Striking Ecological Impact on Canada's Arctic Coastline Linked to Global Climate Change

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Scientists from Queen's and Carleton universities head a national multidisciplinary research team that has uncovered startling new evidence of the destructive impact of global climate change on North America's largest Arctic delta.

"One of the most ominous threats of global warming today is from rising sea levels, which can cause marine waters to inundate the land," says the team's co-leader, Queen's graduate student Joshua Thienpont. "The threat is especially acute in polar regions, where shrinking sea ice increases the risk of storm surges."

By studying growth rings from coastal shrubs and lake sediments in the Mackenzie Delta region of the Northwest Territories -- the scene of a widespread and ecologically destructive storm surge in 1999 -- the researchers have discovered that the impact of these salt-water surges is unprecedented in the 1,000-year history of the lake.

"This had been predicted by all the models and now we have empirical evidence," says team co-leader Michael Pisaric, a geography professor at Carleton. The Inuvialuit, who live in the northwest Arctic, identified that a major surge had occurred in 1999, and assisted with field work.

The researchers studied the impact of salt water flooding on alder bushes along the coastline. More than half of the shrubs sampled were dead within a year of the 1999 surge, while an additional 37 per cent died within five years. A decade after the flood, the soils still contained high concentrations of salt. In addition, sediment core profiles from inland lakes revealed dramatic changes in the aquatic life -- with a striking shift from fresh to salt-water species following the storm surge.

"Our findings show this is ecologically unprecedented over the last millennium," says Queen's biology professor and team member John Smol, Canada Research Chair in Environmental Change and winner of the 2004 NSERC Herzberg Gold Medal as Canada's top scientist. "The Arctic is on the front line of climate change. It's a bellwether of things to come: what affects the Arctic eventually will affect us all."

Since nearly all Arctic indigenous communities are coastal, the damage from future surges could also have significant social impacts. The team predicts that sea ice cover, sea levels and the frequency and intensity of storms and marine storm surges will become more variable in the 21st century.

Other members of the team include Trevor Lantz from the University of Victoria, Steven Kokelj from Indian and Northern Affairs Canada, Steven Solomon from the Geological Survey of Canada and Queen's undergraduate student Holly Nesbitt. Their findings are published in the Proceedings of the National Academy of Sciences.

Research funding comes from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Polar Continental Shelf Program, the Cumulative Impact Monitoring Program, and Indian and Northern Affairs Canada.

Gut Bacteria Linked to Behavior: That Anxiety May Be in Your Gut, Not in Your Head

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For the first time, researchers at McMaster University have conclusive evidence that bacteria residing in the gut influence brain chemistry and behaviour.

The findings are important because several common types of gastrointestinal disease, including irritable bowel syndrome, are frequently associated with anxiety or depression. In addition there has been speculation that some psychiatric disorders, such as late onset autism, may be associated with an abnormal bacterial content in the gut.

"The exciting results provide stimulus for further investigating a microbial component to the causation of behavioural illnesses," said Stephen Collins, professor of medicine and associate dean research, Michael G. DeGroote School of Medicine. Collins and Premysl Bercik, assistant professor of medicine, undertook the research in the Farncombe Family Digestive Health Research Institute.

The research appears in the online edition of the journal Gastroenterology.

For each person, the gut is home to about 1,000 trillium bacteria with which we live in harmony. These bacteria perform a number of functions vital to health: They harvest energy from the diet, protect against infections and provide nutrition to cells in the gut. Any disruption can result in life-threatening conditions, such as antibiotic-induced colitis from infection with the "superbug" Clostridium difficile.

Working with healthy adult mice, the researchers showed that disrupting the normal bacterial content of the gut with antibiotics produced changes in behaviour; the mice became less cautious or anxious. This change was accompanied by an increase in brain derived neurotrophic factor (BDNF), which has been linked, to depression and anxiety.

When oral antibiotics were discontinued, bacteria in the gut returned to normal. "This was accompanied by restoration of normal behaviour and brain chemistry," Collins said.

To confirm that bacteria can influence behaviour, the researchers colonized germ-free mice with bacteria taken from mice with a different behavioural pattern. They found that when germ-free mice with a genetic background associated with passive behaviour were colonized with bacteria from mice with higher exploratory behaviour, they became more active and daring. Similarly, normally active mice became more passive after receiving bacteria from mice whose genetic background is associated with passive behaviour.

While previous research has focused on the role bacteria play in brain development early in life, Collins said this latest research indicates that while many factors determine behaviour, the nature and stability of bacteria in the gut appear to influence behaviour and any disruption , from antibiotics or infection, might produce changes in behaviour. Bercik said that these results lay the foundation for investigating the therapeutic potential of probiotic bacteria and their products in the treatment of behavioural disorders, particularly those associated with gastrointestinal conditions such as irritable bowel syndrome.

The research was funded by grants from the Canadian Institutes of Health Research (CIHR) and the Crohn's and Colitis Foundation of Canada (CCFC).

Zebrafish Regrow Fins Using Multiple Cell Types, Not Identical Stem Cells

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What does it take to regenerate a limb? Biologists have long thought that organ regeneration in animals like zebrafish and salamanders involved stem cells that can generate any tissue in the body. But new research suggests that multiple cell types are needed to regrow the complete organ, at least in zebrafish.

Researchers at Washington University School of Medicine in St. Louis have shown that cells capable of regenerating a zebrafish fin do not revert to stem cells that can form any tissue. Instead, the individual cells retain their original identities and only give rise to more of their own kind.

The findings support a recent shift in how biologists understand organ regeneration in organisms such as salamanders and zebrafish. Understanding regeneration in model organisms gives hope that it may one day be possible for amputees to regrow limbs or for heart attack patients to regrow healthy heart muscle.

"Limb regeneration has long captured people's imaginations," says Stephen L. Johnson, PhD, associate professor of genetics at the School of Medicine. "Traditionally, when people have looked at how a limb regenerates, they see a group of cells forming at the amputation site and the cells all look the same. So they've imagined that these cells have lost their identities and can become anything else. Our results show that this is not the case in the zebrafish fin. And there is mounting evidence that this is not the case in the salamander limb."

The study appears online May 16 in Developmental Cell.

When a zebrafish loses its fin, a special group of cells forms on the remaining stump. These cells, which appear identical to one another, regrow the entire limb, complete with all cell types required for a complex organ. This has suggested that these cells may be "pluripotent" stem cells, capable of forming almost every tissue in the body.

To determine if this was indeed the case, Johnson and postdoctoral research associate Shu Tu, PhD, who did this work for her doctoral thesis, used genetic techniques to label individual cells in the stump with a fragment of DNA that makes the cells glow green.

When a cell divides, it copies its DNA so that each daughter cell has a complete set of genetic material. Since Johnson and Tu's label is inserted into the cell's DNA, the cells also duplicate the label and pass it on to each daughter cell. By simply observing which cells glow green, Johnson and Tu could track the subsequent daughter cells and determine what cell types they become.

For example, they saw that when they had glowing skin cells in the stump, only skin cells glowed in the regenerated limb. Likewise, when a nerve cell glowed in the stump, only nerve cells glowed in the regenerated limb. In other words, they saw no evidence that a skin cell glowing in the stump could give rise to a nerve cell glowing later in the fin's development or regeneration.

Using this technique, Johnson and Tu identified nine separate cell lineages present at the end of the stump that contribute to forming the fin's skin, nerves, pigment, blood vessels, bone and immune cells.

Johnson points out possible implications for future regenerative medicine in humans.

"This is evidence that we can't necessarily do regenerative medicine by plopping in generalized stem cells," he says. "The key may be to induce the cells that are already there to grow again. We need to understand and account for every cell lineage and then convince them to play ball together."

Liquid water possible on Earthlike planet, plus black-hole atoms, Io’s magma ocean

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Titan’s liquid-water ocean
Known for its hydrocarbon lakes and methane-rich atmosphere, Saturn’s moon Titan may contain a water ocean beneath its icy shell, a new study suggests. The moon’s orbit, rotation and related properties can best be explained if Titan isn’t solid throughout but harbors a subsurface ocean of water, researchers from the Royal Observatory of Belgium in Brussels report in an upcoming Astronomy & Astrophysics. —Ron Cowen


Io’s magma ocean runs deep
A new study ends any doubt that Jupiter’s moon Io, the solar system’s most volcanically active body, has an internal ocean of magma. The study also reveals that the ocean must be more than 50 kilometers deep, researchers report online May 12 in Science. Krishan Khurana of UCLA and his collaborators base their findings on a reanalysis of data recorded by NASA’s Galileo spacecraft. —Ron Cowen


Black-hole atoms
Instead of evaporating, mini–black holes created during the Big Bang may survive and trap nearby particles into stable orbits, forming the gravitational equivalent of atoms. These survivors could contribute to the dark matter that makes up most of the cosmos’ mass. Such atomlike systems on or near Earth weighing at least 1,000 tons may be detected through emissions produced when the trapped matter falls from a higher to a lower energy state, just as electrons orbiting atoms do. Researchers from Sandia National Laboratories in Albuquerque and Halcyon Molecular in Redwood City, Calif., describe their idea in a paper posted May 3 at arXiv.org. If such systems exist, they would shed light on black hole evaporation and quantum gravity. —Ron Cowen


’SuperEarth’ may have liquid water
Gliese 581d may be the first planet only a few times heavier than Earth that is known to reside in its star’s habitable zone, the region where water would remain liquid on the body’s surface. A team of French scientists came to that conclusion after detailed climate simulations of the planet, dubbed a superEarth because it weighs about 5.6 times Earth’s mass. Because of its relatively large distance from the star Gliese 581, the planet — one of six orbiting the star — had been thought too cold to have liquid water on its surface. But the new model says otherwise, the team reports in an upcoming Astrophysical Journal

Daytime bites for zombie ants

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Final death grip for the living dead of the insect world comes at midday

Zombie time in Thai forests turns out to be brunch time.

Ants fatally infected with a fungus that turns them into staggering weirdos were most likely to stumble around from about 9:30 a.m. until noon or 1 p.m., says evolutionary biologist David Hughes of Pennsylvania State University in University Park.

The approach of noon in the forest brought a spike in what may be the ants’ most peculiar behavior, Hughes and his colleagues report online May 9 in BMC Ecology. Afflicted Camponotus leonardi ants bite into the vein of a leaf about 2.5 meters off the ground and stay clamped there even after death. Out of 16 ants observed at their last chomp, nine bit the leaf between 11:30 a.m. and noon. All the observed final bites, for unknown reasons, occurred between 11 a.m. and 1:45 p.m. Actual death, not easy to determine with zombies, occurred some hours later, possibly near sunset.

Researchers also got into the heads of the zombies. Dissections suggest Ophiocordyceps fungal buildup may explain the infected ants’ erratic gait and convulsions, which probably keep zombies from climbing back into the canopy where they normally live. And muscle atrophy, possibly from rapid post-bite fungal growth, may keep the ants from pulling their mouthparts loose from fibrous leaf tissue once they’ve bitten in.

Death grips on low leaves give the fungus auspicious humidity to reproduce far from the sun-scorched forest canopy, Hughes has reported. Yet the notion that any parasite is manipulating its host is tricky to prove. “One of the alternative hypotheses in these cases is that the change in behavior is a side effect of infection, not something the fungus ‘actively' does to the host,” says behavioral physiologist Shelley Adamo of Dalhousie University in Halifax, Canada. So far though, she says, the zombie-maker fungus “fits most of the criteria for parasitic manipulation.”

This ant, turned into a kind of zombie by a fatal fungus infection, has taken its final death-grip bite into a leaf vein and merely twitches slightly instead of attacking when an interloper scurries over.

Microbial mats may have given early animals breathing room

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Canadian ponds and Venezuelan lagoons inspire a hypothesis about ancient life.

Like exhausted nightclubbers, early animals may have weathered their harsh lifestyle by squirming up to the oxygen bar.

Animals living more than 550 million years ago could have survived inhospitable oceans by associating with dense mounds of cyanobacteria called microbial mats, an international team of researchers argues in a new study. Such clumps of oxygen-producing gunk could have supplied the first mobile animals with food to eat and air to breathe, the group reports online May 15 in Nature Geoscience.

The animal kingdom’s vanguard would have needed all the help it could get. Recent fossil finds show that wriggling animals first emerged at least 555 million years ago, when atmospheric oxygen concentrations may have been about one-tenth what they are today. Yet as creatures moved around more, they needed more oxygen. So how early mobile critters, which probably resembled worms or slugs, eked out a living in these choked environments has been a big puzzle for paleontologists, says study coauthor Murray Gingras. "Biomats provided the oxygen that ironically enabled the animals to better exploit biomats as food," he says.

He got his first clue after drilling into a frozen pond in Alberta, Canada. The pond, almost entirely deprived of oxygen, hosted a small number of insect larvae surrounding a layer of photosynthesizing algae. “They were eating the biological material, and they were using it as a scuba tank at the same time,” says Gingras, a paleontologist at the University of Alberta in Edmonton.

Alberta’s frozen lakes don’t look much like ancient oceans, however, so Gingras and his colleagues turned to supersalty lagoons in Venezuela. Here, gelatinous masses of cyanobacteria, a type of oxygen-producing microbes with ancient origins, clog the waters. Animals first evolved in a similar “world ruled by microorganisms,” Gingras says, in which microbial mats like these may have dominated shallow oceans across the globe. In fact, he adds, the oldest discovered fossil trace of animal life depicts the tooth marks of a long-dead creature biting into such a mound of bacteria.

The modern lagoons, like their ancient counterparts, carry few traces of oxygen. But the gas does run high — reaching near or above typical water levels — right above and below the mats, the team discovered. These lagoons usually host scant animal life but, as in Alberta, clusters of insect larvae gather around the mats, taking bites and maybe breaths. The first mobile animals easily could have done the same, Gingras says.

“In a way, it’s dead obvious,” says Mary Droser, a paleontologist at the University of California, Riverside.

But ancestral animals didn’t necessarily need scuba gear, suggests Donald Canfield, a geobiologist at the University of Southern Denmark in Odense. Ancient critters may not have had the same insatiable need for air that most modern animals do, he explains. Even today, marine worms and other animals flourish in deep ocean habitats where oxygen is thin. Exploring how these worms survive, Canfield adds, may give scientists insight into how the first creatures with wanderlust grabbed a foothold in an unwelcoming world.

Melting icebergs fertilize ocean

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Release of extra iron boosts carbon dioxide uptake by plankton

Efforts to remove climate-warming carbon dioxide from Earth’s atmosphere appear to be getting a helping hand from a surprising source: the iron in meltwater from Antarctic icebergs.

Icebergs calving off of Antarctica are shedding substantial iron — the equivalent of a growth-boosting vitamin — into waters starved of the mineral, a new set of studies demonstrates. This iron is fertilizing the growth of microscopic plants and algae, transforming the waters adjacent to ice floes into teeming communities of everything from tiny shrimplike krill to fish, birds and sometimes mammals.

To grow, these plants and animals use carbon drawn into the water from carbon dioxide in the atmosphere. Some share of this carbon will eventually be excreted as wastes that fall to the ocean floor, essentially removing it as a near-term climate risk.

“Icebergs should be considered by climate modelers, because the more icebergs that develop [from the breakup of glaciers], the more carbon dioxide you’ll draw out of the atmosphere,” says Ken Smith of the Monterey Bay Aquarium Research Institute in Moss Landing, Calif.

Smith and colleagues first fingered icebergs as hotspots of biological and chemical activity in a 2007 study published in Science. New data from Antarctic cruises in 2008 and 2009 by Smith and other scientists from nine research institutions now appear as 20 papers in the June Deep Sea Research Part II.

Researchers refer to icebergs’ carbon removal as an export. “And the amount of carbon being exported near icebergs is twice as high as in areas away from them,” Smith says.

Counterbalancing icebergs’ carbon removal: No one views the sea-level rise accompanying massive ice melting as a good thing. The rate of iceberg calving — and ice loss — in recent years has increased there, as elsewhere, in response to warming of Earth’s atmosphere.

Prior to the new studies, “we didn’t know the nature of the biological communities associated with icebergs and we certainly didn’t know their direct relationship to carbon exports,” says chemist Timothy Shaw of the University of South Carolina in Columbia, who coauthored several of the new reports.

One surprise: The proliferation of phytoplankton — tiny plants at the base of the marine food chain — that were witnessed in the waters around ice floes “could only account for about half of the increased carbon export we measured,” Shaw says. His team now attributes the other half to changes in the chemistry of iron and carbon use by phytoplankton living next to and under the icebergs.

Benjamin Twining of the Bigelow Laboratory for Ocean Sciences in West Boothbay Harbor, Maine, points to another big surprise: Icebergs’ iron enrichment of southern waters could vary by a factor of 100 from one iceberg to another, or even along walls of a given berg. This patchy enrichment reflects differences in chemical reactions triggered by various organisms and to the unexpectedly complicated turbulence associated with water melting from the floes.

How leeches are able to swell tenfold, plus not-so-super solids, new natural toxins and more

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Not so super after all?
A team of researchers is challenging the claim that scientists have spotted a new state of matter. First reported in 2004, “supersolidity” would occur in solid helium at extremely low temperatures, allowing atoms to slide through one another (SN: 9/11/10, p. 22). In the May 13 Science, Séamus Davis of Cornell and his colleagues report new work on frozen helium. They say they see a bizarre type of crystallization that could explain the helium’s behavior without invoking supersolidity. —Alexandra Witze


Garden-variety poisons
Move over Monsanto, Bayer and Syngenta. A new study finds that some plants produce chemicals that “are as toxic as commonly used herbicides and biocides.” Scandinavian researchers acquired cyclotides, unusual circular poisons made by coffee plants, violets and members of the melon family (to name a few), and applied them to everything from lettuce and algae to soil bacteria. The particular compounds the researchers selected — typical of cyclotides produced by the African plant Oldenlandia affinis and the English violet — “were toxic to all test organisms,” the scientists report in the May Environmental Toxicology and Chemistry. These data point to plants that could harm nearby crops by releasing the compounds into soil. —Janet Raloff


Quick infection test
Researchers are closer to a quick and easy test for bacterial urinary tract infections. Standard techniques for detecting UTIs, the second most common infection in the U.S., involve growing collected bacteria in a dish, which can take up to three days. Now, using a bit of E. coli genetic material as a self-seeking flashlight, Stanford researchers detected the bacterium’s genetic material in urine samples and quantified the infection load in less than 15 minutes. The researchers would like to make the test even more sensitive and tune it to other kinds of bacteria, but preliminary work, to appear in Analytical Chemistry, suggests rapid diagnostic tests aren’t far off. —Rachel Ehrenberg


Bloodsucker’s body booster
The multitasking compound that plays a role in depression, milk production, bone health and digestion also helps bloodsucking leeches swell to more than 10 times their size when eating. Serotonin seems to make muscles of the medicinal leech, Hirudo verbena, resistant to overstretching, while also boosting contractibility, scientists from Wellesley College in Massachusetts have discovered. But there isn’t much potential for human therapies — with or without serotonin, leech muscles are arranged differently than those of animals with bones, aiding in leeches’ remarkable enlargement, the team notes in the May 11

Earthquake risk in Chile, plus an ancient Greek island and casino pollution in this week’s news

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Andes quake risk
People living on the west side of the Andes generally expect large earthquakes, like the magnitude-8.8 quake that struck last year off the coast of Chile. But those farther inland are also at risk, a new study suggests. Global-positioning data show that the ground east of the central Andes, such as in eastern Bolivia, moves far less than the west and hence might be building up stress. Earthquakes as large as magnitude 8.7 to 8.9 — not 7.5, as previously thought — could thus strike where 2 million people live. Researchers led by Benjamin Brooks of the University of Hawaii at Manoa report the finding online May 8 in Nature Geoscience. —Alexandra Witze


Athens’ ancient island
Take a cruise to Greece and you’ll likely dock at Piraeus, which is now a peninsula but was once an island, new research suggests. In the first century, the Greek historian Strabo wrote that the Athenian port was once surrounded by water, and now French and Greek geologists have discovered he was right. By scrutinizing sediments drilled nearby, the scientists found that rising sea levels cut off Piraeus from the mainland between 4850 and 3450 B.C. and again between 2850 and 1550 B.C. The work appeared online May 4 in Geology. —Alexandra Witze


Gambling with the heart and lungs
Breathing is a risky bet in casinos that allow smoking. A team of researchers compared air pollution inside 66 casinos that allowed smoking with that in three casinos that imposed a smoking ban. In smoke-free casinos, the air was no more polluted than outdoors — typically about 3 to 4 micrograms of fine particulates per cubic meter of air. In smoking casinos, secondhand smoke boosted particulate pollution counts to 50 micrograms per cubic meter; one establishment had four times that much. Smoky air in roughly half of the casinos “exceeded a level known to produce cardiovascular morbidity in nonsmokers after less than two hours ... posing acute health risks,” the scientists report in the May Environmental Research. —Janet Raloff


Early dioxin exposure impairs sperm quality
Exposure to relatively low levels of dioxins in the womb and during infancy can induce developmental changes in boys that will permanently diminish sperm quality, a new study finds. An international team of researchers studied 97 young Italian men, including 39 whose mothers had been exposed to a major industrial release of dioxins in 1976. Sperm quality was comparable among all of the men — except those whose moms had lived near the dioxin accident and breastfed their babies. That exposed group of men have half the normal sperm count and a 20 percent reduction in sperm motility, the scientists report in the May

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