China honors Oregon State researcher for decade of scientific collaboration

CORVALLIS, Ore. — Major advances against some of the world’s most devastating plant diseases are starting to emerge from more than a decade of international scientific collaboration led by Brett Tyler, director of the Center for Genome Research and Biocomputing at Oregon State University. Tyler has fostered collaborative research in China, the United States and Europe on a group of organisms that cause diseases such as late blight in potatoes and soybean root rot. Both diseases cost millions of dollars in annual crop losses worldwide.

The joint research activities have advanced food production by understanding how plants such as potatoes and soybeans resist disease and how the genes responsible for resistance can be incorporated into new varieties. Potatoes developed by European researchers that incorporate these findings are just starting to hit commercial markets, and research is continuing on soybean diseases in the U.S. and China.

The People’s Republic of China recognized Tyler on Sept. 29 for his achievements with its highest civic award for non-Chinese scientists. Tyler, who is also a professor in the Department of Botany and Plant Pathology, received the Friendship Award of China for a decade of technical assistance and scientific collaboration with researchers at Nanjing Agricultural University and other Chinese institutions.

“It’s a wonderful bridge across the Pacific with the joint objective of increasing food security,” Tyler said.

Tyler, holder of the Stewart Chair in Gene Research, coordinates a worldwide research program on plant pathogens known to scientists as oomycetes. He and his colleagues have identified plant genes that confer long-term resistance to these pathogens. Scientists have focused on plant and pathogen genetics because the diseases can be so devastating, and pesticides tend to be rapidly evaded by these adaptable organisms.

“I have been working with an expanding circle of collaborators in China,” said Tyler, who has traveled to China 13 times. “We have published papers in top journals and established a growing collaborative research program.” In addition to his collaboration with researchers in Nanjing, he has worked with scientists at the Northwest Agricultural and Forestry University, Tsinghua University, the Beijing Genome Institute, Shandong Agricultural University and Yangzhou University.

Tyler’s Chinese partners — especially Yuanchao Wang at Nanjing and Weixing Shan at the NW Agricultural and Forestry University — have formed a consortium in China to apply the results of their disease resistance work in soybean and potato breeding. At the same time, Tyler has developed a similar network involving 19 institutions in the United States. With funding from the U.S. and Chinese governments, labs on both sides of the Pacific have hosted exchange students, jointly planned experiments and shared data.

“During our ten years of cooperation, Brett has helped to guide our research,” said Wang. “Research on the molecular genetics of oomycetes in China started from our cooperation. Brett helped us set up a great platform of genetic transformation and bioinformatics in Nanjing, and many other groups in China learned how to do this research from my group.”

The Chinese government has invested heavily in research in the last decade, added Tyler. “Our colleagues in China now have research facilities that are equal to or surpass what we have available in the United States,” he said.

Genes that provide long-term resistance to oomycete diseases are just starting to emerge in commercially available crops. “Resistance genes have been used in breeding for a long time, but many of them have been quickly defeated by the pathogens,” said Tyler. “We’ve uncovered why that happens. The pathogen produces a group of proteins that the plant has learned to detect. Unfortunately, these are proteins that the pathogen can quickly change. Now we have started to identify proteins the pathogen cannot change.”

In 2011, the USDA awarded $9.3 million to Tyler and his colleagues to apply their research to the U.S. soybean crop. Tyler’s Chinese collaborators are also contributing to that project. Soybean root rot causes major crop losses in China.


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Brett Tyler, 541-737-3686

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Brett Tyler

Study documents early warming of West Antarctica at end of last ice age

CORVALLIS, Ore. – West Antarctica began emerging from the last ice age about 22,000 years ago – well before other regions of Antarctica and the rest of the world, according to a team of scientists who analyzed a two-mile-long ice core, one of the deepest ever drilled in Antarctica.

Scientists say that changes in the amount of solar energy triggered the warming of West Antarctica and the subsequent release of carbon dioxide (CO2) from the Southern Ocean amplified the effect and resulted in warming on a global scale, eventually ending the ice age.

Results of the study were published this week in the journal Nature. The authors are all members of the West Antarctic Ice Sheet Divide project, which was funded by the National Science Foundation.

The study is significant because it adds to the growing body of scientific understanding about how the Earth emerges from an ice age. Edward Brook, an Oregon State University paleoclimatologist and co-author on the Nature study, said the key to this new discovery about West Antarctica resulted from analysis of the 3,405-meter ice core.

“This ice core is special because it came from a place in West Antarctica where the snowfall is very high and left an average of 20 inches of ice or more per year to study,” said Brook, a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “Not only did it allow us to provide more accurate dating because we can count the layers, it gave us a ton more data – and those data clearly show an earlier warming of the region than was previously thought.”

Previous studies have pointed to changes in the Earth’s orbit around the sun as the initial trigger in deglaciation during the last ice age. An increase in the intensity of summer sunlight in the northern hemisphere melted ice sheets in Canada and Europe starting at about 20,000 years ago and is believed to have triggered warming elsewhere on the globe.

It previously was thought that Antarctica started its major warming a few thousand years later, at about 18,000 years before present. However, the new study shows that at least part of Antarctica started to warm 2,000 to 4,000 years before this. The authors hypothesize that changes in the total amount of sunlight in Antarctica and melt-back of sea ice caused early warming at this coastal site – warming that is not recorded by ice cores in the interior of the continent.

“The site of the core is near the coast and it conceivably feels the coastal influence much more so than the inland sites where most of the high-elevation East Antarctic cores have been drilled,” Brook said. “As the sunlight increased, it reduced the amount of sea ice in the Southern Ocean and warmed West Antarctica. The subsequent rise of CO2 then escalated the process on a global scale.”

“What is new here is our observation that West Antarctica did not wait for a cue from the Northern Hemisphere before it began warming,” Brook said, “What hasn’t changed is that the initial warming and melting of the ice sheets triggered the release of CO2 from the oceans, which accelerated the demise of the ice age.”

Brook said the recent increase in CO2 via human causes is also warming the planet, “but much more rapidly.”

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Ed Brook, 541-737-8197; brook@geo.oregonstate.edu

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Researchers use circulation models, genetics to track “lost years” of turtles

CORVALLIS, Ore. – When green turtles toddle out to the ocean after hatching from eggs at sandy beaches they more or less disappear from view and aren’t seen again for several years until they show up as juveniles at coastal foraging areas.

Researchers have long puzzled over what happens to the turtles during these “lost years,” as they were dubbed decades ago. Now a new study published in the Proceedings of the Royal Society outlines where they likely would be based on ocean currents.

It is the first quantitative estimate of juvenile turtle distribution across an entire ocean basin and experts say it is significant because it gives researchers in North America, South America, Europe and Africa an idea of where hatchlings that emerge on beaches will go next, and where the juveniles foraging along the coastlines most likely came from.

“Hatchling sea turtles are too small for transmitters and electronic tags, and their mortality rate is sufficiently high to make it cost-prohibitive anyway,” said Nathan F. Putman, a post-doctoral researcher at Oregon State University and lead author on the study. “Even if you could develop a perfect sensor, you would need tens of thousands of them because baby turtles get gobbled up at such a fast rate. So we decided to look at an indirect approach.”

Putman and his colleague, Eugenia Naro-Maciel of City University of New York, used sophisticated ocean circulation models to trace the likely route of baby green turtles from known nesting sites once they entered the water. They also identified known locations of foraging sites where the turtles reappeared as juveniles, and went backwards – tracing where they most likely arrived via currents.

“This is not a definitive survey of where turtles go – it is more a simplification of reality – but it is a starting point and a big and comprehensive starting point at that,” Putman pointed out. “Turtles have flippers and can swim, so they aren’t necessarily beholden to the currents. But what this study provides is an indication of the oceanic environment that young turtles encounter, and how this environment likely influences turtle distributions.

“When we compared the predictions of population connectivity from our ocean current model and estimates from a genetic model, we found that they correlate pretty well,” said Putman, a researcher in OSU’s Department of Fisheries and Wildlife. “Each approach, individually, has limitations but when you put them together the degree of uncertainty is substantially reduced.”

The researchers simulated the dispersal of turtles from each of 29 separate locations in the Atlantic and West Indian Ocean and identified “hot spots” throughout these basins where computer models suggest that virtual turtles would be densely aggregated. This includes portions of the southern Caribbean, the Sargasso Sea, and portions of the South Atlantic Ocean and the West Indian Ocean.

In contrast, they estimate that the fewest number of turtles would be located in the open ocean along the equator between South America and central Africa.

Based on the models, it appears that turtles from many populations would circumnavigate the Atlantic Ocean basin. “Backtracking” simulations revealed that numerous foraging grounds were predicted to have turtles arrive from the North Atlantic, South Atlantic and Southwest Indian oceans. Thus, a high degree of connectivity among populations appears likely based on circulation patterns at the ocean surface.

Putman said the next step in the research might be for turtle biologists throughout the Atlantic Ocean basin to “ground truth” the model by looking for young turtles in those hotspots. Knowing more about their early life history and migration routes could help in managing the population, he said.

“Perhaps the best part about this modeling is that it is a testable hypothesis,” Putman said. “People studying turtles throughout the Atlantic basin will have predictions of turtle distributions based on solid oceanographic data to help interpret what they are observing.

“Finding these little turtles is like looking for the proverbial needle in the haystack,” Putman added. “But at least we’ve helped researchers understand where that haystack most likely would be located.”

Putman also has a study coming out in Biology Letters using similar methodology to predict ocean distribution patterns for the Kemp’s ridley sea turtle.

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Nathan Putman, 205-218-5276; Nathan.putman@oregonstate.edu

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Hatchling green turtle


Distribution of turtles
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Study finds novel worm community affecting methane release in ocean

CORVALLIS, Ore. – Scientists have discovered a super-charged methane seep in the ocean off New Zealand that has created its own unique food web, resulting in much more methane escaping from the ocean floor into the water column.

Most of that methane, a greenhouse gas 23 times more potent than carbon dioxide at warming our atmosphere, is likely consumed by biological activity in the water, the scientists say. Thus it will not make it into the atmosphere, where it could exacerbate global warming. However, the discovery does highlight scientists’ limited understanding of the global methane cycle – and specifically the biological interactions that create the stability of the ocean system.

Results of the study, which was funded primarily by the National Oceanic and Atmospheric Administration and the Federal Ministry of Education and Research in Germany, have just been published online in the journal Limnology and Oceanography.

“We didn’t discover any major ‘burps’ of methane escaping into the atmosphere,” said Andrew R. Thurber, a post-doctoral researcher at Oregon State University and lead author on the study. “However, some of the methane seeps are releasing hundreds of times the amounts of methane we typically see in other locations, so the structure and interactions of this unique habitat certainly got our attention.

“What made this discovery most exciting was that it is one of the first and best examples of a direct link between a food web and the dynamics that control greenhouse gas emissions from the ocean,” Thurber added.

The scientists first discovered this new series of methane seeps in 600 to 1,200 meters of water off North Island of New Zealand in 2006 and 2007. The amount of methane emitted from the seeps was surprisingly high, fueling a unique habitat dominated by polychaetes, or worms, from the family Ampharetidae.

"They were so abundant that the sediment was black from their dense tubes,” Thurber pointed out.

Those tubes, or tunnels in the sediment, are critical, the researchers say. By burrowing into the sediment, the worms essentially created tens of thousands of new conduits for methane trapped below the surface to escape from the sediments. Bacteria consumes much of the methane, converting it to carbon dioxide, and the worms feast on the enriched bacteria – bolstering their healthy population and leading to more tunnels and subsequently, greater methane release.

The researchers say that there is one more critical element necessary for the creation of this unique habitat – oxygen-rich waters near the seafloor that the bacteria harness to consume the methane efficiently. The oxygen also enables the worms to breathe better and in turn consume the bacteria at a faster rate.

“In essence, the worms are eating so much microbial biomass that they are shifting the dynamics of the sediment microbial community to an oxygen- and methane-fueled habitat – and the worms’ movements and grazing are likely causing the microbial populations to eat methane faster,” said Thurber, who works in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “That process, however, also leads to more worms that build more conduits in the sediments, and this can result in the release of additional methane.”

Methane seeps and worm communities are present in many other areas around the world, the researchers point out, including the Pacific Northwest. However, the deep water in many of these locations has low levels of oxygen, which the scientists think is a factor that constrains the growth of the worm populations. In contrast, the study sites off New Zealand are bathed in cold, oxygen-rich water from the Southern Ocean that fuels these unique habitats.

“The large amounts of methane consumed by bacteria have kept it from reaching the surface,” Thurber said. “Those bacteria essentially are putting the pin back in the methane grenade. But we don’t know if the worms ultimately may overgraze the bacteria and overtax the system. It’s something we haven’t really seen before.”

Also participating in the study were scientists from Scripps Institution of Oceanography, the National Institute of Water and Atmospheric Research in Wellington, New Zealand, and the Helmholtz Centre for Ocean Research in Germany.

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Andrew Thurber, 541-737-8251; athurber@coas.oregonstate.edu

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Worm feeding


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Worm outside its tube



Worm bed off coast

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Pass the salt: Common condiment could enable new high-tech industry

CORVALLIS, Ore. – Chemists at Oregon State University have identified a compound that could significantly reduce the cost and potentially enable the mass commercial production of silicon nanostructures – materials that have huge potential in everything from electronics to biomedicine and energy storage.

This extraordinary compound is called table salt.

Simple sodium chloride, most frequently found in a salt shaker, has the ability to solve a key problem in the production of silicon nanostructures, researchers just announced in Scientific Reports, a professional journal.

By melting and absorbing heat at a critical moment during a “magnesiothermic reaction,” the salt prevents the collapse of the valuable nanostructures that researchers are trying to create. The molten salt can then be washed away by dissolving it in water, and it can be recycled and used again.

The concept, surprising in its simplicity, should open the door to wider use of these remarkable materials that have stimulated scientific research all over the world.

“This could be what it takes to open up an important new industry,” said David Xiulei Ji, an assistant professor of chemistry in the OSU College of Science. “There are methods now to create silicon nanostructures, but they are very costly and can only produce tiny amounts.

“The use of salt as a heat scavenger in this process should allow the production of high-quality silicon nanostructures in large quantities at low cost,” he said. “If we can get the cost low enough many new applications may emerge.”

Silicon, the second most abundant element in the Earth’s crust, has already created a revolution in electronics. But silicon nanostructures, which are complex structures much smaller than a speck of dust, have potential that goes far beyond the element itself.

Uses are envisioned in photonics, biological imaging, sensors, drug delivery, thermoelectric materials that can convert heat into electricity, and energy storage.

Batteries are one of the most obvious and possibly first applications that may emerge from this field, Ji said. It should be possible with silicon nanostructures to create batteries – for anything from a cell phone to an electric car – that last nearly twice as long before they need recharging.

Existing technologies to make silicon nanostructures are costly, and simpler technologies in the past would not work because they required such high temperatures. Ji developed a methodology that mixed sodium chloride and magnesium with diatomaceous earth, a cheap and abundant form of silicon.

When the temperature reached 801 degrees centigrade, the salt melted and absorbed heat in the process. This basic chemical concept – a solid melting into a liquid absorbs heat – kept the nanostructure from collapsing.

The sodium chloride did not contaminate or otherwise affect the reaction, researchers said. Scaling reactions such as this up to larger commercial levels should be feasible, they said.

The study also created, for the first time with this process, nanoporous composite materials of silicon and germanium. These could have wide applications in semiconductors, thermoelectric materials and electrochemical energy devices.

Funding for the research was provided by OSU. Six other researchers from the Department of Chemistry and the OSU Department of Chemical Engineering also collaborated on the work.

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David Xiulei Ji, 541-737-6798

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Silicon nanostructure

Silicon nanostructures

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Table salt

Study explains Pacific equatorial cold water region

CORVALLIS, Ore. – A new study published this week in the journal Nature reveals for the first time how the mixing of cold, deep waters from below can change sea surface temperatures on seasonal and longer timescales.

Because this occurs in a huge region of the ocean that takes up heat from the atmosphere, these changes can influence global climate patterns, particularly global warming.

Using a new measurement of mixing, Jim Moum and Jonathan Nash of the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University have obtained the first multi-year records of mixing that permit assessment of seasonal changes. This is a significant advance beyond traditional shipboard measurements that are limited to the time that a ship can be away from port. Small instruments fueled by lithium batteries were built to be easily deployed on deep-sea equatorial moorings.

Moum employs a simple demonstration to show how mixing works.

He pours cold, white cream into a clear glass mug full of hot, black coffee, very carefully, using a straw to inject the heavier cream at the bottom of the mug, where it remains.

“Now we can wait until the cream diffuses into the coffee, and we’ll have a nice cuppa joe,” Moum says. “Unfortunately, the coffee will be cold by then. Or, we can introduce some external energy into the system, and mix it.”

A stirring spoon reveals motions in the mug outlined by the black/white contrasts of cream in coffee until the contrast completely disappears, and the color achieves that of café au lait.

“Mixing is obviously important in our normal lives, from the kitchen to the dispersal of pollutants in the atmosphere, reducing them to levels that are barely tolerable,” he said.

The new study shows how mixing, at the same small scales that appear in your morning coffee, is critical to the ocean. It outlines the processes that create the equatorial Pacific cold tongue, a broad expanse of ocean near the equator that is roughly the size of the continental United States, with sea surface temperatures substantially cooler than surrounding areas.

Because this is a huge expanse that takes up heat from the atmosphere, understanding how it does so is critical to seasonal weather patterns, El Nino, and to global climate change.

In temperate latitudes, the atmosphere heats the ocean in summer and cools it in winter. This causes a clear seasonal cycle in sea surface temperature, at least in the middle of the ocean. At low latitudes near the equator, the atmosphere heats the sea surface throughout the year. Yet a strong seasonal cycle in sea surface temperature is present here, as well. This has puzzled oceanographers for decades who have suspected mixing may be the cause but have not been able to prove this.

Moum, Nash and their colleagues began their effort in 2005 to document mixing at various depths on an annual basis, which previously had been a near-impossible task.

“This is a very important area scientifically, but it’s also quite remote,” Moum said. “From a ship it’s impossible to get the kinds of record lengths needed to resolve seasonal cycles, let alone processes with longer-term cycles like El Nino and La Nina. But for the first time in 2005, we were able to deploy instrumentation to measure mixing on a NOAA mooring and monitor the processes on a year-round basis.”

The researchers found clear evidence that mixing alone cools the sea surface in the cold tongue, and that the magnitude of mixing is influenced by equatorial currents that flow from east to west at the surface, and from west to east in deeper waters 100 meters beneath the surface.

“There is a hint – although it is too early to tell – that increased mixing may lead, or have a correlation to the development of La Niña,” Moum said. “Conversely, less mixing may be associated with El Niño. But we only have a six-year record – we’ll need 25 years or more to reach any conclusions on this question.”

Nash said the biggest uncertainty in climate change models is understanding some of the basic processes for the mixing of deep-ocean and surface waters and the impacts on sea surface temperatures. This work should make climate models more accurate in the future.

The research was funded by the National Science Foundation, and deployments have been supported by the National Oceanic and Atmospheric Administration. Continued research will add instruments at the same equatorial mooring and an additional three locations in the equatorial Pacific cold tongue to gather further data.

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Jim Moum, 541-737-2553

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Buoy at sea

OSU geographer to receive international prize for mediation

CORVALLIS, Ore. – An Oregon State University faculty member has won a major international prize for his mediation efforts in water conflicts.

Aaron Wolf, a geography professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences, has been named a 2013 recipient of Il Monito del Giardino (The Warning from the Garden) Award by the Bardini and Peyron Monumental Parks Foundation of Florence, Italy.

The honor is given to persons who have distinguished themselves internationally in safeguarding the environment and raising awareness of ecological issues. The 2012 recipient was Jane Goodall.

Wolf will receive his award next week June in Florence.

The scientific committee cited Wolf’s involvement in striving for more democratic access to the world’s water sources. “The value of his work has come to be recognized on the world stage, mediation work in controversies relative to water’s being at the center of the geopolitical scences that are very delicate, such as that of the Mideast.”

Wolf has traveled throughout the world as both a scientist and a mediator in the area of water conflicts. He has been a consultant to the U.S. Department of State, the U.S. Agency for International Development, the World Bank, and numerous governments.

He directs the Program in Water Conflict Management and Transformation, and developed the Transboundary Freshwater Dispute database, which includes a compilation of 400 water-related treaties as well as information on water conflicts and resolution.

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Aaron Wolf, 541-737-2722; wolf@geo.oregonstate.edu

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Natural Resources Leadership Academy 2012
Aaron Wolf

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About Oregon State University: OSU is one of only two U.S. universities designated a land-, sea-, space- and sun-grant institution. OSU is also Oregon’s only university to hold both the Carnegie Foundation’s top designation for research institutions and its prestigious Community Engagement classification. Its more than 26,000 students come from all 50 states and more than 90 nations. OSU programs touch every county within Oregon, and its faculty teach and conduct research on issues of national and global importance.

Antarctic salty soil sucks water out of atmosphere: Could it happen on Mars?

CORVALLIS, Ore. – The frigid McMurdo Dry Valleys in Antarctica are a cold, polar desert, yet the sandy soils there are frequently dotted with moist patches in the spring despite a lack of snowmelt and no possibility of rain.

A new study, led by an Oregon State University geologist, has found that that the salty soils in the region actually suck moisture out of the atmosphere, raising the possibility that such a process could take place on Mars or on other planets.

The study, which was supported by the National Science Foundation, has been published online this week in the journal Geophysical Research Letters, and will appear in a forthcoming printed edition.

Joseph Levy, a post-doctoral researcher in OSU’s College of Earth, Ocean, and Atmospheric Sciences, said it takes a combination of the right kinds of salts and sufficient humidity to make the process work. But those ingredients are present on Mars and, in fact, in many desert areas on Earth, he pointed out.

“The soils in the area have a fair amount of salt from sea spray and from ancient fjords that flooded the region,” said Levy, who earned his doctorate at Brown University. “Salts from snowflakes also settle into the valleys and can form areas of very salty soil. With the right kinds of salts, and enough humidity, those salty soils suck the water right out of the air.

“If you have sodium chloride, or table salt, you may need a day with 75 percent humidity to make it work,” he added. “But if you have calcium chloride, even on a frigid day, you only need a humidity level above 35 percent to trigger the response.”

Once a brine forms by sucking water vapor out of the air, Levy said, the brine will keep collecting water vapor until it equalizes with the atmosphere.

“It’s kind of like a siphon made from salt.”

Levy and his colleagues, from Portland State University and Ohio State University, found that the wet soils created by this phenomenon were 3-5 times more water-rich than surrounding soils – and they were also full of organic matter, including microbes, enhancing the potential for life on Mars. The elevated salt content also depresses the freezing temperature of the groundwater, which continues to draw moisture out of the air when other wet areas in the valleys begin to freeze in the winter.

Though Mars, in general, has lower humidity than most places on Earth, studies have shown that it is sufficient to reach the thresholds that Levy and his colleagues have documented. The salty soils also are present on the Red Planet, which makes the upcoming landing of the Mars Science Laboratory this summer even more tantalizing.

Levy said the science team discovered the process as part of “walking around geology” – a result of observing the mysterious patches of wet soil in Antarctica, and then exploring their causes. Through soil excavations and other studies, they eliminated the possibility of groundwater, snow melt, and glacial runoff. Then they began investigating the salty properties of the soil, and discovered that the McMurdo Dry Valleys weather stations had reported several days of high humidity earlier in the spring, leading them to their discovery of the vapor transfer.

“It seems kind of odd, but it really works,” Levy said. “Before one of our trips, I put a bowl of the dried, salty soil and a jar of water into a sealed Tupperware container and left it on my shelf. When I came back, the water had transferred from the jar to the salt and created brine.

“I knew it would work,” he added with a laugh, “but somehow it still surprised me that it did.”

Evidence of the salty nature of the McMurdo Dry Valleys is everywhere, Levy said. Salts are found in the soils, along seasonal streams, and even under glaciers. Don Juan Pond, the saltiest body of water on Earth, is found in Wright Valley, the valley adjacent to the wet patch study area.

“The conditions for creating this new water source into the permafrost are perfect,” Levy said, “but this isn’t the only place where this could or does happen. It takes an arid region to create the salty soils, and enough humidity to make the transference work, but the rest of it is just physics and chemistry.”

Other authors on the study include Andrew Fountain, Portland State University, and Kathy Welch and W. Berry Lyons, Ohio State University.

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Joe Levy, 541-737-4915

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McMurdo Dry Valleys
Polar desert sucks water from the atmosphere

"Patchiness” altering perceptions of ocean predators, prey

CORVALLIS, Ore. – Scientists and resource managers have always been interested in how animals in the ocean find their prey and the relative health of marine ecosystems is often judged by the abundance of food for the myriad species living there.

But new studies focusing on ocean “patchiness” suggest that it isn’t just the total amount of prey that is important to predators – it is the density of the food source, and ease of access to it.

Kelly Benoit-Bird, an Oregon State University oceanographer, outlined the importance of this new way of looking at ocean habitats during a keynote talk Wednesday (Feb. 22) at the 2012 Ocean Sciences meeting in Salt Lake City, Utah.

Sophisticated new technologies are helping scientists document how predators target prey, from zooplankton feasting on phytoplankton, to dolphins teaming up to devour micronekton, according to Benoit-Bird, who received a prestigious MacArthur Fellowship in 2010.

“We used to think that the size and abundance of prey was what mattered most,” said Benoit-Bird, a marine ecologist who studies relationships among marine species. “But patchiness is ubiquitous in marine systems and ultimately dictates the behavior of many animals and their relationships to the environment. We need to change our way of thinking about how we look at predator-prey relationships.”

Benoit-Bird pointed to a section of the Bering Sea, where her research with collaborators had estimated the abundance of krill. Closer examination through the use of acoustics, however, found that the distribution of krill was not at all uniform – and this may explain why two colonies of fur seals and seabirds were faring poorly, but a third was healthy.

“The amount of food near the third colony was not abundant,” she said, “but what was there was sufficiently dense – and at the right depth – that made it accessible to predators.”

The ability to use acoustics to track animal behavior underwater is opening new avenues to researchers.  During their study in the Bering Sea, Benoit-Bird and her colleagues discovered that they could also use sonar to plot the dives of thick-billed murres, which would plunge up to 200 meters below the surface in search of the krill.

Although the krill were spread throughout the water column, the murres ended up focusing on areas where the patches of krill were the densest.

“The murres are amazingly good at diving right down to the best patches,” Benoit-Bird pointed out. “We don’t know just how they are able to identify them, but 10 years ago, we wouldn’t have known that they had that ability. Now we can use high-frequency sound waves to look at krill, different frequencies to look at murres, and still others to look at squid, dolphins and other animals.

“And everywhere we’ve looked the same pattern occurs,” she added. “It is the distribution of food, not the biomass, which is important.”

An associate professor in the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University, Benoit-Bird has received young investigator or early career awards from the Office of Naval Research, the White House and the American Geophysical Union. She also has received honors from the Acoustical Society of America, which has used her as a model scientist in publications aimed at middle school students.

Her work has taken her around the world, including Hawaii where she has used acoustics to study the sophisticated feeding behavior of spinner dolphins. Those studies, she says, helped lead to new revelations about the importance of patchiness.

Ocean physics in the region results in long, thin layers of phytoplankton that may stretch for miles, but are only a few inches thick and a few meters below the surface. Benoit-Bird and her colleagues discovered a layer of zooplankton – tiny animals that feed on the plankton – treading water a meter below to be near the food source. Next up in the food chain were micronekton, larger pelagic fish and crustaceans that would spend the day 600 to 1,000 meters beneath the surface, then come up to the continental shelf at night to target the zooplankton. And the spinner dolphins would emerge at night, where they could reach the depth of the micronekton.

“The phytoplankton were responding to ocean physics,” Benoit-Bird said, “but all of the others in the food chain were targeting their prey by focusing on the densest patches. We got to the point where we could predict with 70 percent accuracy where the dolphins would show up based just on the phytoplankton density – without even considering the zooplankton and micronekton distribution.”

Ocean “patchiness” is not a new concept, Benoit-Bird says, but may have been under-appreciated in importance.

“If you’re a murre that is diving a hundred meters below the surface to find food, you want to maximize the payoff for all of the energy you’re expending,” Benoit-Bird said. “Now we need more research to determine how different species are able to determine where the best patches are.”

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Kelly Benoit-Bird, 541-737-2063

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Dolphins circling prey
Dense patches of food draw ocean predators