RESEARCHERS LOOK AT BIOLUMINESCENT CREATURES

FROM:  NATIONAL SCIENCE FOUNDATION
Night lights: The wonders of bioluminescent millipedes
A Virginia Tech researcher discusses bioluminescent millipedes and other glowing creatures

There's something inherently magical, even surreal, about seeing hundreds of glowing millipedes scattered across the ground of a sequoia grove on a moonless night in Sequoia National Park.

Every evening, these creatures--which remain hidden underground during the day--emerge and initiate a chemical reaction to produce a green-blue glow, a process called bioluminescence. The eerie night lights of these millipedes highlight nature’s eccentricities. My observations of this phenomena is a fringe benefit of my research of the millipede species known as Motyxia.

Seeing the light

Motyxia, which are the only known bioluminescent millipedes, are found solely in a small region of the Sierra Nevada mountain range in California. But various types of bioluminescent creatures live throughout the United States. They include:

railroad worms, a beetle that looks similar to a millipede but has a string of lights down each of its sides resembling the lit windows of a passenger train at night,
glowworms with bioluminescent lamps on their heads,
a fly larvae with the bluest bioluminescence in the insect world,
firefly larvae that have two abdominal lamps on their tail,
and even luminescent earthworms.
If you would like to see bioluminescent creatures, visit a moist area, such as a gully or streamside, in a deep dark forest late at night--preferably in the early summer, right after a rain.

When you arrive at your viewing sight, turn off your flashlight and let your eyes adjust to the dark. Within about 15 to 30 minutes, you may begin to discern bioluminescent organisms.

Focus on tiny specks of light, which may be firefly larvae. These organisms may quickly turn off their lights when approached--but then turn them on again. So if you initially see a twinkle, note its position relative to nearby stationary objects so that you may see it light up again.

If you want to light your path as you walk, use red light to maintain your light-adapted vision.

Why the turn on?

When you observe bioluminescence, you may wonder about the purpose of this illuminating phenomenon. My research on Motyxia indicates that "Glow means 'No!'" to predators. That is, Motyxia's glow warns nocturnal predators that these 60-legged creatures are armed and dangerous; any predator that riles a Motyxia risks being squirted by toxins, including hydrogen cyanide, an extremely poisonous gas, which the millipede releases when it feels threatened.

The suggestion that Motyxia's glow wards off marauding nocturnal predators is supported by the fact that Motyxia are blind, so their visual signaling can only be seen by members of other species, such as predators.

My research team and I ran an experiment to test whether Motyxia's coloration warns predators to stay away. Our experiment involved positioning 150 glowing clay millipede models and 150 clay non-glowing millipede models in Motyxia's natural nighttime habitat in California.

The results: Predators attacked a significantly lower percentage of the glowing vs. non-glowing models (18 percent vs. 49 percent.) The relatively greater ability of the glowing millipede models to repel predators supports the "Glow Means No!" idea.

Motyxia's eastern cousins possess bright and conspicuous reds and yellows, apparently also to ward off daytime predators.

Other animals that are toxic, inedible, or otherwise noxious also advertise their danger via warning signals. For example, a rattlesnake uses its rattle and the yellow jacket brandishes yellow and black stripes to advertise its threats.

Toxic animals that show bright, highly conspicuous and sometimes downright garish colors to distinguish themselves thereby help prevent predators from mistaking them for edible prey. Such an error would be costly to both predator and prey.

The conspicuous appearance of toxic animals also helps predators learn to recognize their bright coloration as warnings and remember the unpleasant consequences of ignoring them--e.g. a cyanide-induced fever.

How bioluminescence evolved

How did bioluminescence evolve? This question is another focus of our ongoing research on Motyxia.

By helping to reveal the evolutionary origins of warning colorations--which, by necessity, contribute to some of the most blatant and complex appearances in the living world--we expect to improve our ability to investigate and understand how other complex traits arise in nature.

One possible clue to the origins of bioluminescence is provided by a millipede species known as Motyxia sequoiae, which inhabits habitats that are normally off-limits to other closely related millipedes. These habitats include exposed areas of the forest floor, open mountain meadows and the trunks of oak trees.

So perhaps bioluminescence evolved in Motyxia sequoiae to protect these creatures from predators in particularly vulnerable areas, and thereby enable these millipedes to expand their range to these favorable locations.

But why would Motyxia sequoiae evolve bioluminescence instead of any other defense mechanism, such as camouflage or weapons such as claws or sharp spines?

Have you ever heard the saying that "natural selection...works like a tinkerer"? This is a great way to think about the evolution of warning coloration and other complex biologic features. Tinkerers use what's already available (e.g., odds and ends lying around) to repair machines, appliances and other apparatuses.

A body of research suggests that many species may have similarly acquired bioluminescence by "making do" with, or repurposing, biological equipment they already possessed.

For example, fireflies need an enzyme called luciferase to light up. But the original role of the firefly's luciferase wasn't to help these insects produce light, but instead to help them synthesize fatty acids needed to create brain cells.

The essence of bioluminescence

Despite our growing knowledge, much about Motyxia remains mysterious. For example, how do these blind creatures find mates? What triggers their nightly emergence? With funding from the National Science Foundation, my team is working to answer these and other questions.

This research is part of our larger effort to describe biodiversity and reconstruct the evolutionary histories of arthropods--a group that includes insects, spiders and crustaceans, and accounts for 80 percent of all living species. We contribute our findings to the Tree of Life, which is a worldwide effort to define the evolutionary histories of animals.

Some bright ideas from bioluminescence

In addition to advancing our understanding of the history of life, studies of the bioluminescence of various types of organisms have implications for fields ranging from national defense to medicine.

Here are several examples:

The efficiency of electrical lighting systems, which can be only 10 percent efficient, could be improved by designing them to mimic bioluminescent light, which is 90 percent efficient.

The underbellies of some marine bioluminescent animals blend with background light from the water's surface, and so are camouflaged. The U.S. Navy is studying these phenomena so that it may build similarly camouflaged ships.
Healthy human cells produce ultra-weak amounts of light through a process similar to animal bioluminescence, but cancer cells produce slightly more light. Techniques may ultimately be developed to help locate cancer cells by detecting the greater amounts of light they produce.

A green fluorescent protein identified in a jellyfish species is now widely used in biomedical research as a fluorescent tag to help researchers track specific biological activities, such as the spread of cancer, insulin production and the movement of HIV proteins.

The key enzyme for beetle bioluminescence is a pivotal component of a fast, inexpensive method for sequencing genomes, which in 2008 was used to sequence the full genome of a Neanderthal.

Learn more about Dr. Marek's work at jointedlegs.org

-- Paul Marek, Virginia Tech
Investigators
Paul Marek
Related Institutions/Organizations
Virginia Polytechnic Institute and State University

LOOKING TO CURE ANTIBIOTIC RESISTANCE

FROM:  NATIONAL SCIENCE FOUNDATION
Researcher studies how to prevent antibiotic resistance
Solution could be in bacterial protein called UmuD

The widespread and indiscriminate use of antibiotics has prompted many bacteria to mutate, an adaptation that often renders the drugs useless. The increasing threat of resistance worries infectious disease experts who fear that the era of public health successes brought by the introduction of antibiotics in the 1940s is seriously eroding, or soon even may be at an end.

But what if science could improve existing antibiotics in such a way as to not only destroy bacteria, but prevent them from mutating?

At least one research team, in seeking to better understand bacterial mutation, may provide scientific answers that ultimately could lead to thwarting the organisms' ability to mutate, thus blunting the increasing threat of antibiotic resistance.

"The idea would be a one-two punch," says Penny Beuning, an associate professor of chemistry and chemical biology at Northeastern University's college of science. "We need a good therapeutic target that will both kill the bacteria and prevent mutagenesis."

To be sure, the approach almost certainly is years away. Still, the National Science Foundation (NSF)-funded scientist thinks it may be possible. She and her colleagues are studying an important bacterial protein known as UmuD that regulates mutagenesis and may provide important clues about how to stop the process that eventually results in antimicrobial resistance.

Using the bacterium E. coli as a model, she has learned that UmuD interacts with the machinery that replicates DNA, and, when altered, may provide the switch that triggers mutation. UmuD exists in two forms, a full length version when first expressed, and later, if DNA is damaged, a much shorter form. It is this shorter version that allows bacteria to mutate.

Once there is DNA damage, "there is an SOS response, and the levels of some specific proteins go up," she says. "There is a massive stress response, and UmuD responds by cutting its arms off."

In cells where only the full-length version of the protein is present, the bacteria cannot mutate. "But when it forms its shorter self, the cells are mutable," she says.

The fact that UmuD is not present outside bacteria makes it a viable antibiotic target.

"The hope would be to find something that targets UmuD together with an existing antibiotic to prevent bacteria from mutating and developing a resistance to that particular drug," she says. "Among the things we have been looking at: how does UmuD work, and what controls the cleavage of the arms?"

Beuning is conducting her research under an NSF Faculty Early Career Development (CAREER) grant awarded in 2009 under the American Recovery and Reinvestment Act. The award supports junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of education and research within the context of the mission of their organization. NSF is funding her work with $994,655 over five years.

Beuning specifically is looking at the cleavage process of UmuD using gel electrophoresis, which separates proteins according to size.

"UmuD is a small protein--139 amino acids--which loses 24 amino acids from the arm. So it goes from 139 to 115," she says. "We can observe this difference with electrophoresis, allowing us to determine how different conditions or other proteins might affect UmuD cleavage."

The team is studying different UmuD protein interactions in the lab, using biochemistry to see when and how different proteins bind to one another. Essentially "we light up the proteins and measure how they change when other proteins bind, using a method called FRET, which stands for fluorescence resonance energy transfer," she says.

"This measures energy transfer between two proteins using light emission," she adds. "The proteins have to be close to each other for energy transfer to occur, so it's a way of detecting whether two things bind to each other. People often call the technique a molecular ruler, because it can be used to measure precise distances, but we use it simply to measure proximity."

Using FRET, they discovered that UmuD prevents specific protein interactions in the replication process. That is, it stops or slows down replication by keeping two proteins that need to interact for replication from binding to each other. "Protein-protein interactions are generally hard to target with drugs, but the approach has some potential," she says.

They also use another technique that measures how floppy or flexible proteins are by putting them in heavy water and measuring how much heavier the protein gets as it trades its regular hydrogens with heavy hydrogens from the heavy water. "The floppier parts swap out the hydrogens faster than the less floppy parts," she says.

As part of the grant's education component, she has up to ten undergraduates--as well as local high school students and teachers--working in her research lab. Several students have worked in her lab as part of Northeastern's signature co-op program, in which students work full-time for six months in positions related to their career goals.

Also, she teaches an upper level chemical biology class to undergraduates, and created a lab research project for the students that takes place during half of the semester that actually involves them directly in her mutagenesis research.

"A lot of these students had not yet conducted any research, so they were really motivated by the idea of doing something that someone would use as part of a bigger project," she says. "Particularly at Northeastern, where co-op is such a large part of the culture, it is fun to take advantage of the laboratory as the ultimate in experiential education.”

-- Marlene Cimons, National Science Foundation
Investigators
Penny Beuning
Related Institutions/Organizations

GENE EDITITING AND REGULATION TO IMPROVE IMMUNE SYSTEM

FROM:  NATIONAL SCIENCE FOUNDATION
Rewriting genetic information to prevent disease

Breakthrough Prize winner harnesses CRISPR to improve immune system
For the last few years, scientists have been studying an ancient but only recently understood mechanism of bacterial immunity that has the potential to provide immeasurable benefits to plant and animal health.

The phenomenon known as CRISPR (for Clustered Regularly Interspaced Short Palindromic Repeats) is a natural immune system found in many bacteria with the ability to identify and destroy the genomes of invading viruses and plasmids.

Researchers are trying to harness this system for gene editing and regulation, a process that could transform "the genome of plants or animals in ways that will improve their health, or introduce genetic changes that will resist disease of climate change," says Jennifer Doudna, a Howard Hughes Medical Institute investigator and professor of biochemistry, biophysics and structural biology at the University of California, Berkeley. "The explosion of research using this technique has been amazing."

Doudna, collaborating with Emmanuelle Charpentier of Sweden's Helmholtz Center for Infection Research and Umeå University, identified how the system works and engineered it in new ways that broadened its scope. The two researchers, who described their work in a 2012 paper in the journal Science, developed a technique that enables the rewriting of genetic information and the correction of mutations that otherwise can cause disease, and also can knock out the cell's ability to make harmful proteins, she says.

"Many labs have shown in principle that this can be used to correct such mutations as those that occur in cystic fibrosis, or sickle cell disease," she says. "They are showing it in cell lines and lab animals. We're still some period of time away from using this in humans, but the pace in the field has been truly remarkable, and really exciting to see."

Many bacteria have this CRISPR-based immune system capable of identifying and destroying hostile invaders. Doudna and Charpentier showed that, in doing so, CRISPR produces the protein Cas9, a DNA-cutting enzyme guided by RNA, which relies on two short RNA guide sequences to find foreign DNA, then cleaves, or cuts, the target sequences, thereby muting the genes of the invaders.

Cas9 has evolved to provide protection against viruses that could infect the bacterium, and uses pieces of RNA derived from CRISPRS to direct its activity. The system is specific and efficient enough to stave off viral infections in bacteria.

Doudna and her colleagues programmed the process so that it can be directed by a single short RNA molecule; researchers who use it to edit genomes can customize the RNA so that it sends Cas9 to cleave, like "scissors," at their chosen location in the genome.

"When we figured out how it worked, we realized we could alter the design of RNA and program Cas9 to recognize any DNA sequence," she says. "One can therefore target Cas9 to any region of a genome simply by providing a short guide RNA that can pair with the region of interest. Once targeted, different versions of Cas9 can be used to activate or inhibit genes, as well as make target cuts within the genome. Depending on the experimental design, research can use these latter cuts to either disrupt genes or replace them with newly engineered versions."

Recently Douda and Charpentier and four other scientists received the Breakthrough Prize in life sciences, which honors transformative advances toward understanding living systems and extending human life. The prizes recognize pioneering work in physics, genetics, cosmology, neurology and mathematics, and carry a $3 million award for each researcher. The Breakthrough committee specifically cited Doudna and Charpentier for their advances in understanding the CRISPR mechanism.

Doudna has been the recipient of several National Science Foundation (NSF) grants to support her research in recent years totaling more than $1.5 million. In 2000, she received NSF's prestigious $500,000 Alan T. Waterman Award, which recognizes an outstanding young researcher in any field of science or engineering supported by NSF.

She also was a founder of the Innovative Genomics Initiative, established in 2014 at the Li Ka Shing Center for Genomic Engineering at UC Berkeley. Its goal is to promote and support genome editing research and technology in both academic and commercial research communities.

"We have a team of scientists working with various collaborative partners," she says. "We want to ensure that the technology gets into as many hands as possible, and explore ways to make it even better. We are trying to bring about fundamental change in biological and biomedical research by enabling scientists to read and write in genomes with equal ease. It's a bold new effort that embraces a new era in genomic engineering."

-- Marlene Cimons, National Science Foundation
Investigators
Jennifer Doudna
Related Institutions/Organizations
University of California-Berkeley

MAKING MATERIALS FOR FUTURE ELECTRONICS

FROM:  NATIONAL SCIENCE FOUNDATION 

Materials for the next generation of electronics and photovoltaics

MacArthur Fellow develops new uses for carbon nanotubes

One of the longstanding problems of working with nanomaterials--substances at the molecular and atomic scale--is controlling their size. When their size changes, their properties also change. This suggests that uniform control over size is critical in order to use them reliably as components in electronics.

Put another way, "if you don't control size, you will have inhomogeneity in performance," says Mark Hersam. "You don't want some of your cell phones to work, and others not."

Hersam, a professor of materials science engineering, chemistry and medicine at Northwestern University, has developed a method to separate nanomaterials by size, therefore providing a consistency in properties otherwise not available. Moreover, the solution came straight from the life sciences--biochemistry, in fact.

The technique, known as density gradient ultracentrifugation, is a decades-old process used to separate biomolecules. The National Science Foundation (NSF)-funded scientist theorized correctly that he could adapt it to separate carbon nanotubes, rolled sheets of graphene (a single atomic layer of hexagonally bonded carbon atoms), long recognized for their potential applications in computers and tablets, smart phones and other portable devices, photovoltaics, batteries and bioimaging.

The technique has proved so successful that Hersam and his team now hold two dozen pending or issued patents, and in 2007 established their own company, NanoIntegris, jump-started with a $150,000 NSF small business grant. The company has been able to scale up production by 10,000-fold, and currently has 700 customers in 40 countries.

"We now have the capacity to produce ten times the worldwide demand for this material," Hersam says.

NSF supports Hersam with a $640,000 individual investigator grant awarded in 2010 for five years. Also, he directs Northwestern's Materials Research Science and Engineering Center (MRSEC), which NSF funds, including support for approximately 30 faculty members/researchers.

Hersam also is a recent recipient of one of this year's prestigious MacArthur fellowships, a $625,000 no-strings-attached award, popularly known as a "genius" grant. These go to talented individuals who have shown extraordinary originality and dedication in their fields, and are meant to encourage beneficiaries to freely explore their interests without fear of risk-taking.

"This will allow us to take more risks in our research, since there are no 'milestones' we have to meet," he says, referring to a frequent requirement of many funders. "I also have a strong interest in teaching, so I will use the funds to influence as many students as possible."

The carbon nanotubes separation process, which Hersam developed, begins with a centrifuge tube. Into that, "we load a water based solution and introduce an additive which allows us to tune the buoyant density of the solution itself," he explains.

"What we create is a gradient in the buoyant density of the aqueous solution, with low density at the top and high density at the bottom," he continues. "We then load the carbon nanotubes and put it into the centrifuge, which drives the nanotubes through the gradient. The nanotubes move through the gradient until their density matches that of the gradient. The result is that the nanotubes form separated bands in the centrifuge tube by density. Since the density of the nanotube is a function of its diameter, this method allows separation by diameter."

One property that distinguishes these materials from traditional semiconductors like silicon is that they are mechanically flexible. "Carbon nanotubes are highly resilient," Hersam says. "That allows us to integrate electronics on flexible substrates, like clothing, shoes, and wrist bands for real time monitoring of biomedical diagnostics and athletic performance. These materials have the right combination of properties to realize wearable electronics."

He and his colleagues also are working on energy technologies, such as solar cells and batteries "that can improve efficiency and reduce the cost of solar cells, and increase the capacity and reduce the charging time of batteries," he says. "The resulting batteries and solar cells are also mechanically flexible, and thus can be integrated with flexible electronics."

They likely even will prove waterproof. "It turns out that carbon nanomaterials are hydrophobic, so water will roll right off of them," he says.

Materials at the nanometer scale now "can realize new properties and combinations of properties that are unprecedented," he adds. "This will not only improve current technologies, but enable new technologies in the future."

-- Marlene Cimons, National Science Foundation
Investigators
Mark Hersam
Monica Olvera
Related Institutions/Organizations
Northwestern University

JET PROPULSION LABORATORY USES FUEL CELLS TO INVESTIGATE ORIGINS OF LIFE

FROM:  NASA 

How Did Life Arise? Fuel Cells May Have Answers

How life arose from the toxic and inhospitable environment of our planet billions of years ago remains a deep mystery. Researchers have simulated the conditions of an early Earth in test tubes, even fashioning some of life's basic ingredients. But how those ingredients assembled into living cells, and how life was first able to generate energy, remain unknown.

A new study led by Laurie Barge of NASA's Jet Propulsion Laboratory in Pasadena, Calif., demonstrates a unique way to study the origins of life: fuel cells.
Fuel cells are found in specialized cars, planes and NASA's human spacecraft, such as the now-retired space shuttle. The cells are similar to batteries in generating electricity and power, but they require fuel, such as hydrogen gas. In the new study, the fuel cells are not used for power, but for testing chemical reactions thought to have led to the development of life.

"Something about Earth led to life, and we think one important factor was that the planet provides electrical energy at the seafloor," said Barge. "This energy could have kick-started life -- and could have sustained life after it arose. Now, we have a way of testing different materials and environments that could have helped life arise not just on Earth, but possibly on Mars, Europa and other places in the solar system."

Barge is a member of the JPL Icy Worlds team of the NASA Astrobiology Institute, based at NASA's Ames Research Center in Moffett Field, Calif. The team's paper appears online March 13 in the journal Astrobiology.
One of the basic functions of life as we know it is the ability to store and use energy. In cells, this is a form of metabolism and involves the transfer of electrons from one molecule to another. The process is at work in our own bodies, giving us energy.
Fuel cells are similar to biological cells in that electrons are also transferred to and from molecules. In both cases, this results in electricity and power. In order for a fuel cell to work, it needs fuel, such as hydrogen gas, along with electrodes and catalysts, which help transfer the electrons. Electrons are transferred from an electron donor (such as hydrogen) to an electron acceptor (such as oxygen), resulting in current. In your cells, metal-containing enzymes -- your biological catalysts -- transfer electrons and generate energy for life.

In the team’s experiments, the fuel cell electrodes and catalysts are made of primitive geological material thought to have existed on early Earth. If this material can help transfer electrons, the researchers will observe an electrical current. By testing different types of materials, these fuel cell experiments allow the scientists to narrow in on the chemistry that might have taken place when life first arose on Earth.

"What we are proposing here is to simulate energetic processes, which could bridge the gap between the geological processes of the early Earth and the emergence of biological life on this planet," said Terry Kee from the University of Leeds, England, one of the co-authors of the research paper.

"We're going back in time to test specific minerals such as those containing iron and nickel, which would have been common on the early Earth and could have led to biological metabolism," said Barge.

The researchers also tested material from little lab-grown "chimneys," simulating the huge structures that grow from the hydrothermal vents that line ocean floors. These "chemical gardens" are possible locations for pre-life chemical reactions.
When the team used material from the lab-grown chimneys in the fuel cells, electrical currents were detected. Barge said that this is a preliminary test, showing that the hydrothermal chimneys formed on early Earth can transfer electrons – and therefore, may drive some of the first energetic reactions leading to metabolism.

The experiments also showed that the fuel cells can be used to test other materials from our ancient Earth. And if life did arise on other planets, those conditions can be tested, too.

"We can just swap in an ocean and minerals that might have existed on early Mars," said Barge. "Since fuel cells are modular -- meaning, you can easily replace pieces with other pieces -- we can use these techniques to investigate any planet’s potential to kick-start life."

At JPL, fuel cells are not only for the study of life, but are also being developed for long-term human space travel. Hydrogen fuel cells can produce water, which can be recycled and used as fuel again. Researchers are experimenting with these advanced regenerative fuel cells, which are highly efficient and offer long-lasting power.

Thomas I. Valdez, who is developing regenerative fuel cells at JPL, said, "I think it is great that we can transition techniques used to study reactions in fuel cells to areas such as astrobiology."

Other authors of the paper are: Ivria J. Doloboff, Chung-Kuang Lin, Richard D. Kidd and Isik Kanik of the JPL Icy Worlds team; Joshua M. P. Hampton of the University of Leeds School of Chemistry, Mohammed Ismail and Mohamed Pourkashanian at the University of Leeds Centre for Fluid Dynamics; John Zeytounian of the University of Southern California, Los Angeles; and Marc M. Baum and John A. Moss of the Oak Crest Institute of Science, Pasadena.
JPL is managed by the California Institute of Technology in Pasadena for NASA.

WATERSHEDS AFFECTED BY BARK BEETLES

 

Lodgepole Pines.  Credit:  Widimedia.

FROM: NATIONAL SCIENCE FOUNDATION
Ghosts of Forests Past: Bark Beetles Kill Lodgepole Pines, Affecting Entire Watersheds

In mountains across the Western United States, scientists are racing against time--against a tiny beetle--to save the last lodgepole pines.


Forests are bleeding out from the effects of the beetles, their conifers' needles turning crimson before the trees die.

Now, researchers are also hurrying to preserve the region's water quality, affected by the deaths of the pines.

"When these trees die," says hydrologist Reed Maxwell of the Colorado School of Mines, "the loss of the forest canopy affects hydrology and the cycling of essential nutrients."

Maxwell and other scientists recently published results of their study in the journal Biogeochemistry.

Co-authors, in addition to Maxwell, are Kristin Mikkelson, Lindsay Bearup, John McCray and Jonathan Sharp of the Colorado School of Mines, and John Stednick of Colorado State University. Mikkelson is the paper's first author.


Bark beetle numbers: heating up
"The mountain pine beetle outbreak in Western states has reached epidemic proportions," says Maxwell.

Bark beetles, as they're known, are native to the United States. They're so-named as the beetles reproduce in the inner bark of trees. Some species, such as the mountain pine beetle, attack and kill live trees. Others live in dead, weakened or dying hosts.

Massive outbreaks of mountain pine beetles in western North America since the mid-2000s have felled millions of acres of forests from New Mexico to British Columbia, threatening increases in mudslides and wildfires.

Climate change could be to blame. The beetles' numbers were once kept in check by cold winter temperatures and trees that had plenty of water to use as a defense.

But winters have become warmer, and droughts have left trees water-stressed and less able to withstand an onslaught of winged invaders.

"A small change in temperature leads to a large change in the number of beetles--and now to a large change in water quality," says Tom Torgersen, director of the National Science Foundation's (NSF) Water, Sustainability and Climate (WSC) Program, which funded the research.

WSC is part of NSF's Science, Engineering and Education portfolio of investments.

"Bark beetles have killed 95 percent of mature lodgepole pines," says Maxwell.

Death of a lodgepole pine

But the trees don't die immediately.

When beetles invade, a blue fungus spreads inside a tree's trunk, choking off transpiration and killing the tree in about two years.

The trees turn blood-red, then the ashen gray of death, dropping their needles to the forest floor.

"Some of the most important effects of bark beetles may be changes in the hydrologic cycle," says Maxwell, "via snow accumulation under trees and water transpiration from trees and other plants."

Biogeochemical changes may be even more important, he says, with carbon and nitrogen cycles interrupted.

"We're studying these hydrologic and geochemical processes through a combination of field work, lab research and computer modeling," says Maxwell.


Whither the beetles, so the trees, forests...and waters
Changes in tree canopies affect snowpack development and snowmelt.

For example, a lack of needles on branches lets more snow fall through the canopy--snow that would otherwise be caught on branches. A tree without needles also has less shade beneath it.

The result is a shallower snowpack, earlier snowmelt and less water in spring.

"The real question," Maxwell says, "is how these processes translate from individual trees to hillslopes to large watersheds."

Dead trees don't transpire water. Once a forest has died, this important flow of moisture from the ground to the atmosphere ceases.

That can mean a loss of as much as 60 percent of the water budget, although increases in ground evaporation or transpiration from understory shrubs and bushes may compensate for some of the lack.

"Combined with what's happening to snowpack depth," says Maxwell, "it becomes a complicated relationship that can change the timing and magnitude of spring runoff from snowmelt--and an entire year's water resources."

Tree mortality also appears to affect forest carbon and nitrogen cycles through increases in dissolved organic carbon.

"We've seen changes in drinking water quality in beetle-affected watersheds that are almost certainly related to high dissolved organic carbon levels," says Maxwell.

As Maxwell, Mikkelson, Bearup and colleagues discovered, there's a lag time between beetle infestation and water quality declines, "so tree and forest water transport processes are very likely involved," says Maxwell.


All watersheds great and small
The observations prompted the researchers to study processes at the individual tree and hillslope scale to better understand what's happening in watersheds large and small.

"Watersheds are complex, interrelated systems," says Maxwell, "which makes understanding them more challenging.

"We're developing complex, numerical models of bark beetle-infested watersheds that include our best understanding of how and where water flows. The models are allowing us to isolate individual processes by turning them on and off in 'what-if' scenarios."

Along with on-the-ground observations, he says, "they're showing us more of the complex story of pine beetle effects on Western watersheds.

"We now know that healthy watersheds ultimately depend on healthy forests."

Western streams and rivers soon may be part of dead and dying forests, surrounded only by the ghosts of lodgepole pines past.