OREGON STATE UNIVERSITY

college of science

Breakthrough in study of aluminum should yield new technological advances

CORVALLIS, Ore. – Researchers at Oregon State University and the University of Oregon today announced a scientific advance that has eluded researchers for more than 100 years – a platform to study and fully understand the aqueous chemistry of aluminum, one of the world’s most important metals.

The findings, reported in Proceedings of the National Academy of Sciences, should open the door to significant advances in electronics and many other fields, ranging from manufacturing to construction, agriculture and drinking water treatment.

Aluminum, in solution with water, affects the biosphere, hydrosphere, geosphere and anthrosphere, the scientists said in their report. It may be second only to iron in its importance to human civilization. But for a century or more, and despite the multitude of products based on it, there has been no effective way to explore the enormous variety and complexity of compounds that aluminum forms in water.

Now there is.

“This integrated platform to study aqueous aluminum is a major scientific advance,” said Douglas Keszler, a distinguished professor of chemistry in the OSU College of Science, and director of the Center for Sustainable Materials Chemistry.

“Research that can be done with the new platform should have important technological implications,” Keszler said. “Now we can understand aqueous aluminum clusters, see what’s there, how the atomic structure is arranged.”

Chong Fang, an assistant professor of chemistry in the OSU College of Science, called the platform “a powerful new toolset.” It’s a way to synthesize aqueous aluminum clusters in a controlled way; analyze them with new laser techniques; and use computational chemistry to interpret the results. It’s simple and easy to use, and may be expanded to do research on other metal atoms.

“A diverse team of scientists came together to solve an important problem and open new research opportunities,” said Paul Cheong, also an OSU assistant professor of chemistry.

The fundamental importance of aluminum to life and modern civilization helps explain the significance of the advance, researchers say. It’s the most abundant metal in the Earth’s crust, but almost never is found in its natural state. The deposition and migration of aluminum as a mineral ore is controlled by its aqueous chemistry. It’s found in all drinking water and used worldwide for water treatment. Aqueous aluminum plays significant roles in soil chemistry and plant growth.

Aluminum is ubiquitous in cooking, eating utensils, food packaging, construction, and the automotive and aircraft industries. It’s almost 100 percent recyclable, but in commercial use is a fairly modern metal. Before electrolytic processes were developed in the late 1800s to produce it inexpensively, it was once as costly as silver.

Now, aluminum is increasingly important in electronics, particularly as a “green” component that’s cheap, widely available and environmentally benign.

Besides developing the new platform, this study also discovered one behavior for aluminum in water that had not been previously observed. This is a “flat cluster” of one form of aluminum oxide that’s relevant to large scale productions of thin films and nanoparticles, and may find applications in transistors, solar energy cells, corrosion protection, catalytic converters and other uses.

Ultimately, researchers say they expect new technologies, “green” products, lowered equipment costs, and aluminum applications that work better, cost less and have high performance.

The research was made possible, in part, by collaboration between chemists at OSU and the University of Oregon, through the Center for Sustainable Materials Chemistry. This is a collaboration of six research universities, which is sponsored and funded by the National Science Foundation.

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Aluminum in manufacturing

Aluminum manufacturing

Increasing toxicity of algal blooms tied to nutrient enrichment and climate change

CORVALLIS, Ore. – Nutrient enrichment and climate change are posing yet another concern of growing importance – an apparent increase in the toxicity of some algal blooms in freshwater lakes and estuaries around the world, which threatens aquatic organisms, ecosystem health and human drinking water safety.

As this nutrient enrichment, or “eutrophication” increases, so will the proportion of toxin-producing strains of cyanobacteria in harmful algal blooms, scientists said.

Researchers from Oregon State University and the University of North Carolina at Chapel Hill will outline recent findings in an analysis Friday in the journal Science.

Cyanobacteria are some of the oldest microorganisms on Earth, dating back about 3.5 billion years to a time when the planet was void of oxygen and barren of most life. These bacteria are believed to have produced the oxygen that paved the way for terrestrial life to evolve. They are highly adaptive and persistent, researchers say, and today are once again adapting to new conditions in a way that threatens some of the life they originally made possible.

A particular concern is Microcystis sp., a near-ubiquitous cyanobacterium that thrives in warm, nutrient-rich and stagnant waters around the world. Like many cyanobacteria, it can regulate its position in the water column, and often forms green, paint-like scums near the surface.

In a high-light, oxidizing environment, microcystin-producing cyanobacteria have a survival advantage over other forms of cyanobacteria that are not toxic. Over time, they can displace the nontoxic strains, resulting in blooms that are increasingly toxic.

“Cyanobacteria are basically the cockroaches of the aquatic world,” said Timothy Otten, a postdoctoral scholar in the OSU College of Science and College of Agricultural Sciences, whose work has been supported by the National Science Foundation. “They're the uninvited guest that just won't leave.”

“When one considers their evolutionary history and the fact that they've persisted even through ice ages and asteroid strikes, it's not surprising they're extremely difficult to remove once they’ve taken hold in a lake,” he said. “For the most part, the best we can do is to try to minimize the conditions that favor their proliferation.”

Researchers lack an extensive historical record of bloom events and their associated toxicities to put current observations into a long-term context.  However, Otten said, “If you go looking for toxin-producing cyanobacteria, chances are you won't have to look very long until you find some.”

There are more than 123,000 lakes greater than 10 acres in size spread across the United States, and based on the last EPA National Lakes Assessment, at least one-third may contain toxin-producing cyanobacteria. Dams; rising temperatures and carbon dioxide concentrations; droughts; and increased runoff of nutrients from urban and agricultural lands are all compounding the problem.

Many large, eutrophic lakes such as Lake Erie are plagued each year by algal blooms so massive that they are visible from outer space. Dogs have died from drinking contaminated water.

Researchers studying cyanobacterial toxins say it’s improbable that their true function was to be toxic, since they actually predate any predators. New research suggests that the potent liver toxin and possible carcinogen, microcystin, has a protective role in cyanobacteria and helps them respond to oxidative stress. This is probably one of the reasons the genes involved in its biosynthesis are so widespread across cyanobacteria and have been retained over millions of years.

Because of their buoyancy and the location of toxins primarily within the cell, exposure risks are greatest near the water's surface, which raises concerns for swimming, boating and other recreational uses.

Also, since cyanobacteria blooms become entrenched and usually occur every summer in impacted systems, chronic exposure to drinking water containing these compounds is an important concern that needs more attention, Otten said.

“Water quality managers have a toolbox of options to mitigate cyanobacteria toxicity issues, assuming they are aware of the problem and compelled to act,” Otten said. “But there are no formal regulations in place on how to respond to bloom events.

“We need to increase public awareness of these issues,” he said. “With a warming climate, rising carbon dioxide levels, dams on many rivers and overloading of nutrients into our waterways, the magnitude and duration of toxic cyanobacterial blooms is only going to get worse.”

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Green wake


Toxic bacteria

Toxic bacteria


Lake sample

Toxic algal bloom

Beyond antibiotics: “PPMOs” offer new approach to bacterial infection

CORVALLIS, Ore. – Researchers at Oregon State University and other institutions today announced the successful use of a new type of antibacterial agent called a PPMO, which appears to function as well or better than an antibiotic, but may be more precise and also solve problems with antibiotic resistance.

In animal studies, one form of PPMO showed significant control of two strains of Acinetobacter, a group of bacteria of global concern that has caused significant mortality among military personnel serving in Middle East combat.

The new PPMOs offer a fundamentally different attack on bacterial infection, researchers say.

They specifically target the underlying genes of a bacterium, whereas conventional antibiotics just disrupt its cellular function and often have broader, unwanted impacts. As they are further developed, PPMOs should offer a completely different and more precise approach to managing bacterial infection, or conceptually almost any disease that has an underlying genetic component.

The findings were published today in the Journal of Infectious Diseases, by researchers from OSU, the University of Texas Southwestern Medical Center, and Sarepta, Inc., a Corvallis, Ore., firm.

“The mechanism that PPMOs use to kill bacteria is revolutionary,” said Bruce Geller, a professor of microbiology in the OSU College of Science and lead author on the study. “They can be synthesized to target almost any gene, and in that way avoid the development of antibiotic resistance and the negative impacts sometimes associated with broad-spectrum antibiotics.

“Molecular medicine,” Geller said, “is the way of the future.”

PPMO stands for a peptide-conjugated phosphorodiamidate morpholino oligomer – a synthetic analog of DNA or RNA that has the ability to silence the expression of specific genes. Compared to conventional antibiotics, which are often found in nature, PPMOs are completely synthesized in the laboratory with a specific genetic target in mind.

In animal laboratory tests against A. baumannii, one of the most dangerous Acinetobacter strains, PPMOs were far more powerful than some conventional antibiotics like ampicillin, and comparable to the strongest antibiotics available today. They were also effective in cases where the bacteria were resistant to antibiotics.

PPMOs have not yet been tested in humans. However, their basic chemical structure, the PMO, has been extensively tested in humans and found safe. Although the addition of the peptide to the PPMO poses an uncertain risk of toxicity, the potency of PPMOs reduces the risk while greatly improving delivery of the PMOs into bacterial cells, Geller said.

Geller said research is being done with Acinetobacter in part because this pathogen has become a huge global problem, and is often spread in hospitals. It can cause respiratory infection, sepsis, and is a special concern to anyone whose immune system is compromised. Wounds in military battle conditions have led to numerous cases in veterans, and A. baumannii is now resistant to many antibiotics. “Urgent new approaches to therapeutics are needed,” the scientists said in their report.

Continued research and eventually human clinical trials will be required before the new compounds are available for health care, the researchers said. This and continued studies have been supported by the National Institutes of Health, the other collaborators and the N.L. Tartar fund.

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Editor’s Note: A scanning electron microscope image of A. baumannii is available online (please provide image credit as indicated at web site): http://bit.ly/GztejR

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Red grapes, blueberries may enhance immune function

CORVALLIS, Ore. – In an analysis of 446 compounds for their the ability to boost the innate immune system in humans, researchers in the Linus Pauling Institute at Oregon State University discovered just two that stood out from the crowd – the resveratrol found in red grapes and a compound called pterostilbene from blueberries.

Both of these compounds, which are called stilbenoids, worked in synergy with vitamin D and had a significant impact in raising the expression of the human cathelicidin antimicrobial peptide, or CAMP gene, that is involved in immune function.

The findings were made in laboratory cell cultures and do not prove that similar results would occur as a result of dietary intake, the scientists said, but do add more interest to the potential of some foods to improve the immune response.

The research was published today in Molecular Nutrition and Food Research, in studies supported by the National Institutes of Health.

“Out of a study of hundreds of compounds, just these two popped right out,” said Adrian Gombart, an LPI principal investigator and associate professor in the OSU College of Science. “Their synergy with vitamin D to increase CAMP gene expression was significant and intriguing. It’s a pretty interesting interaction.”

Resveratrol has been the subject of dozens of studies for a range of possible benefits, from improving cardiovascular health to fighting cancer and reducing inflammation. This research is the first to show a clear synergy with vitamin D that increased CAMP expression by several times, scientists said.

The CAMP gene itself is also the subject of much study, as it has been shown to play a key role in the “innate” immune system, or the body’s first line of defense and ability to combat bacterial infection. The innate immune response is especially important as many antibiotics increasingly lose their effectiveness.

A strong link has been established between adequate vitamin D levels and the function of the CAMP gene, and the new research suggests that certain other compounds may play a role as well.

Stilbenoids are compounds produced by plants to fight infections, and in human biology appear to affect some of the signaling pathways that allow vitamin D to do its job, researchers said. It appears that combining these compounds with vitamin D has considerably more biological impact than any of them would separately.

Continued research could lead to a better understanding of how diet and nutrition affect immune function, and possibly lead to the development of therapeutically useful natural compounds that could boost the innate immune response, the researchers said in their report.

Despite the interest in compounds such as resveratrol and pterostilbene, their bioavailability remains a question, the researchers said. Some applications that may evolve could be with topical use to improve barrier defense in wounds or infections, they said.

The regulation of the CAMP gene by vitamin D was discovered by Gombart, and researchers are still learning more about how it and other compounds affect immune function. The unique biological pathways involved are found in only two groups of animals – humans and non-human primates. Their importance in the immune response could be one reason those pathways have survived through millions of years of separate evolution of these species.

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Adrian Gombart, 541-737-8018

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Blueberries

Blueberries


Grapes

Red grapes

Viruses associated with coral epidemic of “white plague”

CORVALLIS, Ore. – They call it the “white plague,” and like its black counterpart from the Middle Ages, it conjures up visions of catastrophic death, with a cause that was at first uncertain even as it led to widespread destruction – on marine corals in the Caribbean Sea.

Now one of the possible causes of this growing disease epidemic has been identified – a group of viruses that are known as small, circular, single-strand DNA (or SCSD) viruses. Researchers in the College of Science at Oregon State University say these SCSD viruses are associated with a dramatic increase in the white plague that has erupted in recent decades.

Prior to this, it had been believed that the white plague was caused primarily by bacterial pathogens. Researchers are anxious to learn more about this disease and possible ways to prevent it, because its impact on coral reef health has exploded.

“Twenty years ago you had to look pretty hard to find any occurrences of this disease, and now it’s everywhere,” said Nitzan Soffer, a doctoral student in the Department of Microbiology at OSU and lead author on a new study just published in the International Society for Microbial Ecology. “It moves fast and can wipe out a small coral colony in a few days.

“In recent years the white plague has killed 70-80 percent of some coral reefs,” Soffer said. “There are 20 or more unknown pathogens that affect corals and in the past we’ve too-often overlooked the role of viruses, which sometimes can spread very fast.”

This is one of the first studies to show viral association with a severe disease epidemic, scientists said. It was supported by the National Science Foundation.

Marine wildlife diseases are increasing in prevalence, the researchers pointed out. Reports of non-bleaching coral disease have increased more than 50 times since 1965, and are contributing to declines in coral abundance and cover.

White plague is one of the worst. It causes rapid tissue loss, affects many species of coral, and can cause partial or total colony mortality. Some, but not all types are associated with bacteria. Now it appears that viruses also play a role. Corals with white plague disease have higher viral diversity than their healthy counterparts, the study concluded.

Increasing temperatures that stress corals and make them more vulnerable may be part of the equation, because the disease often appears to be at its worst by the end of summer. Overfishing that allows more algae to grow on corals may help spread pathogens, researchers said, as can pollution caused by sewage outflows in some marine habitats.

Viral infection, by itself, does not necessarily cause major problems, the researchers noted. Many healthy corals are infected with herpes-like viruses that are persistent but not fatal, as in many other vertebrate hosts, including humans.

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Coral with white plague


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Taking samples

Keszler named associate dean in OSU College of Science

CORVALLIS, Ore. - The College of Science at Oregon State University has named Douglas Keszler as associate dean for research and graduate studies.

Keszler, a distinguished professor in the OSU Department of Chemistry and director of the Center for Sustainable Materials Chemistry, earned his doctorate from Northwestern University and in 1984 joined OSU.

He is an expert on the synthesis and study of inorganic molecules and materials that will enable next-generation electronic and energy devices, including high-efficiency solar cells. His pioneering science contributions are being commercialized by three start-up companies – Inpria, Amorphyx, and Beet.

“I am confident that Doug will have a tremendous impact on the college’s research excellence, collaborations across departments and colleges, mentorship of faculty, industry partnerships and start-ups,” said Sastry G. Pantula, dean of the college, “while increasing the quality, quantity, and diversity of our graduate programs.”

The associate dean supports graduate and faculty research, cultivates collaborative research and large-scale interdisciplinary projects, and helps to identify potential industry partners and start-ups.

 “I look forward to enhancing a supportive and creative research environment, advancing high-quality graduate programs that support broad professional development of students, and enriching the scientific research community at OSU,” Keszler said.

Home to the life, statistical, physical and mathematical sciences, the College of Science has graduated more than 25,000 students since 1932 and is recognized for excellence in research and scholarship.

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Debbie Farris, 541-737-4862

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Doug Keszler

Doug Keszler

Noted researcher to speak at OSU commencement in June

CORVALLIS, Ore. – Ann A. Kiessling, director of the independent Bedford Stem Cell Research Foundation and a leader in both stem cell research and reproductive biology, will give the commencement address at Oregon State University’s graduation ceremony this spring.

Kiessling also will receive an honorary doctorate from the university at its 145th commencement, which begins at 10:30 a.m. on Saturday, June 14, in Reser Stadium.

“Ann Kiessling is a nationally recognized researcher and pioneer whose work in cutting-edge fields of stem cell research and the HIV virus should make for an enlightening talk for our graduates,” said Oregon State University President Edward J. Ray. “She has had a remarkable career that launched at Oregon State, where she earned her Ph.D.”

Kiessling, who has a doctorate in biochemistry and biophysics from Oregon State, joined the faculty of Harvard University in 1985, specializing in obstetrics, gynecology and reproductive biology, and working in the Department of Surgery. In the early 1990s, she pioneered reproductive options for couples living with the HIV disease and hepatitis C – techniques that led to the successful births of 121 children free of those diseases.

The Bedford Research Foundation was founded in 1996 as a Massachusetts public charity to support research. By the year 2000, the foundation’s research laboratory expanded to include human stem cell research. To date, the foundation has collaborated with more than 60 clinics globally to find treatment for infectious diseases and spinal cord injuries. Foundation officials say their belief is that international scientific collaboration is fundamentally important to rapid biomedical advances.

Kiessling’s book, “Human Embryonic Stem Cells: An Introduction to the Science and Therapeutic Potential,” published in 2003 and re-released in 2006, is the first textbook on the topic.

Before joining the Harvard University faculty, Kiessling had a faculty appointment at Oregon Health & Science University, where she worked from 1977-85.

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Sabah Randhawa, 541-737-2111; Sabah.randhawa@oregonstate.edu

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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Silicon nanostructure

Silicon nanostructures


Table salt

Table salt

Lionfish expedition: down deep is where the big, scary ones live

CORVALLIS, Ore. – Last month, the first expedition to use a deep-diving submersible to study the Atlantic Ocean lionfish invasion found something very disturbing – at 300 feet deep, there were still significant populations of these predatory fish, and they were big.

Big fish in many species can reproduce much more efficiently than their younger, smaller counterparts, and lionfish are known to travel considerable distances and move to various depths. This raises significant new concerns in the effort to control this invasive species that is devastating native fish populations on the Atlantic Coast and in the Caribbean Sea.

“We expected some populations of lionfish at that depth, but their numbers and size were a surprise,” said Stephanie Green, the David H. Smith Conservation Research Fellow in the College of Science at Oregon State University, who participated in the dives. OSU has been one of the early leaders in the study of the lionfish invasion.

“This was kind of an ‘Ah hah!’ moment,” she said. “It was immediately clear that this is a new frontier in the lionfish crisis, and that something is going to have to be done about it. Seeing it up-close really brought home the nature of the problem.”

OSU participated in this expedition with researchers from a number of other universities, in work supported by Nova Southeastern University, the Guy Harvey Foundation, NOAA, and other agencies. The five-person  submersible “Antipodes” was provided by OceanGate, Inc., and it dove about 300 feet deep off the coast of Ft. Lauderdale, Fla., near the “Bill Boyd” cargo ship that was intentionally sunk there in 1986 to create an artificial reef for marine life.

That ship has, in fact, attracted a great deal of marine life, and now, a great number of lionfish. And for that species, they are growing to an unusually large size – as much as 16 inches.

Lionfish are a predatory fish that’s native to the Pacific Ocean and were accidentally introduced to Atlantic Ocean waters in the early 1990s, and there became a voracious predator with no natural controls on its population. An OSU study in 2008 showed that lionfish in the Atlantic have been known to reduce native fish populations by up to 80 percent.

Eradication appears impossible, and they threaten everything from coral reef ecosystems to local economies that are based on fishing and tourism.

Whatever is keeping them in check in the Pacific – and researchers around the world are trying to find out what that is – is missing here. In the Caribbean, they are found at different depths, in various terrain, are largely ignored by other local predators and parasites, and are rapidly eating their way through entire ecosystems. They will attack many other species and appear to eat constantly.

And, unfortunately, the big fish just discovered at greater depths pose that much more of a predatory threat, not to mention appetite.

“A lionfish will eat almost any fish smaller than it is,” Green said. “Regarding the large fish we observed in the submersible dives, a real concern is that they could migrate to shallower depths as well and eat many of the fish there. And the control measures we’re using at shallower depths – catch them and let people eat them – are not as practical at great depth.”

Size does more than just increase predation.  In many fish species, a large, mature adult can produce far more offspring that small, younger fish. A large, mature female in some species can produce up to 10 times as many offspring as a fish that’s able to reproduce, but half the size.

Trapping is a possibility for removing fish at greater depth, Green said, and could be especially effective if a method were developed to selectively trap lionfish and not other species. Work on control technologies and cost effectiveness of various approaches will continue at OSU, she said.

When attacking another fish, a lionfish uses its large, fan-like fins to herd smaller fish into a corner and then swallow them in a rapid strike. Because of their natural defense mechanisms they are afraid of almost no other marine life, and will consume dozens of species of the tropical fish and invertebrates that typically congregate in coral reefs and other areas. The venom released by their sharp spines can cause extremely painful stings to humans.

Aside from the rapid and immediate mortality of marine life, the loss of herbivorous fish will also set the stage for seaweed to potentially overwhelm the coral reefs and disrupt the delicate ecological balance in which they exist.

This newest threat follows on the heels of overfishing, sediment deposition, nitrate pollution in some areas, coral bleaching caused by global warming, and increasing ocean acidity caused by carbon emissions. Lionfish may be the final straw that breaks the back of Western Atlantic and Caribbean coral reefs, some researchers believe.

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Submersible research

Submersible in Florida


Exploring sunken ship

Lionfish near sunken ship


Lionfish

Lionfish

Bullfrogs may help spread deadly amphibian fungus, but also die from it

CORVALLIS, Ore. – Amphibian populations are declining worldwide and a major cause is a deadly fungus thought to be spread by bullfrogs, but a two-year study shows they can also die from this pathogen, contrary to suggestions that bullfrogs are a tolerant carrier host that just spreads the disease.

When researchers raised the frogs from eggs in controlled experimental conditions, they found at least one strain of this pathogen, Batrachochytrium dendrobatidis, also called Bd or a chytrid fungus, can be fatal to year-old juveniles. However, bullfrogs were resistant to one other strain that was tested.

The findings, made by researchers at Oregon State University and the University of Pittsburgh, show that bullfrogs are not the sole culprit in the spread of this deadly fungus, and add further complexity to the question of why amphibians are in such serious jeopardy.

About 40 percent of all amphibian species are declining or are already extinct, researchers say. Various causes are suspected, including this fungus, habitat destruction, climate change, pollution, invasive species, increased UV-B light exposure, and other forces.

“At least so far as the chytrid fungus is involved, bullfrogs may not be the villains they are currently made out to be,” said Stephanie Gervasi, a zoology researcher in the OSU College of Science. “The conventional wisdom is that bullfrogs, as a tolerant host, are what helped spread this fungus all over the world. But we’ve now shown they can die from it just like other amphibians.”

The research suggests that bullfrogs actually are not a very good host for the fungus, which first was identified as a novel disease of amphibians in 1998. So why the fungus has spread so fast, so far, and is causing such mortality rates is still not clear.

“One possibility for the fungal increase is climate change, which can also compromise the immune systems of amphibians,” said Andrew Blaustein, a distinguished professor of zoology at OSU and international leader in the study of amphibian declines. “There are a lot of possible ways the fungus can spread. People can even carry it on their shoes.”

The average infection load of the chytrid fungus in bullfrogs, regardless of the strain, is considerably lower than that of many other amphibian species, researchers have found. Some bullfrogs can reduce and even get rid of infection in their skin over time.

While adult bullfrogs may be carriers of some strains of Bd in some areas, the researchers concluded, different hosts may be as or more important in other locations. International trade of both amphibian and non-amphibian animal species may also drive global pathogen distribution, they said.

The findings of this study were published in EcoHealth, a professional journal.

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Bullfrog

Bullfrog