Bin Chen recognized with National Science Foundation CAREER Award

Bin Chen, assistant researcher in the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology, has received the National Science Foundation’s Faculty Early Career Development (CAREER) Award. As the most prestigious award for junior faculty from NSF, it is bestowed on teacher-scholars performing outstanding research and classroom education at the university level. Chen will be awarded $570,000 over a 5-year period for his project—Elasticity and Lattice Dynamics of Iron Alloys under Earth’s Core Conditions.

Residing at the center of the Earth, the core is the innermost and extremely dynamic region of our planet.

“Understanding the nature and dynamics of the core can deeply enhance our abilities in understanding the magnetic field generation process, the thermo-chemical evolution of the Earth’s deep interior, and the formation of the Earth as a habitable planet,” said Chen.

With this award, Chen will systematically measure properties of various iron alloys under extremely high temperatures and pressures nearly one million times greater than at the surface of the Earth, using a high-pressure device called diamond anvil cell and high-brilliance X-rays at synchrotron facilities. This will provide a new set of fundamental data on density, sound velocities and crystal properties of iron alloys under previously uncharted pressure-temperature regimes. This information is essential to further constraint the core’s composition and dynamics including how seismic (earthquake) waves travel through Earth’s deepest interior.

The involvement of student researchers will initiate the ‘pipeline’ that helps influence and attract a diverse student population, particularly traditionally underrepresented minorities, into Earth science and build diverse geoscience workforce.

This CAREER award will provide support for graduate and undergraduate student researchers to engage in high-pressure mineral physics research employing the state-of-the-art experimental techniques at departmental, university and national laboratories. For the education and outreach part of the project, Chen is building an inquiry-based Multi-Anvil Press Laboratory (MAPLab) teaching module for higher education and outreach to K–12 students and general public.

Since joining UH Mānoa in January of 2014, Chen has received a total of $570K in funding as a leading principal investigator. His overall work focuses on understanding physics and chemistry of Earth and planetary interiors. Recently he has been working on the deep carbon cycle in the Earth’s interior with a focus on carbon in Earth’s core.

More about Bin Chen

He received is bachelor’s degree in geochemistry from University of Science and Technology of China in 2001; a master’s degree in isotope geochemistry from University of Science and Technology of China in 2004 and a PhD degree in geology from the University of Illinois at Urbana-Champaign in 2009.

Research explains near-island biological hotspots in barren ocean basins

Coral reef islands and atolls in the Pacific are predominantly surrounded by vast areas of ocean that have very low nutrient levels and low ecological production. However, the ecosystems near these islands and atolls are often extremely productive and support an enhanced nearshore food-web, leading to an abundance of species and increased local fisheries. An international team of scientists from the National Oceanic and Atmospheric Administration (NOAA), University of Hawaii – Manoa (UHM), National Geographic Society, Scripps Institution of Oceanography, and Bangor University published a study in Nature Communications today which provides the first basin-scale investigation of this paradoxical increase in productivity near coral reef islands and atolls – referred to as the ‘Island Mass Effect’

“Surprisingly, scientists have historically known very little with respect to the prevalence, geographic variability, and drivers of this ecologically important phenomenon,” said Dr. Jamison Gove, lead author of the study and research oceanographer at the Ecosystems and Oceanography Program of NOAA’s Pacific Islands Fisheries Science Center (PIFSC).

Phytoplankton – the microscopic plants that live in sunlit seawater – form the base of the marine ecosystems, and dictate the distribution and production of fisheries in the Pacific and across the globe. Jamison Gove and colleagues studied 35 coral reef islands and atolls, using satellite imagery and ship-based surveys to assess the extent of the Island Mass Effect across the Pacific. Their analysis showed that localized increases in nearshore phytoplankton biomass are a near-ubiquitous feature among locations surveyed, creating biological ‘hotspots’ across the Pacific.

“Important services that ecosystems provide to human populations, such as fisheries production, can be intrinsically linked to nearshore phytoplankton enhancement associated with the Island Mass Effect,” said Dr. Margaret McManus, co-author of the study and oceanography professor at the UHM School of Ocean and Earth Science and Technology (SOEST).

The researchers further discovered that the strength of the Island Mass Effect varied between ecosystems, and that island type, sea-floor slope, reef area, and human habitation are the primary drivers of phytoplankton enhancement differences. Overall, the scientists found that the Island Mass Effect enhances phytoplankton biomass up to 86% over offshore ocean conditions, providing increased food resources for higher trophic groups such as tuna and dolphins.

Although increased phytoplankton is often beneficial for these ecosystems, it can also lead to toxic algal blooms, increased fleshy (non-reef building) algal growth, and other negative impacts when associated with human activities. The ability to discern human- versus natural-driven changes in phytoplankton biomass is of great scientific interest and has important resource management implications. “That humans can artificially elevate phytoplankton biomass – around entire islands – provides important context for the scale at which human activities on land can impact nearshore marine ecosystems.” said Gove. “The goal now is to better characterize human activities and their respective influence on nearshore phytoplankton production so that we can develop effective strategies that mitigate future impacts”

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Jamison M. Gove, Margaret A. McManus, Anna B. Neuheimer, Jeffrey J. Polovina, Jeffrey C. Drazen, Craig R. Smith, Mark A. Merrifield, Alan M. Friedlander, Julia S. Ehses, Charles W. Young, Amanda K. Dillon & Gareth J. Williams (2016). Near-island biological hotspots in barren ocean basins. Nature Communications, http://dx.doi.org/10.1038/ncomms10581.

New grant to investigate how bacteria induce settling and transformation of marine larvae

For more than 100 years, marine biologists have sought an understanding of how the minute larvae of marine invertebrate animals – cast out into the vast ocean – find and settle in the right ecological settings for survival, growth and reproduction. A grant, totaling more than $870,000, from the Gordon and Betty Moore Foundation to the University of Hawai‘i (UH) will support research to understand the mechanisms by which marine biofilm bacteria – bacteria that live in slime films on the surfaces of all objects submerged in the sea – induce the settling of larvae of marine invertebrate animals.

With this grant, a UH research team will focus on a small tube worm, Hydroides elegans, that settles onto marine surfaces in warm ocean waters around the world where they form masses of hard, calcified tubes. The team, led by professor Michael Hadfield at the Kewalo Marine Laboratory, Pacific Biosciences Research Center in the School of Ocean and Earth Science and Technology (SOEST) at UH-Mānoa (UHM), includes larval biologist Brian Nedved (Kewalo Marine Laboratory), microbiologist Rosie Alegado (Center for Microbial Oceanography: Research and Education, SOEST, UHM), and natural products chemist Shugeng Cao (Department of Pharmaceutical Sciences, Daniel K. Inouye College of Pharmacy, UH-Hilo).

Bacteria initiate dramatic transformation

In the last two decades there has been growing recognition that bacteria are likely the factor that causes many free-floating larvae to settle and transform, yet very little is known of the diversity of bacteria that stimulate larvae to settle, and less is known of the mechanisms through which these bacteria act.

“We have isolated specific strains of bacteria from marine biofilms that induce the worm’s larvae to settle and metamorphose. Using these bacteria, our goals are to determine what factors produced by the bacteria cause the larvae to stop swimming, stick to the surface and undergo the dramatic physical changes that make up the process of metamorphosis,” said Hadfield.

During the two-year project, Hadfield and colleagues will also study the larva’s receptor or response system. Understanding the relationship between the tube worm and bacteria will shed light on the complex phenomena that lead to the establishment and maintenance of healthy marine seafloor communities throughout the ocean.

Larvae are very particular in selecting surfaces on which they will settle – which is why different communities of invertebrate animals live on sandy beaches, rocky coasts, pilings and other surfaces in enclosed harbors.

“For many – probably most – of these animals, biofilm bacteria are the key. This research holds promise to reveal the basis for differential larval settlement in the sea,” said Hadfield.

Real world application

The current project arose from long-running research in Hadfield’s laboratory. In the lab, Hadfield has studied the biology of marine larvae and long ago established Hydroides elegans as a useful model organism for studying larval settlement and “biofouling” – the accumulation of undesirable organisms on marine surfaces.

Larva of barnacles, tube worms, oysters, and other organisms settle on ship hulls, pilings and in the pipes used to draw cooling water into electrical plants and factories resulting in millions of dollars in loss annually in these maritime trades. Knowing why larvae settle in particular places is an important first step in ensuring they do not settle where they are not wanted.

Moreover this work may have real-world application to areas such as mariculture, where the goal is to successfully raise larvae of clams and oysters and have them settle on a particular surface, as well as for the development of methods to deter larval recruitment onto the hulls of ships and other marine surfaces.

New experiments determine effective treatments for box jelly stings

Researchers at UH Mānoa have developed an array of highly innovative experiments to allow scientists to safely test first-aid measures used for box jellyfish stings – from folk tales, like urine, to state-of-the-art technologies developed for the military. The power of this new array approach, published this week in the journal Toxins, is in its ability to rigorously assess the effectiveness of various treatments on inhibiting tentacle firing and venom toxicity – two aspects of a sting that affect the severity of a person’s reaction.

Box jellyfish are among the deadliest creatures on Earth, and are responsible for more deaths than shark attacks annually. Despite the danger posed by these gelatinous invertebrates, scientists and medical professionals still do not agree on the best way to treat and manage jellyfish stings.

Dr. Angel Yanagihara collects Hawaiian box jellyfish (Alatina alata) at 3 am along Waikiki Beach, Honolulu, HI. Credit: UH

“Authoritative web articles are constantly bombarding the public with unvalidated and frankly bad advice for how to treat a jelly sting,” said Dr. Angel Yanagihara, lead author of the paper and assistant research professor at the UHM Pacific Biosciences Research Center (PBRC) and John A. Burns School of Medicine (JABSOM). “I really worry that emergency responders and public-health decision makers might rely on these unscientific articles. It’s not too strong to point out that in some cases, ignorance can cost lives.”

The results from Yanagihara and team’s rigorous testing demonstrate that tried-and-true methods, including vinegar and hot water immersion, really do work on Hawaiian box jellyfish (Alatina alata) stings. Further, the study shows that a new therapeutic, Sting No More^TM, developed by Yanagihara with Department of Defense funding, inhibits the venom directly.

Yanagihara, aided by Dr. Christie Wilcox, a postdoctoral fellow at JABSOM, set out to test which first-aid measures actually help reduce the venom delivered when a tentacle stings or lessen the harm caused by venom that has been injected. But because box jelly stings can be life threatening, experimentation on people was out of the question.

“What we needed were innovative models that would allow us to test how different options might affect the severity of a sting without putting anyone at risk,” Yanagihara said. “So we designed a set of experiments using live, stinging tentacles and live human red blood cells which allowed us to pit first-aid measures against one another.”

Blood cells destroyed by stinging cells create a clear halo around an Alatina alata tentacle (right) in the blood agarose model. (credit: Angel Yanagihara, ©Yanagihara Lab/Department of Defense H922)

The ultimate test compared the effects of treatments in a living sting model comprised of human red blood cells suspended in an agarose gel and covered with lanolin-rubbed sterile porcine intestine, which was used as a mock skin. The researchers found that the most effective treatments were Sting No More™ products and hot water, with Sting No More™ shown to work faster and better than hot water, according to the data.

“People think ice will help because jelly stings burn and ice is cold,” said Wilcox. “But research to date has shown that all marine venoms are highly heat sensitive. Dozens of studies, including our recent work, have shown that hot water immersion leads to better outcomes than ice.”

Wilcox hopes that the new experimental models will allow for more rigorous testing of first-aid measures for venomous stings from other species of Cnidaria. “The science to date has been scattered and disorganized,” she said. “We strived to design methods that were straightforward and inexpensive, so that others can use them easily. The field has suffered from a lack of standardized, rigorous and reproducible models. Our paper outlines a way to change that.”

While the current study only tested first-aid measures using the Hawaiian box jelly, the researchers said they are working on seeing how treatments work for stings from other common Hawaiian species, including the Portuguese Man O’ War that wash ashore on leeward shores during strong winds. And, they hope that they won’t be the only ones testing treatments with their experimental array.

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Sting No More™ (Alatalab Solutions, LLC) was developed under a Department of Defense grant that aimed to rapidly and effectively treat stings in US Special Operations Command combat divers. With the intention of supporting the development of technologies and therapies of benefit to people, the funding required a commercialization plan for resulting products. All testing of the new commercial product, in the current study was performed under an approved University of Hawai‘i Conflict of Interest plan. This product demonstrates the strongly pro-innovation culture at UH dedicated to bringing to the public sector technologies that have been developed with federal and state research dollars.

Honolulu Cookie Company and HIMB partner to save stranded whales and dolphins

The Honolulu Cookie Company announced a partnership with the Hawaiʻi Institute of Marine Biology to save stranded whales and dolphins in Hawaiʻi. The company will donate part of the proceeds from the sale of its Whale Collection cookies to support HIMB’s Marine Mammal Stranding Research and Rescue Initiative and is asking for the public’s support with HIMB’s research and conservation efforts.

Every year there are at least 25 reported strandings of marine mammals in Hawaiʻi. Many of these stranded mammals can be saved with sufficient volunteers and the facilities equipped to enable care and rehabilitation.

In 2016, HIMB will open operations in a new marine mammal-stranding center, also known as a whale and dolphin hospital, to respond to and rescue stranded marine mammals throughout the Hawaiʻian Islands. The hospital aims to save the 20 species of dolphins and whales found in Hawaiʻi, which are a crucial part of the state’s delicate marine ecosystem. HIMB’s care for and research of rescued whales and dolphins is only possible through the generosity of the public’s donations and support.

Every box of Honolulu Cookie Company’s Whale Collection cookies will include a special insert explaining HIMB’s Marine Mammal Stranding Research and Rescue Initiative and include a call-to-action to support HIMB’s conservation efforts. Additionally, Honolulu Cookie Company has partnered with HIMB to create a website to educate the public about the Institute’s research and rescue efforts—whale.soest.hawaii.edu. The company will also provide educational information about the program at their retail locations on Oʻahu and Maui.

To kick-start the initiative, Honolulu Cookie Company will donate $5,000 towards the research efforts of HIMB.

Get involved

The public can get involved and support HIMB’s efforts through donations. Visit whale.soest.hawaii.edu or call (808) 236-7401 for more information.

Another way for the public to get involved is to stop by Honolulu Cookie Company’s retail locations to get more information about this initiative.

Paul Nachtigall, PhD (HIMB) Aude Pacini, PhD (HIMB) and Herman Tam (Honolulu Cookie Company.) Photo courtesy: The Harris Agency.

Hawaii Institute of Marine Biology and Honolulu Cookie Company partner to save stranded whales and dolphins

Honolulu Cookie Company announces its partnership with the Hawaii Institute of Marine Biology (HIMB) to save stranded whales and dolphins in Hawaii. The Company will donate part of the proceeds from the sale of its Whale Collection cookies to support HIMB’s Marine Mammal Stranding Research and Rescue Initiative, and is asking for the public’s support with HIMB’s research and conservation efforts.

Every year there are at least 25 reported strandings of marine mammals in Hawaii. Many of these stranded mammals can be saved with sufficient volunteers and the facilities equipped to enable care and rehabilitation. In 2016, HIMB will open operations in a new marine mammal-stranding center, also known as a whale and dolphin hospital, to respond to and rescue stranded marine mammals throughout the Hawaiian Islands. The hospital aims to save the 20 species of dolphins and whales found in Hawaii, which are a crucial part of the state’s delicate marine ecosystem. HIMB’s care for and research of rescued whales and dolphins is only possible through the generosity of the public’s donations and support.

Every box of Honolulu Cookie Company’s Whale Collection cookies will include a special insert explaining HIMB’s Marine Mammal Stranding Research and Rescue Initiative and include a call-to-action to support HIMB’s conservation efforts. Additionally, Honolulu Cookie Company has partnered with HIMB to create a website to educate the public about the Institute’s research and rescue efforts: whale.soest.hawaii.edu. The Company will also provide educational information about the program at their retail locations on Oahu and Maui.

To kick-start the initiative, Honolulu Cookie Company will donate $5,000 towards the research efforts of HIMB.

The public can get involved and support HIMB’s efforts through donations. Visit whale.soest.hawaii.edu or call (808) 236-7401 for more information. Another way for the public to get involved is to stop by Honolulu Cookie Company’s retail locations to get more information about this initiative.

Beneficial bacteria in Hawaiian squid attracted to fatty acids

The small but charismatic Hawaiian bobtail squid is known for its predator-fooling light organ. To survive, the nocturnal cephalopod depends on a mutually beneficial relationship with the luminescent bacterium, Vibrio fischeri, which gives it the ability to mimic moonlight on the surface of the ocean, and deceive monk seals and other predators that would happily make a meal of the small creature.

A study published recently in Applied and Environmental Microbiology by Edward “Ned” Ruby, professor at the Pacific Biosciences Research Center and colleagues from the University of Wisconsin–Madison revealed that Vibrio fischeri has a novel type of receptors that sense the presence and concentration of fatty acids, a building block of all cell membranes. This class of receptors allows a bacterium to migrate toward short-chain fatty acids—a phenomenon referred to as chemotaxis.

The newly discovered fatty-acid sensors are not required for the bacterium to initiate symbiosis with the squid. Thus, the ability to migrate towards fatty acids appears to play a critical role in some other aspect of the bacterium’s life history.

“Interestingly, in Vibrio fischeri the gene encoding the receptor has duplicated, so that the cell has two copies of similar, and apparently functionally identical, genes. Such genetic investment in this receptor suggests that the ability to sense and migrate toward fatty acids may be important in the pathogenicity of other Vibrio species like Vibrio cholera [which causes cholera], Vibrio vulnificus [which causes necrotizing skin infections and gastroenteritis] and others,” said Ruby.

All organisms, even humans, use chemotaxis to attract beneficial microbes to specific tissues. For example, as human infants are exposed to bacteria in their environment, they must attract desirable species to particular tissues—gut, skin, teeth, reproductive tract—that must be colonized by these bacteria. Understanding how this colonization takes place will lead to greater understanding of how Earth’s many microbiomes become constructed and, thus allow us to better construct and manage them.

Read more at UH News, Star-Advertiser (subscription required), and Hawaii Public Radio.

Beneficial bacteria in Hawaiian squid attracted to fatty acids

A study published recently by Edward (Ned) Ruby, professor at UH Mānoa’s Pacific Biosciences Research Center (PBRC), and colleagues from the University of Wisconsin – Madison (UWM) revealed that Vibrio fischeri has novel receptors that sense the presence and concentration of fatty acids, a building block of all cell membranes. This class of receptors allows a bacterium to migrate toward short-chain fatty acids – a phenomenon referred to as chemotaxis.

“This is the first example of a receptor for this class of compounds, and this receptor appears to have evolved in, and be restricted to, the Vibrionaceae family of marine bacteria,” said Ruby.

Sending and receiving chemical signals allow bacteria to communicate with other organisms, gather information about their environment, and determine with whom to create a mutually beneficial partnership – a symbiosis. For example, the Hawaiian bobtail squid hatchlings aren’t born with Vibrio fischeri. They attract it, and only it, from the surrounding seawater using chemoattractants, and capture it in their light organs.

However, the newly discovered fatty-acid sensors are not required for the bacterium to initiate symbiosis with the squid. Thus, the ability to migrate towards fatty acids appears to play a critical role in some other aspect of the bacterium’s life history.

“Interestingly, in Vibrio fischeri the gene encoding the receptor has duplicated, so that the cell has two copies of similar, and apparently functionally identical, genes. Such genetic investment in this receptor suggests that the ability to sense and migrate toward fatty acids may be important in the pathogenicity of other Vibrio species like Vibrio cholera [which causes cholera], Vibrio vulnificus [which causes necrotizing skin infections and gastroenteritis] and others,” said Ruby.

In the future, Ruby and colleagues will continue to try and discover the attractants that allow Vibrio fischeri to be the only bacterial species that can colonize the light organ of the squid. With only one species to track, it is easier to study the colonization process than when there are dozens or hundreds of bacterial species that are needed to colonize the tissue (like the gut).

Understanding how this colonization takes place will lead to greater understanding of how Earth’s many microbiomes become constructed and, thus allow us to better construct and manage them.

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K. Nikolakakis, K. Monfils, S. Moriano-Gutierrez, C.A. Brennan and E.G. Ruby (2015). Characterization of the fatty-acid chemoreceptors VfcB and VfcB2 from Vibrio fischeri, Applied and Environmental Microbiology, doi: 10.1128/AEM.02856-15.

Novel tsunami detection network uses navigation systems on commercial ships

Accurate and rapid detection and assessment of tsunamis in the open ocean is critical for predicting how they will impact distant coastlines, enabling appropriate mitigation efforts. Scientists from the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST) are using commercial ships operating in the North Pacific to construct a network of low-cost tsunami sensors to augment existing detection systems.

Local and global partnership

The researchers, funded by NOAA, are partnering with Matson, Maersk Line and the World Ocean Council to equip 10 ships with real-time geodetic GPS systems and satellite communications. The newly built pilot network of GPS-equipped ships enables each vessel to act as an open-ocean tide gauge. Data from these new tsunami sensors are streamed, via satellite, to a land-based data center where they are processed and analyzed for tsunami signals.

“Matson was an obvious partner for this project due to their long history in Hawaiʻi and shared interest in community safety and coastal hazards,” said James Foster, SOEST associate researcher and lead investigator for the project. “The World Ocean Council’s unique connection within the industry allowed us to bring Maersk Line into the collaboration.”

New approach strengthens existing network

“The unexpectedly huge 2011 Tohoku, Japan earthquake and the unanticipated type of fault slip which caused the 2012 event at Queen Charlotte Islands, Canada highlighted weaknesses in our understanding of earthquake and tsunami hazards and emphasized the need for more densely-spaced observing capabilities,” said Foster.

Despite the advances in tsunami monitoring and modeling technology over the last decade, there are too few observations of tsunamis to provide sufficiently accurate predictions required for hazard response agencies to be able to make the best possible response to tsunami events. In particular, there are very few sensors in the deep ocean between the tsunami source and the distant coastlines that might be threatened. The sensors that do exist are expensive to build and maintain, so only a limited number are deployed. Gaps in the coverage of the network, as well as routine outages of instruments, limit the ability of the current detection system to accurately assess the hazard posed by each event.

“Our approach offers a new, cost-effective way of acquiring many more observations to augment the current detection networks,” said co-investigator Todd Ericksen, SOEST assistant specialist.

Right place, right time, right equipment

By chance, in 2010, UH Mānoa researchers discovered that the ship-based global navigation satellite systems aboard the UH research vessel Kilo Moana were able to detect and measure the properties of tsunamis in the open ocean, thus paving the way for the current project. Foster and colleagues were running an experiment using geodetic GPS on the R/V Kilo Moana when the tsunami generated by the magnitude 8.8 earthquake in Maule, Chile (February 27, 2010) passed the ship. Analysis of the data proved that the system accurately recorded the tsunami signal.

Improving predictions

The researchers are working with the NOAA Tsunami Warning Centers to ensure that the network provides the most useful data products to help them with their predictions. They will be working with their industry collaborators to develop a new version of the shipboard package that can be deployed on a much greater number of ships.

“Our new ship-based detection network is the first step towards the creation of the dense global observing network needed to support the efforts of tsunami warning centers to provide the best possible predictions of tsunami hazard to coastal communities,” said Foster.

Evidence for mixing and layering of Earth’s interior clarifies debate

Earth’s mantle, the large zone of slow-flowing rock that lies between the crust and the planet’s core, powers every earthquake and volcanic eruption on the planet’s surface. There has been a long-standing debate in the geosciences on whether the lower and upper mantles are different in composition, and what such a difference would mean for mantle dynamics. A study published this week in Science Advances suggests that mixing due to mantle flow indeed occurs on a global scale, but discrete layers where material with similar composition has aggregated are nevertheless maintained.

Whereas the composition of Earth’s upper mantle can be estimated from lava outpourings on the ocean floor at mid-ocean ridges, the lower mantle remains poorly understood. Chemical observations indicate that the composition of the lower mantle may be different from the composition of the upper mantle. On the contrary, seismic tomography – creating images of Earth’s interior using earthquake-generated waves – provides evidence that the whole mantle is stirred, and presumably well-mixed.

Many huge slabs of ocean crust that have been dragged down, or subducted, into the mantle can still be detected in the deep Earth. These slabs slowly sink downward toward the bottom of the mantle. Some slabs sink all the way down, providing evidence for global stirring of the mantle by a process called “whole-mantle convection.” A large number of these slabs have stalled out and appear to float 1,000 kilometers deep, indicating a notable change in physical properties with depth. Lead author of the study, Maxim Ballmer, senior scientist at ETH Zurich and a former postdoctoral fellow at UH Mānoa’s School of Ocean and Earth Science and Technology (SOEST), and colleagues exploited this natural phenomenon to gain insight into a region no human or machine can reach.

Ballmer and researchers from University of Maryland, Japan Agency for Marine-Earth Science and Technology, and University of Michigan used a computer model of a simplified Earth. Each run of the model began with a slightly different chemical composition — and thus a different range of densities — in the mantle at various depths. The researchers then used the model to investigate how slabs of ocean crust would behave as they travel down toward the lower mantle.

They discovered that the layering – with slightly denser material in the lower mantle than in the upper mantle – can explain the “floating” of some slabs at ~1000 km depth. The authors suggest the lower mantle may be a mix of rock types, but enriched in some intrinsically denser rock type. The most likely candidate, they say, is subducted mid-ocean ridge basalt that has accumulated in the lower mantle over hundreds of million years. Basalt is ultimately picked up by mantle plumes, hot rising columns of mantle rock that sustain surface hotspots of volcanism such as on the Big Island of Hawai‘i – exemplifying the mantle’s true nature as the ultimate recycler.

The finding that the mantle may be layered led to another conundrum: How can the layering survive for geologic timescales of billions of years, as slabs continuously sink through the mantle and cause global-scale mixing? To answer this question, Ballmer and co-authors set up another model of global convection, which simulates the evolution of the Earth over 4½ billion years.

“Surprisingly, the models showed that moderate mantle layering can be sustained, even in the presence of whole-mantle convection,” said Ballmer. “Layering can be sustained by “unmixing” of rocks with different density – similar to an oil and water mixture separating over time. This unmixing competes with mixing during mantle convection.” Thus, whole-mantle convection and moderate layering of rock types are not mutually exclusive, contrary to previous thinking.

In the future, Ballmer and colleagues will assess the combined effects viscosity and density. If the rock types in the mantle not only differ in density, but also in viscosity (like water and crude oil, or water and honey), this should have strong effects on mixing as well as “unmixing” processes. For example, in the extreme case, high-viscosity rocks will never be mixed, like plums in the pudding.

“If the lower mantle has a different viscosity than the upper mantle, the related feedback on mantle convection and mixing may affect our understanding of Earth evolution,” Ballmer said.

Researchers are indeed just beginning to decipher the messages from the deep mantle, and its role in global recycling, which may have been key to maintain stable and life-friendly conditions on the Earth’s surface over the past billions of years.

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Maxim Ballmer, Nicholas Schmerr, Takashi Nakagawa and Jeroen Ritsema (2015). Compositional mantle layering revealed by slab stagnation at ~1000-km depth, Science Advances. DOI: 10.1126/sciadv.1500815