Extreme Weather Events Fuel Climate Change

One extreme after another: Long periods of drought, such as that shown here in Greece, have the effect that the ecosystem absorbs considerably less carbon than under normal climate conditions.
© Marcel van Oijen

When the carbon dioxide content of the atmosphere rises, the Earth not only heats up, but extreme weather events, such as lengthy droughts, heat waves, heavy rain and violent storms, may become more frequent. Whether these extreme climate events result in the release of more CO2from terrestrial ecosystems and thus reinforce climate change has been one of the major unanswered questions in climate research. It has now been addressed by an international team of researchers working with Markus Reichstein, Director at the Max Planck Institute for Biogeochemistry in Jena. They have discovered that terrestrial ecosystems absorb approximately 11 billion tons less carbon dioxide every year as the result of the extreme climate events than they could if the events did not occur. That is equivalent to approximately a third of global CO2 emissions per year. 

In 2003, Central and Southern Europe sweltered in a heat wave that set alarm bells ringing for researchers. It was one of the first large-scale extreme weather events which scientists were able to use to document in detail how heat and drought affected the carbon cycle (the exchange of carbon dioxide between the terrestrial ecosystems and the atmosphere). Measurements indicated that the extreme weather events had a much greater impact on the carbon balance than had previously been assumed. It is possible that droughts, heat waves and storms weaken the buffer effect exerted by terrestrial ecosystems on the climate system. In the past 50 years, plants and the soil have absorbed up to 30% of the carbon dioxide that humans have set free, primarily from fossil fuels.

The indications that the part played by extreme weather events in the carbon balance had been underestimated prompted scientists from eight countries to launch the CARBO-Extreme Project. For the first time, the consequences of various extreme climate events on forests, bogs, grass landscapes and arable areas throughout the world underwent systematic scrutiny.

Satellites and recording stations document extreme events

Satellites and recording stations document extreme events

The researchers working with Markus Reichstein took different approaches to their study from the ecosystem perspective. Satellite images from 1982 to 2011 revealed how much light plants in an area absorb so that they can perform photosynthesis. From this, they were able to determine how much biomass the ecosystem in question accumulates during or after an extreme weather event. The researchers also used data from a global network of 500 recording stations, some in operation for more than 15 years, which record carbon dioxide concentrations and air currents in the atmosphere a few meters above ground or in forest canopies. Calculations from these values indicate how much carbon an ecosystem absorbs and releases in the form of carbon dioxide.

The many and varied consequences of extreme weather: droughts, heat waves, storms, heavy rain and extreme frost affect the carbon balance of forests, grasslands and agricultural land in different ways. The arrows pointing upward represent additional carbon dioxide in the atmosphere. The arrows pointing downward indicate that carbon dioxide is removed more slowly from the atmosphere. Orange arrows stand for short-term and purple arrows for long-term effects.

© Nature, issue from 15.8.2013, doi 10.1038/nature12350

The team then fed the various readings into complex computer models to calculate the global effect of extreme weather on the carbon balance. The models showed that the effect is indeed extreme: on average, vegetation absorbs 11 billion fewer tonnes of carbon dioxide than it would in a climate that does not experience extremes. "That is roughly equivalent to the amount of carbon sequestered in terrestrial environments every year," says Markus Reichstein. "It is therefore by no means negligible."

Droughts hit vegetation particularly hard

Droughts, heat waves, storms and heavy rain have not yet become dramatically more frequent and pronounced as a consequence of anthropogenic climate change. However, many climate researchers expect that they will in the future. This would mean more carbon dioxide in the atmosphere as a result of extreme weather conditions.

Periods of extreme drought in particular reduce the amount of carbon absorbed by forests, meadows and agricultural land significantly. "We have found that it is not extremes of heat that cause the most problems for the carbon balance, but drought," explains Markus Reichstein. He and his colleagues expect extreme weather events to have particularly pronounced, varied and long-term effects on forest ecosystems. Drought can not only cause immediate damage to trees; it can also make them less resistant to pests and fire. It is also the case that a forest recovers much more slowly from fire or storm damage than other ecosystems do; indeed, grasslands are completely unaffected by high winds.

The researchers also discovered that serious failures to absorb carbonare distributed according to a so-called power law, like avalanches, earthquakes and other catastrophic events. This means that a few major events dominate the global overall effect, while the more frequent smaller events occurring throughout the world play a much less significant part.

Weather extremes are still very rare, but more research is needed

Drought hits the global ecosystems particularly hard: The map shows the regions where drought (blue), heat (red), both (purple) and other (grey) extreme events prevent plant uptake of carbon dioxide and to what extent. Light colours represent a weak effect, darker colours a strong effect.
© Nature, issue from 15.8.2013, doi 10.1038/nature12350

The researchers are planning more studies to improve their understanding of the consequences of extreme events. For example, they want to investigate the way the different ecosystems respond in laboratory and field experiments. "These experiments have already been carried out, but mostly they only look at extreme events which occur once in a 100 years," explains Michael Bahn, a project partner from the University of Innsbruck. "We should also take account of events which so far have only happened once in 1,000 or even 10,000 years, because they are likely to become much more frequent towards the end of this century." The researchers are also suggesting that, in a drought or a storm, satellites be directed at the area in question as quickly as possible so that the immediate effect can be recorded along with the long-term impact.

The investigations of the current study, however, show that the consequences of weather extremes can be far-reaching. "As extreme climate events reduce the amount of carbon that the terrestrial ecosystems absorb and the carbon dioxide in the atmosphere therefore continues to increase, more extreme weather could result," explains Markus Reichstein. "It would be a self-reinforcing effect."

Source :  Max Planck Institute for Biogeochemistry.
By Science and Universe

The ‘genetics of sand’ may shed new light on evolutionary process over millions of years

This image shows a close-up of planktonic
 foraminifera. (Credit: The University of Southampton)

An evolutionary ecologist at the University of Southampton, is using ‘grains of sand’ to understand more about the process of evolution. 

Dr Thomas Ezard is using the fossils of microscopic aquatic creatures called planktonic foraminifera, often less than a millimetre in size, which can be found in all of the world’s oceans. The remains of their shells now resemble grains of sand to the naked eye and date back hundreds of millions of years.

A new paper by Dr Ezard, published today (9 August 2013) in the journal Methods in Ecology & Evolution, opens the debate on the best way to understand how new species come into existence (speciation). The debate concerns whether fossil records such as those of the planktonic foraminifera, contain useful evidence of speciation over and above the molecular study of evolution. Molecular evolution traditionally uses evidence from species that are alive today to determine what their ancestors may have looked like, whereas this new research promotes the importance of using fossil records in conjunction with the molecular models.

Dr Ezard, from Biological Sciences and the Institute for Life Sciences at Southampton, says: “Because planktonic foraminifera have been around for many millions of years and rocks containing groups of their species can be dated precisely, we can use their fossils to see evidence of how species evolve over time. We can also see how differences between individual members of species develop and, in theory, how a new species comes into existence.

“The controversial hypothesis we test is that the processes leading to a new species coming into existence provoke a short, sharp burst of rapid genetic change. This is controversial because it is very difficult to detect these new species coming into existence accurately without the fossil data; it is more commonly determined from assumptions made from the study of species alive today using molecular evidence.”

In the paper, Dr Ezard and colleagues, Dr Gavin Thomas from the University of Sheffield and Professor Andy Purvis from Imperial College London, highlight the importance of using fossil and molecular evidence to study evolution. Their intention is that the use of both types of data will become widespread in the future study of evolution.

To support his research, Dr Ezard has received an Advanced Fellowship from the Natural Environment Research Council (NERC) to study how variation among individuals generates variation among species. He will conduct this interdisciplinary research in the Centre for Biological Sciences at the University, in close collaboration with researchers from Ocean and Earth Science at the National Oceanography Centre, Southampton.

Watch Dr Thomas Ezard, NERC Advanced Senior Research Fellow, Centre for Biological Sciences

Article Source : University of Southampton.

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How Did Earth's Primitive Chemistry Get Kick Started?

This image from the floor of the Atlantic Ocean shows a collection of limestone towers known as the "Lost City." Alkaline hydrothermal vents of this type are suggested to be the birthplace of the first living organisms on the ancient Earth. Scientists are interested in understanding early life on Earth because if we ever hope to find life on other worlds - especially icy worlds with subsurface oceans such as Jupiter's moon Europa and Saturn's Enceladus - we need to know what chemical signatures to look for.
Image courtesy D. Kelley and M. Elend/University of Washington

How did life on Earth get started? Three new papers co-authored by Mike Russell, a research scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., strengthen the case that Earth's first life began at alkaline hydrothermal vents at the bottom of oceans. Scientists are interested in understanding early life on Earth because if we ever hope to find life on other worlds -- especially icy worlds with subsurface oceans such as Jupiter's moon Europa and Saturn's Enceladus -- we need to know what chemical signatures to look for. 

Two papers published recently in the journal Philosophical Transactions of the Royal Society B provide more detail on the chemical and precursor metabolic reactions that have to take place to pave the pathway for life. Russell and his co-authors describe how the interactions between the earliest oceans and alkaline hydrothermal fluids likely produced acetate (comparable to vinegar). The acetate is a product of methane and hydrogen from the alkaline hydrothermal vents and carbon dioxide dissolved in the surrounding ocean. Once this early chemical pathway was forged, acetate could become the basis of other biological molecules. They also describe how two kinds of "nano-engines" that create organic carbon and polymers -- energy currency of the first cells -- could have been assembled from inorganic minerals. 

A paper published in the journal Biochimica et Biophysica Acta analyzes the structural similarity between the most ancient enzymes of life and minerals precipitated at these alkaline vents, an indication that the first life didn't have to invent its first catalysts and engines. 

"Our work on alkaline hot springs on the ocean floor makes what we believe is the most plausible case for the origin of the life's building blocks and its energy supply," Russell said. "Our hypothesis is testable, has the right assortment of ingredients and obeys the laws of thermodynamics." 

Russell's work was funded by the NASA Astrobiology Institute through the Icy Worlds team based at JPL, a division of the California Institute of Technology, Pasadena. The NASA Astrobiology Institute, based at NASA's Ames Research Center, Moffett Field, Calif., is a partnership among NASA, 15 U.S. teams and 13 international consortia. The Institute is part of NASA's astrobiology program, which supports research into the origin, evolution, distribution and future of life on Earth and the potential for life elsewhere.

Source :  NASA/Jet Propulsion Laboratory.

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Secret of plant geometry revealed

 Researchers at the University of Leeds have discovered how plants set the angles of their branches.

While the other principle features governing the architecture of plants such as the control of the number of branches and positioning around the main shoot are now well understood, scientists have long puzzled over how plants set and maintain the angle of their lateral branches relative to gravity.

The mechanism is fundamental to understanding the shape of the plants around us: explaining how, for instance, a young Lombardy poplar sends its branches up close to the vertical while an oak sapling’s spread is much flatter.

Dr Stefan Kepinski, senior lecturer in the University of Leeds’ Faculty of Biological Sciences and lead author of a paper in the journal Current Biology that gets to the bottom of the mystery, said: “We began working on this after a train commute into Leeds. Looking out of the window, I was struck by the fact that the way we recognise tree and other plant species from a distance is largely informed by the angle at which their branches grow.

“These characteristic angles are all around us and the same thing is happening underground; different varieties within species often have very distinct root-system architectures that are determined mainly by the growth angle of lateral roots,” Kepinski said.

The apparently simple puzzle of how a plant sets and maintains these angles in its architecture is complicated by the fact that the angle of root and shoot branches is not usually set relative to the main root or stem from which they grow but relative to gravity. If a plant is put on its side, these branches will begin a phase of bending growth, known as gravitropism, that reorientates them back toward their original angle of growth relative to gravity.

In the case of the main root or stem, which grows upright, the mechanism is well understood: gravity sensing cells called statocytes detect that the plant has been tilted, prompting an increase in the movement of a growth-regulating hormone called auxin to the lower side of the shoot or root and driving upward growth in the shoot and downward growth in the root. When growing vertically again, the statocytes stop sending more auxin to one side than the other and the bending growth stops.

The conundrum for the researchers was that many of the angles in branch and root architectures are at an angle to gravity, rather than being completely upright. Scientists did not understand how plants were able to set, relative to gravity, the particular non-vertical angle of growth for their branches—known as their “gravitropic set-point angle”—that determines their architecture.

Dr Kepinski said: “We have found that another growth component—the ‘anti-gravitropic offset’—counteracts the normal gravitropic growth in these lateral branches. This offset mechanism sustains growth on the other side of a branch from the gravity-sensitive growth and prevents the branch from being moved beyond a set angle to the vertical. It turns out that this countervailing growth is also driven by auxin, the same hormone that causes gravity responsive growth on the lower side of the branch.”

Branches that are growing close to the vertical have a weak anti-gravitropic offset, while in branches that are growing out at shallow angles away from the vertical the anti-gravitropic offset is relatively strong.

Dr Kepinski added: “You can compare it to the way a tank or paddle steamer is steered. If you want to go one direction, you speed up the track or paddle on the other side. If you want to straighten up, you balance the speeds—or in our case the ‘speed’ of growth on either side of the branch. In a given non-vertical branch, the anti-gravitropic offset is constant, while gravity responsive growth increases in magnitude according to how far the branch is away from the vertical, generating a robust system for maintaining a whole array of branch angles.”

The Leeds team  proved the presence of the offset by using a clinostat, which slowly rotates a plant growing on its side, thereby withdrawing a stable gravity reference and enabling the researchers to monitor the anti-gravitropic offset mechanism working unopposed by a coordinated gravitropic response. Under these conditions they observed that shoot and root branches displayed an outward bending growth, away from the main root and shoot that would normally be masked by the interaction with gravity-sensitive growth.

Dr Kepinski said: “The angle of growth of branches is an exceptionally important adaptation because it determines the plant’s capacity to capture resource above and below ground. Depending on what sort of soil a plant is in, it might be beneficial to be foraging for nutrients in the top soil or to be going deeper. Similarly, in the shoot, a plant might gain an advantage from having more steeply pitched branches to avoid shading from neighbouring plants. Until now, nobody really knew how non-vertical growth angles, referenced to gravity like this, were set and maintained.”

He added: “"These insights are important for breeding and biotechnological approaches to crop improvement because breeders and seed companies want to be able to alter plant architecture to optimise the performance of crops. For example, lateral root growth angle has been shown to be critical for increasing nutrient uptake in both broadleaf and cereal crop species. Our findings provide tools and approaches to help meet these crop improvement challenges."

The team used the flowering plant Arabidopsis thaliana (thale cress), as well as pea, bean and rice plants in their experiments, observing the same results. Kepinski expects the same mechanism to be observed in larger plants and young tree seedlings. In older trees, the mechanisms driving gravity sensitive growth in woody tissues are different to those in non-woody plants. Nevertheless, Kepinski says the same general principles may apply.

Neuroscientists Plant False Memories in Mice: Location Where Brain Stores Memory Traces, Both False and Authentic, Pinpointed

MIT neuroscientists identified the cells
(highlighted in red) where memory traces are stored in the
mouse hippocampus.
(Credit: Steve Ramirez and Xu Liu)

The phenomenon of false memory has been well-documented: In many court cases, defendants have been found guilty based on testimony from witnesses and victims who were sure of their recollections, but DNA evidence later overturned the conviction.

In a step toward understanding how these faulty memories arise, MIT neuroscientists have shown that they can plant false memories in the brains of mice. They also found that many of the neurological traces of these memories are identical in nature to those of authentic memories.

“Whether it’s a false or genuine memory, the brain’s neural mechanism underlying the recall of the memory is the same,” says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience and senior author of a paper describing the findings in the July 25 edition of Science. 

The study also provides further evidence that memories are stored in networks of neurons that form memory traces for each experience we have — a phenomenon that Tonegawa’s lab first demonstrated last year. 

Neuroscientists have long sought the location of these memory traces, also called engrams. In the pair of studies, Tonegawa and colleagues at MIT’s Picower Institute for Learning and Memory showed that they could identify the cells that make up part of an engram for a specific memory and reactivate it using a technology called optogenetics. 

Lead authors of the paper are graduate student Steve Ramirez and research scientist Xu Liu. Other authors are technical assistant Pei-Ann Lin, research scientist Junghyup Suh, and postdocs Michele Pignatelli, Roger Redondo and Tomas Ryan. 

Seeking the engram

Episodic memories — memories of experiences — are made of associations of several elements, including objects, space and time. These associations are encoded by chemical and physical changes in neurons, as well as by modifications to the connections between the neurons.

Where these engrams reside in the brain has been a longstanding question in neuroscience. “Is the information spread out in various parts of the brain, or is there a particular area of the brain in which this type of memory is stored? This has been a very fundamental question,” Tonegawa says.

In the 1940s, Canadian neurosurgeon Wilder Penfield suggested that episodic memories are located in the brain’s temporal lobe. When Penfield electrically stimulated cells in the temporal lobes of patients who were about to undergo surgery to treat epileptic seizures, the patients reported that specific memories popped into mind. Later studies of the amnesiac patient known as “H.M.” confirmed that the temporal lobe, including the area known as the hippocampus, is critical for forming episodic memories. 

However, these studies did not prove that engrams are actually stored in the hippocampus, Tonegawa says. To make that case, scientists needed to show that activating specific groups of hippocampal cells is sufficient to produce and recall memories.

To achieve that, Tonegawa’s lab turned to optogenetics, a new technology that allows cells to be selectively turned on or off using light. 

For this pair of studies, the researchers engineered mouse hippocampal cells to express the gene for channelrhodopsin, a protein that activates neurons when stimulated by light. They also modified the gene so that channelrhodopsin would be produced whenever the c-fos gene, necessary for memory formation, was turned on. 

In last year’s study, the researchers conditioned these mice to fear a particular chamber by delivering a mild electric shock. As this memory was formed, the c-fos gene was turned on, along with the engineered channelrhodopsin gene. This way, cells encoding the memory trace were “labeled” with light-sensitive proteins.

The next day, when the mice were put in a different chamber they had never seen before, they behaved normally. However, when the researchers delivered a pulse of light to the hippocampus, stimulating the memory cells labeled with channelrhodopsin, the mice froze in fear as the previous day’s memory was reactivated. 

“Compared to most studies that treat the brain as a black box while trying to access it from the outside in, this is like we are trying to study the brain from the inside out,” Liu says. “The technology we developed for this study allows us to fine-dissect and even potentially tinker with the memory process by directly controlling the brain cells.” 

Incepting false memories

That is exactly what the researchers did in the new study — exploring whether they could use these reactivated engrams to plant false memories in the mice’s brains. 

First, the researchers placed the mice in a novel chamber, A, but did not deliver any shocks. As the mice explored this chamber, their memory cells were labeled with channelrhodopsin. The next day, the mice were placed in a second, very different chamber, B. After a while, the mice were given a mild foot shock. At the same instant, the researchers used light to activate the cells encoding the memory of chamber A. 

On the third day, the mice were placed back into chamber A, where they now froze in fear, even though they had never been shocked there. A false memory had been incepted: The mice feared the memory of chamber A because when the shock was given in chamber B, they were reliving the memory of being in chamber A. 

Moreover, that false memory appeared to compete with a genuine memory of chamber B, the researchers found. These mice also froze when placed in chamber B, but not as much as mice that had received a shock in chamber B without having the chamber A memory activated.

The researchers then showed that immediately after recall of the false memory, levels of neural activity were also elevated in the amygdala, a fear center in the brain that receives memory information from the hippocampus, just as they are when the mice recall a genuine memory. 

These two papers represent a major step forward in memory research, says Howard Eichenbaum, a professor of psychology and director of Boston University’s Center for Memory and Brain.

“They identified a neural network associated with experience in an environment, attached a fear association with it, then reactivated the network to show that it supports memory expression. That, to me, shows for the first time a true functional engram,” says Eichenbaum, who was not part of the research team.

The MIT team is now planning further studies of how memories can be distorted in the brain. 

“Now that we can reactivate and change the contents of memories in the brain, we can begin asking questions that were once the realm of philosophy,” Ramirez says. “Are there multiple conditions that lead to the formation of false memories? Can false memories for both pleasurable and aversive events be artificially created? What about false memories for more than just contexts — false memories for objects, food or other mice? These are the once seemingly sci-fi questions that can now be experimentally tackled in the lab.”

Article Source : Massachusetts Institute of Technology

By Science & Universe

Red bacteria fighting cholesterol for you

What started as a food that astronauts could grow themselves is showing potential for lowering cholesterol levels around the world: space research has found a bacterium that can reduce cholesterol by half.

The origin of this discovery is ESA’s research into self-contained eco systems recycling mission waste into oxygen, food and water. Why take bulky supplies into space when you can engineer your own using the right mix of plants and microorganisms?

The ESA-led Micro-Ecological Life Support System Alternative (MELiSSA) project is tackling this challenge by developing water recycling and looking for ways to cook nutritious meals from less common ingredients.

While they might not sound appetising, bacteria are promising ingredients for space food. They grow exponentially and can provide many nutrients in an astronaut’s diet on a long mission to the Moon or Mars.

As part of its search for the perfect mix of ingredients, the MELiSSA project tested a bacterium, codenamed Red, for safety at the Dutch TNO research institute. 

A bioreactor is basically a vat kept at ideal temperatures and under the right amount of light. By controlling the light, pressure, ingredients and general conditions inside the vat, a bioreactor can ’cook’ many kinds of biomaterials. They can also be used to recycle and treat the waste into edible biomass and for waste water treatment systems, recycling of biological waste and controlled crop growth.

The bacterium was shown to be safe and nutritious but also, remarkably, to cut levels of LDL cholesterol – the ‘bad’ cholesterol.

High levels of cholesterol in the blood increase the risk of heart disease and stroke and 39% of the world’s population have raised levels according to the World Health Organisation. Finding more ways to keep cholesterol in check has obvious benefits.

With ESA’s support, spin-off company EzCOL BV was set up by IPStar BV, MELiSSA’s technology transfer partner, to continue research and market the cholesterol-diminishing bacterium.

Based in the Netherlands, EzCOl has taken over the development under ESA’s Business Incubation Centre in Noordwijk, where they were supported to start their business.

“Our tests demonstrated a reduction in LDL cholesterol levels of up to 50%,” says director Rob Suters of EzCOL.

“We are now scaling up production and doing more tests. All signs show that our product is more effective at lower concentrations than existing cholesterol drugs.” 

The Red bacterium, formally Rhodospirillum rubrum, is a purple Proteobacterium, with a size of 800–1000 nanometres.  It offers several potential uses in biotechnology.

The bacteria are grown in Belgium at MELiSSA’s partner SCK·CEN research centre in vats that need to be kept at ideal temperatures and under the right amount of light.

They could be marketed as a medicine or potentially as a food supplement to existing products.

“Within 18–24 months we will complete our research and be ready to market the technology,” says Rob. “We are already talking to major food producers and pharmaceutical companies.”

Red will not be used by MELiSSA as a cooking ingredient for astronauts because an alga was found to be more suitable for the job. But the nifty bacterium does has another trick up its sleeve: it has proven its worth as a major part of the MELiSSA loop for organic waste and water recycling.

As well as colonising space, Red might soon be conquering supermarkets near you in the fight against cholesterol.

Source : ESA
By Science and universe