Air above Dead Sea contains very high levels of oxidized mercury

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Air above Dead

Air above Dead

Measurements show that the sea’s salt has profound effects on the chemistry of the air above its surface. The atmosphere over the Dead Sea, researchers have found, is laden with oxidized mercury. Some of the highest levels of oxidized mercury ever observed outside the polar regions exist there.

The results appear in a paper published on-line November 28th in the journal Nature Geoscience.

In the research, funded by the National Science Foundation (NSF), scientist Daniel Obrist and colleagues at the Desert Research Institute in Reno, Nevada, and at Hebrew University in Isreal measured several periods of extremely high atmospheric oxidized mercury.

Mercury exists in the atmosphere in an elemental and in an oxidized state. It’s emitted by various natural and human processes, and can be converted in the atmosphere between these forms.

High levels of oxidized mercury are a concern, says Obrist, because this form is deposited quickly in the environment after its formation.

Atmospheric mercury deposition is the main way mercury, a potent neurotoxin, finds its way into global ecosystems.

After it’s deposited, mercury can accumulate through the food chain where it may reach very high levels. “These levels are of major concern to humans,” says Obrist, “especially in the consumption of mercury-laden fish.”

Fish caught in oceans are the main source of mercury intake in the U.S. population.

Observations of high naturally-occurring oxidized mercury levels had been limited to the polar atmosphere. There, oxidized mercury is formed during a process called atmospheric mercury depletion events.

During mercury depletions, elemental mercury is converted to oxidized mercury, which is then readily deposited on surfaces.

These events may increase mercury loads to sensitive arctic environments by hundreds of tons of mercury each year.

Now, Obrist says, “we’ve found near-complete depletion of elemental mercury–and formation of some of the highest oxidized mercury levels ever seen–above the Dead Sea, a place where temperatures reach 45 degrees Celsius.”

Such pronounced mercury depletion events were unexpected outside the frigid poles. High temperatures were thought to impede this chemical process.

“Elemental mercury is somewhat resistant to oxidation, so it’s been difficult to explain levels of oxidized mercury measured in the atmosphere outside polar regions,” says Alex Pszenny, director of NSF’s Atmospheric Chemistry Program, which funded the research. “These new results provide an explanation.”

The mechanisms involved in the conversion of mercury above the Dead Sea appear similar, however, to those in polar regions: both start with halogens.

Halogens, or halogen elements, are non-metal elements such as fluorine, chlorine, bromine and iodine.

Observations and modeling results indicate that at the Dead Sea, the conversion of elemental mercury is driven by bromine.

The new results show that bromine levels observed above oceans may be high enough to initiate mercury oxidation.

“We discovered that bromine can oxidize mercury in the mid-latitude atmosphere,” says Obrist, “far from the poles. That points to an important role of bromine-induced mercury oxidation in mercury deposition over the world’s oceans.”

What goes into the ocean, he says, may eventually wind up in its fish. And in those who eat them.

Research highlights the ‘human face’ of climate change

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Research-highlights

Research-highlights

Five years of social science research in Canada’s arctic has taught one University of Guelph geography professor a thing or two about climate change’s “human face.” Barry Smit is the Canada Research Chair in Global Environmental Change, and since 2005 he’s studied how Arctic communities have tried to adapt to the rising temperatures caused by major shifts in global weather patterns.

The human dimension of climate change has long been understudied, says Smit, who is taking part this week in a panel discussion on the environment and economy at the first ever Canada Research Chairs conference in Toronto.

Over the course of two research projects – one with ArcticNet and another with the International Polar Year project – Smit has seen first-hand how Canada’s Inuit have dealt with changing ice levels, wind speed, migration routes, and so on.

“It’s already affecting the people who live there,” says Smit about the impact of global warming.

“And they’re having to figure out ways of adapting their livelihoods to face the changes caused by these changing conditions.”

Some communities are seeing their dietary patterns evolve because the animals they’ve traditionally hunted have shifted their migratory patterns, says Smit. That shift has caused those communities to rely on grocery stores for their food – and since the groceries found in Canada’s arctic are often no better than “what we in the south would generally characterize as junk food,” that’s led to teeth problems and higher rates of diabetes, says Smit.

Part of the goal of his research, says Smit, is to challenge the idea that physical and social environments are completely unrelated. That’s certainly not true, he says, if you look at how many Inuit relate to the ice they live on.

“The ice is their highway. And one of the thing they’ve noticed is that their highway is collapsing in places its never collapsed before,” he says.

Smit’s work has involved partnerships not only with researchers from other Arctic countries but also stakeholders in the communities themselves. His team’s research, he says, has been incorporated into the communities’ day-to-day decision-making – in the setting of hunting quotas, for instance, or in the construction of buildings on the melting permafrost.

And he points out that the research isn’t just a one-way exchange, one where his team bestows its wisdom upon the Arctic communities. Instead, the Inuit communities have helped refine his own research – by pointing out, for example, that it’s not so much the warmer temperatures that create the most significant social problems, but the changing winds that move the ice to places it’s never been before.

Smit has also been involved with similar research into the relationship between social and environmental outcomes in Chile and Ghana. He adds that he’s working on a co-operative project with researchers and community members in the South Pacific and on Haida Gwaii off the coast of British Columbia to study the social impact of rising ocean levels.

All that work, he says, is concerned with bringing about a more “holistic analysis” of climate change.

“The human face of climate change isn’t often recognized,” he says.

Location, location, location: Some coral reefs less vulnerable to rising sea temperatures

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Some-coral-reefs-less

Some-coral-reefs-less

New research highlighting coastal locations where coral can better withstand rising sea temperatures, a leading cause of stress to coral reefs, may guide efforts to conserve the largest living structures on Earth. The findings hold promise for an estimated 100 million people living along the coasts of tropical developing countries whose livelihoods and welfare depend directly on coral reefs, but are currently under threat from climate change.

In a report published in an online edition of Ecology Letters today, scientists from Australia, the UK, Mexico and the US, mapped coral stress across the Bahamas in the Caribbean and found that sea temperatures, which strongly influence coral health, caused less stress to reefs in certain areas.

This discovery was borne out in the second half of the study, during which the researchers designed marine reserves best-suited to four possible scenarios of how coral would respond to further sea temperature rises. In each hypothetical scenario, 15 per cent of the locations in the Bahamas were consistently selected.

While the study’s lead author, Professor Peter J. Mumby, from the Global Change Institute and the ARC Centre of Excellence for Coral Reef Studies says the research complicates current understanding of marine reserve design, the findings can help make the best use of the limited resources available for coral reef conservation.

“Designing marine reserves for the long-term is more difficult than we thought”, Prof. Mumby says. “The responses of coral to the impacts of climate change are relatively unknown at this stage. Yet the good news is that some geographic locations were consistently selected in the generated scenarios, regardless of how corals might adapt to warmer temperatures.

“These areas are great contenders for early conservation no matter what the future holds”. Prof Mumby adds that, “The research found good locations for protecting corals and we are providing this information to conservation partners in the Bahamas to help them in their efforts to work with local communities and establish new reserves.”

Prof. Mumby says the response of coral to climate change is an ongoing focus for scientists and conservation advice will be updated regularly to reflect new research findings.

Prof. Mumby says the world’s oceans are becoming warmer due to the increasing concentration of atmospheric carbon dioxide produced by the burning of fossil fuels. A rise in sea temperature by as little as 1°C causes stress to corals and can lead to coral bleaching, where corals lose their internal symbiotic algae that help them grow, and may result in vast areas of dead coral.

Scientists expect that warming sea temperatures could cause coral to die in large numbers. The destruction of coral reef ecosystems will expose people in coastal areas of developing countries to flooding, coastal erosion and the loss of food and income from reef-based fisheries and tourism.

Can cacti ‘escape’ underground in high temperatures?

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Underground in high

Underground in high

“One crucial point is that small desert plants such as the ‘living rock’ cactus occupy one of the hottest habitats on earth, the surface of desert soils” stated North.

Ariocarpus fissuratus earned its nickname “living rock” because it blends into the rocky surroundings with its small stature that is level with the soil’s surface. The researchers hypothesized that the cactus could “escape” high temperatures by moving more of itself below the soil surface where it is cooler.

Measuring changes in plant depth and root anatomy, North and co-workers determined that the cactus moves deeper into the soil by contracting its roots. But does root contraction play a protective role by modulating temperatures?

To find out, the researchers mimicked summer desert conditions by growing plants on a rooftop in Los Angeles, where air temperature was above 99°F for several days. All the cacti were grown in sandy soil, but half had rocks covering the surface of the soil, similar to their native habitats. For plants grown in rocky soils, the internal temperature of the stem was about 39°F lower than those grown in sandy soils alone. While this may seem like a small decrease, it had a significant effect on the health of the plants.

Unlike the cacti grown in sandy soil which all died, those grown in rocky soil survived the intense heat. Root contraction aided in lowering the internal stem temperature, but only when combined with the cooling effects of the rocky surface. The opposite was true in sandy soil where cacti planted higher above the surface had slightly lower stem temperatures than those planted close to the surface.

“Even in rocky soil, experimental plants attained nearly lethal temperatures during a summer heat wave in Los Angeles” said North. “Thus, root contraction and rocky microhabitats may not provide enough protection should desert temperatures get much higher due to global warming.

Scientists question fisheries health test

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Fisheries-health

Fisheries-health

A measure widely advocated as a means of assessing the health of marine ecosystems is an ineffective guide to trends in biodiversity, and more direct monitoring is needed, a new study has found. The findings – published this week in Nature – followed an examination of whether changes in fishery catches reflect changes in the structure of marine food webs, and therefore are a suitable guide to assess the impacts of fishing on marine ecosystem health. CSIRO Wealth from Oceans Flagship scientist, Dr Beth Fulton, and Dr Sean Tracey from the Tasmanian Aquaculture and Fisheries Institute at the University of Tasmania, were members of the international team involved in the study.

“Biodiversity indicators are used to track the impacts of fishing as a guide to management effectiveness,” Dr Fulton said.

“The most widely adopted indicator of biodiversity in the ocean at a global scale is the ‘average trophic level’ (position in the food chain) determined from fishery catches.

“This is intended to detect shifts from high-trophic-level predators such as Atlantic cod and tunas to low-trophic-level fish, invertebrates and plankton-feeders such as oysters.” Dr Tracey said the study was the first large-scale test of whether average trophic level determined by fishery catch is a good indicator of ecosystem average trophic level, marine biodiversity and ecosystem status.

“We looked at average trophic level determined from a range of sources including global fishery catches, long-term surveys, stock assessments and complex computer modelling for marine ecosystems around the world,” Dr Tracey said.

“In contrast to previous findings, which reported declines in catch average trophic level thought to be due to the loss of large fish and the increasing catch of small fish, we found that catches are increasing at most levels of marine food webs and that the average trophic level has actually increased in the past 25 years.

“We also found that average trophic level determined from fishery catches does not reliably measure the magnitude of fishing impacts or the rate at which marine ecosystems are being altered by fishing.”

Dr Tracey says global fisheries are at a crucial turning point, with high fishing pressure being offset in some regions by rebuilding efforts. Relying on the average trophic level of catch could mislead policy development.

Dr Fulton said that, to target limited resources in the best way, researchers should focus on assessing species vulnerable to fishing that are not currently assessed effectively

“We also need to develop and expan trend-detection methods that can be applied more widely, particularly to countries with few resources for science and assessment.

“Through such efforts we can better detect and convey the true impact of fisheries on marine biodiversity,” Dr Fulton said.

Led by University of Washington fisheries scientist, Trevor A. Branch, the study’s findings are published in a letter in Nature entitled: “The trophic fingerprint of marine fisheries”.

Biologists report more bad news for polar bears

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Biologists-report-more-bad

Biologists-report-more-bad

Will polar bears survive in a warmer world? UCLA life scientists present new evidence that their numbers are likely to dwindle. As polar bears lose habitat due to global warming, these biologists say, they will be forced southward in search of alternative sources of food, where they will increasingly come into competition with grizzly bears.

To test how this competition might unfold, the UCLA biologists constructed three-dimensional computer models of the skulls of polar bears and grizzly bears  a subspecies of brown bears and simulated the process of biting. The models enabled them to compare the two species in terms of how hard they can bite and how strong their skulls are.

“What we found was striking,” said Graham Slater, a National Science Foundation–funded UCLA postdoctoral scholar in ecology and evolutionary biology and lead author of the research. “The polar bear and brown bear can bite equally hard, but the polar bear’s skull is a much weaker structure.”

The implication is that polar bears are likely to lose out in competition for food to grizzlies as warmer temperatures bring them into the same environments, because grizzlies’ stronger skulls are better suited to a plant-rich diet, said Slater and Blaire Van Valkenburgh, UCLA professor of ecology and evolutionary biology and senior author of the research.

“The result for polar bears may be lower weight, smaller and fewer litters, less reproductive success, fewer that would survive to adulthood, and dwindling populations,” Van Valkenburgh said. “Then you can get into an extinction vortex, where a small population becomes even smaller in a downward spiral to extinction.

“To people who say polar bears can just change their diet, we are saying they will change their diet — they will have to — but it probably will not be sufficient for them, especially if they are co-existing with grizzly bears. Their skull is relatively weak and not suited to adapting its diet. We did not expect to find what we found.”

“This is one additional piece of evidence that things look pretty bleak for the polar bear if current trends continue,” Slater said.

The research, federally funded by the National Science Foundation, was published this month in the online journal PLoS ONE, a publication of the Public Library of Science.

Polar bears are a “marvelous example of rapid adaptation to an extreme environment,” Slater said. “The fact that we can lose them equally as rapidly as a result of human-mediated climate change is rather striking. Polar bears are very well suited to do what they do, but they are highly specialized and not well suited to doing much else.”

It could take quite some time for polar bears to go extinct, Van Valkenburgh said, but they are likely to become much more rare than today.

Polar bears are losing habitat as a result of global warming and the associated loss of arctic sea ice, which they use to hunt for seals, Van Valkenburgh and Slater said. But could they survive on an alternative food source?

“Our results suggest that this is not too likely,” Slater said. “The polar bear’s skull is a relatively weak structure that is not suited to diets consisting of a lot of plant material like that of the brown bear. As climate change continues, polar bears will be forced to move south in search of resources, while brown bears move north as their climate becomes more mild. When these two species meet, as they have already begun to, it seems that brown bears will easily out-compete polar bears. Our findings should serve as a warning that polar bears may not be flexible enough to survive if current trends continue.

“Chewing a lot of vegetables takes quite a lot of force to grind up,” Slater said. “Grizzly bears are well suited to eating these kinds of food, but the polar bear is not well suited for it. The grizzly has a much more efficient skull for eating these kinds of foods.”

In Canada, grizzly bears are moving north and are already in polar bear territory, Van Valkenburgh and Slater said.

The life scientists — whose co-authors include UCLA undergraduates Leeann Louis and Paul Yang and graduate student Borja Figueirido from Spain’s Universidad de Malaga, Campus Universitario de Teatinos — studied two adult male skulls from museums, one of a polar bear from Canada, the other of a grizzly from Alaska. They built 3-D computer models of the skulls and then analyzed their biomechanics.

“We can apply muscle forces to the skull to simulate biting, and we can measure how hard the animal could bite. We can measure stress and strain in the skull as well,” Slater said. “We found that while the stresses in the grizzly bear skull are relatively low, the same bites in the polar bear produce much more stress. Combined with other evidence from Blaire’s laboratory, this tells us that the smaller teeth of polar bears are less suited to diets that consist of plants, grass, vegetation and berries.”

“Polar bears would not be able to break up the food as well in their mouths and would not digest it as well,” Van Valkenburgh said.

In the timeline of evolution, polar bears evolved from the brown bear very recently, and the two are very closely related, Van Valkenburgh and Slater said. Genetic studies indicate that the split between polar bears and brown bears occurred only 500,000 to 800,000 years ago — the most recent split between any of the eight bear species.

Despite the recentness of the split between these two species, their skulls and teeth are extremely different, probably as a result of where they live (arctic versus temperate regions) and the differences in their diets. Grizzly bears have very large molar teeth, while polar bears have teeth that are much smaller. Polar bears eat seal blubber, which is soft and does not require much chewing, while brown bears consume many plants.

The biologists investigated the rate at which skull shape has evolved in the bear family. They found that the rate of evolution in the branch of the bear family tree leading to the polar bear was twice as fast as the rates in other branches of the tree; it appears that skull shape evolved extremely rapidly in polar bears.

Polar bears probably evolved very rapidly in response to glacial climates during the ice ages, Slater said.

“You don’t see many bears that look like polar bears, and the difference in skull shape evolved very rapidly,” Slater said.

Shrubby crops can help fuel Africa’s green revolution

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Shrubby crops can help fuel

Shrubby crops can help fuel

Crop diversification with shrubby legumes mixed with soybean and peanuts could be the key to sustaining the green revolution in Africa, according to a Michigan State University study. The study, which appears in the Nov. 22 issue of the Proceedings of the National Academy of Sciences, states that diversifying crops would boost production of nutrient-enriched grain by 12 percent to 23 percent, said Sieglinde Snapp, a crop and soil scientist at Michigan State University’s Kellogg Biological Station.

Malawi has been called the cradle of Africa’s green revolution. Through its government subsidizing 90 percent of fertilizer and superior corn seed costs, Malawi has reaped substantial gains in productivity of calorie-rich food. The successful program has had some unintended consequences, though, such as reliance on starchy cereals, expensive fertilizer and depleted soils.

Rotating corn with pigeonpea mixtures (a shrubby legume grown in tropical regions) keeps the soil from being stripped of nutrients while increasing nutrient-rich grain productivity. This sustained boost would enhance food and environmental security in Africa, Snapp said.

“This diversified rotation provides multiple benefits compared to simply planting a continuous corn crop,” she said. “One big plus is that it will allow twice as much sunlight capture and nitrogen fixation, which supplements fertilizer and improves the efficiency of any fertilizer that is applied. This translates to more stable grain production and enhanced nutritional grain.”

The nation furthered its green reputation by committing at every level to make this unprecedented long-term and wide-ranging study possible. It was carried out over multiple years and involved thousands of extension educators, farmers, government officials, hospital staff, university educators and farmer research groups, according to Snapp.

“This participatory research approach has led to an agricultural revolution, one that will provide multiple benefits other than increased productivity,” she said. “For example, as dependency on fertilizer and subsidies decrease, the government can use the money to invest in education, health and civil society.”

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