, Patrick W. Robinson, Sarah H. Peterson, Rachel R. Holser and Roxanne S. Beltran, Department of Ecology and Evolutionary Biology, University of California Santa Cruz; Luis A. Hückstädt, Institute of Marine Sciences, University of California Santa Cruz; Theresa R. Keates, Department of Ocean Sciences, University of California Santa Cruz. Costa and Peterson are also affiliated with the Institute of Marine Sciences, University of California Santa Cruz. Hückstädt is also affiliated with the Department of Biology and Marine Biology, University of North Carolina Wilmington.
The Japan Society for the Promotion of Science, the Office of Naval Research and the E&P Sound and Marine Life Joint Industry Project of the International Association of Oil and Gas Producers funded this work.
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About National Institute of Polar Research (NIPR)
The NIPR engages in comprehensive research via observation stations in Arctic and Antarctica. As a member of the Research Organization of Information and Systems (ROIS), the NIPR provides researchers throughout Japan with infrastructure support for Arctic and Antarctic observations, plans and implements Japan's Antarctic observation projects, and conducts Arctic researches of various scientific fields such as the atmosphere, ice sheets, the ecosystem, the upper atmosphere, the aurora and the Earth's magnetic field. In addition to the research projects, the NIPR also organizes the Japanese Antarctic Research Expedition and manages samples and data obtained during such expeditions and projects. As a core institution in researches of the polar regions, the NIPR also offers graduate students with a global perspective on originality through its doctoral program. For more information about the NIPR, please visit: https://http://www.nipr.ac.jp/english/
About the Research Organization of Information and Systems (ROIS)
The Research Organization of Information and Systems (ROIS) is a parent organization of four national institutes (National Institute of Polar Research, National Institute of Informatics, the Institute of Statistical Mathematics and National Institute of Genetics) and the Joint Support-Center for Data Science Research. It is ROIS's mission to promote integrated, cutting-edge research that goes beyond the barriers of these institutions, in addition to facilitating their research activities, as members of inter-university research institutes.
Antarctic Circumpolar Current flows more rapidly in warm phases
In future the intensity of the Antarctic Circumpolar Current could increase, accelerating climate change
ALFRED WEGENER INSTITUTE, HELMHOLTZ CENTRE FOR POLAR AND MARINE RESEARCH
Our planet's strongest ocean current, which circulates around Antarctica, plays a major role in determining the transport of heat, salt and nutrients in the ocean. An international research team led by the Alfred Wegener Institute has now evaluated sediment samples from the Drake Passage. Their findings: during the last interglacial period, the water flowed more rapidly than it does today. This could be a blueprint for the future and have global consequences. For example, the Southern Ocean's capacity to absorb CO2 could decrease, which would in turn intensify climate change. The study has now been published in the journal Nature Communications.
The Antarctic Circumpolar Current (ACC) is the world's strongest ocean current. Since there are no landmasses blocking its way, the West Wind Drift drives the water unhindered eastwards around the Antarctic in a clockwise direction. As a result, a gigantic ring-shaped current forms, linking together the Pacific, Atlantic and Indian Oceans in the south. The ACC is the central distribution point in global ocean circulation - also known as the 'global conveyor belt' - and as such influences oceanic heat transport and marine material cycles around the planet. Major changes in the ACC therefore have global consequences.
"Although the ACC plays an important role in tomorrow's climate, our understanding of its behaviour is still extremely limited," says Dr Shuzhuang Wu, a researcher at the Marine Geosciences Section of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and first author of the study released in Nature Communications. "In order to remove the related uncertainties in the climate models and to improve future forecasts, we urgently need paleo-data, which we can use to reconstruct the conditions and behaviour of the ACC in the past."
The only constriction on the ACC's circular route is the Drake Passage between the southern tip of South America and the Northern tip of the Antarctic Peninsula. Here, no less than 150 million cubic metres of ocean water per second force their way through the Passage - more than 150 times the amount of water flowing in all of Earth's rivers. This bottleneck is an ideal place to observe changes in the overall current. Accordingly, in 2016, AWI researchers travelled to the Drake Passage on board the research icebreaker Polarstern to investigate the sediment deposits from past millennia. "The bottom current here is so strong that in many places the sediment is simply washed away," explains the leader of the expedition and co-author of the study, Dr Frank Lamy. "Nevertheless, using the Polarstern's sediment echo sounder, we were able to detect the pockets of sediment and collect samples, including a core from a depth of 3,100 meters, measuring more than 14 metres in length. This was a significant achievement, since the last comparable cores from the Drake Passage dated back to the 1960s."
The sediments from the new core accumulated over the last 140,000 years. As such, they cover an entire glacial-interglacial cycle, and contain information from the last glacial period, which began 115,000 years ago and ended 11,700 years ago, as well as from the preceding Eemian interglacial period, which began 126,000 years ago.
By analysing the particle size in the deposited sediments, the research team was able to reconstruct the flow speed and the volume of water transported by the ACC in the Drake Passage. Based on the high percentage of small particles at the height of the last glacial period, the researchers calculated that the speed was slower compared to today, and there was a significantly smaller volume of water. This was due to the weaker westerlies and the more extensive sea ice in the Passage. This means that during the glacial period, the ACC's main driver blew more weakly, and the area of exposed water was smaller. In contrast, the extremely large particles at the height of the interglacial period indicated a high flow speed and a flow rate 10-15 percent higher than today.
"At the height of the last interglacial period from 115,000 to 130,000 years before today, the global temperature was on average 1.5° to 2° C warmer than it is today. Accordingly, the Circumpolar Current could accelerate as global warming progresses," says Lamy. "That would have far-reaching effects on the climate. On the one hand, the ACC shapes other ocean currents like the Gulf Stream, which in turn plays a role in determining the weather in Northwest Europe. On the other, the oceans absorb roughly a third of the surplus CO2 from the atmosphere. However, a more rapid ACC would promote the transport of CO2-rich deep water to the surface. Accordingly, the ocean's capacity to absorb atmospheric CO2 could decline significantly, and the concentration in the air could rise more quickly. In the long term, large parts of the Southern Ocean could even become sources of CO2."
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Original publication:
Shuzhuang Wu, Lester Lembke-Jene, Frank Lamy, Helge W. Arz, Norbert Nowaczyk, Wenshen Xiao, Xu Zhang, H. Christian Hass, Ju?rgen Titschack, Xufeng Zheng, Jiabo Liu, Levin Dumm, Bernhard Diekmann, Dirk Nu?rnberg, Ralf Tiedemann, Gerhard Kuhn: Orbital- and millennial-scale Antarctic Circumpolar Current variability in Drake Passage over the past 140,000 years. Nature Communications (2021), DOI: 10.1038/s41467-021-24264-9
