NUCLEAR

Analysis is animals birds and insects in the Chernobyl area reported



Chernobyl birds are small brained
By Matt Walker
Editor, Earth News

Marsh warblers are one of the species affected

Birds living around the site of the Chernobyl nuclear accident have 5% smaller brains, an effect directly linked to lingering background radiation.The finding comes from a study of 550 birds belonging to 48 different species living in the region, published in the journal PLoS One. Smaller brain sizes are thought to be linked to reduced cognitive ability.

The discovery was made by a team of researchers from Norway, France and the US led by Professor Timothy Mousseau from the University of South Carolina, US, and Dr Anders Moller from the University of Paris-Sud, France.

Harmful legacy

In April 1986, reactor number four at the Chernobyl Nuclear Power Plant exploded. After the accident, traces of radioactive deposits were found in nearly every country in the northern hemisphere. An exclusion has since been set up around the site of the accident. However, scientists have been allowed inside to gauge the impact the radiation has had on the ecology of the region. Last year Prof Moller and Prof published the results of the largest wildlife census of its kind conducted in Chernobyl - which revealed that mammals are declining in the exclusion zone surrounding the nuclear power plant.The scientists have studied the exclusion zone for more than a decade

Insect diversity has also fallen, and previously, the same researchers found a way to predict which species there are likely to be most severely damaged by radioactive contamination, by evaluating how often they renew parts of their DNA.

In their latest study, the scientists used mist nets to collect birds from eight woodland sites around Chernobyl, which have seen a decline in the numbers of larger animals and small invertebrates living within. After controlling for the differences between species, they found that the birds had brains 5% smaller on average compared to birds not exposed to background radiation. The effect was most pronounced in younger birds, particularly those less than a year old. That suggests that many bird embryos did not survive at all, due the negative effects of their developing brain.

Mechanism unclear

Stressed birds are able to change the size of some of their organs in order to tough out difficult environmental conditions. For example, migrating birds that have travelled long distances often shrink certain organs as they use up energy. But the brain is the last organ to be sacrificed in this way, say the researchers.That suggests the background radiation could be having an even more pronounced effect on other organs within the birds.

It is unclear exactly what mechanism is shrinking the birds' brains. High levels of background radiation cause animals oxidative stress, where they have to use antioxidants in their bodies to fight its ill effects. That leaves animals exposed to radiation severely depleted of antioxidants, and the reduced brain size may be a result of this depletion.

Alternatively, radiation could cause developmental errors in the way the brain grows. However, if that were the case, the scientists say they would expect to see pronounced changes to the size and shape of other parts of the birds' bodies.

Another possibility is that the birds are developing less well as there is less invertebrate prey for them to eat. But the scientists know of no example of the brains of a wild animal shrinking due to a lack of food.

Chernobyl 'not a wildlife haven'
By Mark Kinver
Science and nature reporter, BBC News

The idea that the exclusion zone around the Chernobyl nuclear power plant has created a wildlife haven is not scientifically justified, a study says.

Recent studies said rare species had thrived despite raised radiation levels as a result of no human activity. But scientists who assessed the 1986 disaster's impact on birds said the ecological effects were "considerably greater than previously assumed". The findings appear in the Royal Society's journal, Biology Letters.

The paperand Tim Mousseau 's authors, Anders Moller of University Pierre and Marie Curie, France, from the University of South Carolinaidea that low-level , US, said their research did not support the radiation was not affecting animals. "Recent conclusions from the UN Chernobyl Forum and reports in the popular media concerning the effects of radiation from Chernobyl has left the impression that the exclusion zone is a thriving ecosystem, filled with an increasing number of rare species," they wrote. Instead, they added: "Species richness, abundance and population density of breeding birds decreased with increasing levels of radiation."

The study, which recorded 1,570 birds from 57 species, found that the number of birds in the most contaminated areas declined by 66% compared with sites that had normal background radiation levels. It also reported a decline of more than 50% in the range of species as radiation levels increase.

The findings build on a previous study of barn swallows in the affected area, which showed that the number of the birds declined sharply in contaminated areas. The birds' decline was probably the result of depressed levels of antioxidants after its long migration back to the area, making it more vulnerable to the low-level radiation, the researchers concluded. "It suggests to us that barn swallows are not alone; there are many other species that appear to be affected in a similar way," Professor Mousseau told BBC News.

"This paper also suggests that birds feeding on insects that are living in the upper surface of the soil, where contaminates are highest, seem to be most likely to be missing or depressed." He added that they were currently carrying out research to find out whether the decline was a result of the birds eating contaminated insects, or whether it was a result of fewer insects living in affected areas. "We are also looking for funding to expand the range of ecological studies to include invertebrates, as well as plants and animals."

Radioactive retreat

A recent paper published in the American Scientist magazine suggested that plants and animals were better off in the exclusion zone than specimens outside the 30km radius surrounding the site of the destroyed nuclear reactor. One of the paper's co-authors, Robert Baker from the Texas Tech University, said that the benefits for wildlife from the lack of human activity outweighed the risks of low-level radiation. Writing on his university web page, Professor Baker said: "The elimination of human activities such as farming, ranching, hunting and logging are the greatest benefits. "It can be said that the world's worst nuclear power plant disaster is not as destructive to wildlife populations as are normal human activities."

Professor Mousseau acknowledged Professor Baker's description: "It is true that the Chernobyl region gives the appearance of a thriving ecosystem because of its protection from other human activities. "However, when you do controlled ecological studies, what we see is a very clear signature of negative effects of contamination on diversity and abundance of organisms. We clearly need to be applying scientific method to ecological studies before we can conclude, based on anecdotal observations, that there are no consequences."

20 August 2010

Chernobyl species decline linked to DNA

By Victoria Gill Science reporter, BBC News

Scientists working in Chernobyl have found a way to predict which species there are likely to be most severely damaged by radioactive contamination. The secret to a species' vulnerability, they say, lies in its DNA. This discovery could reveal which species are most likely to decline or even become extinct in response to other types of environmental stress.

The researchers published their findings in the Journal of Evolutionary Biology.

Professor Tim Mousseau from the University of South Carolina, US, and Dr Anders Moller from the National Centre for Scientific Research in Paris, France, led the study. The two scientists have been working in Chernobyl for more than a decade, gathering data about the populations of insects, birds and mammals in "zone of alienation" surrounding the desolate nuclear power station.

One explanation may be that these species have, for whatever reason, less capable DNA repair mechanisms”

For this study, they used existing databases to examine in detail the DNA patterns of each of the species they had studied in Chernobyl.

DNA secret

With every generation of a species' lineage, the pattern of its DNA changes ever so slightly, as a result of the natural balance between mutations and the individual's ability to repair damaged DNA. This is how species evolve. The rate of this change - as each piece of the DNA code is replaced by another - is called the substitution rate. "This information is available in large database," Professor Mousseau explained to BBC News. "So you can get the DNA sequences [of each species] and examine the changes that have occurred among a species over time. What we have discovered is that when we look at the species in Chernobyl, we can predict, based on their substitution rates, which ones are most vulnerable to contaminants."

Migrating birds have been particularly badly affected by the contamination

Professor Mousseau said that the Chernobyl setting offered a "unique opportunity to look at a natural experiment in progress - [to see] what happens to species when they have this kind of environmental perturbation". The results of this study could shed light on which species are most vulnerable to other kinds of environmental contamination. Brightly coloured birds and birds that have a long distance migration were some of the organisms most likely to be affected by contaminants. "One explanation may be that these species have, for whatever reason, less capable DNA repair mechanisms," said Professor Mousseau.

Dr Louise Johnson, an evolutionary biologist from the University of Reading, said the findings were "fascinating". "Extreme events like Chernobyl provide opportunities to test predictions about evolution," she told BBC News. "One of the difficulties of such research is that it isn't really an experiment- it is impossible to control for all of the confounding variables. "But [the scientists] have been very careful to test all of the other factors that could be important - antioxidants, population size, body size, etc. of bird species and it appears... that there is a shared causal relationship between accumulating mutations over time and the ability to withstand radiation."

Chernobyl zone shows decline in biodiversity

By Victoria Gill Science reporter, BBC News

 

The largest wildlife census of its kind conducted in Chernobyl has revealed that mammals are declining in the exclusion zone surrounding the nuclear power plant. The study aimed to establish the most reliable way to measure the impact on wildlife of contamination in the zone. It was based on almost four years of counting and studying animals there.

The scientists say that birds provide the best "quantitative measure" of these impacts.They report their findings in the journal Ecological Indicators. The research team say that their census of species in the zone - which was carried out for more than three years - provides more evidence that contamination has a "significant impact" on biodiversity.

Professor Timothy Mousseau from the University of South Carolina, US, and Dr Anders Moller from the University of Paris-Sud, France, worked together on the project. From 2006-09, they counted and examined wildlife including insects, amphibians, reptiles, birds and mammals. Their previously published work revealed some of the negative impacts on birds and on insects of the low-level radiation that still contaminated the exclusion zone surrounding the power plant. The new data on mammals and reptiles shows what Professor Moussaeu described as a "strong signal" of reduced biodiversity in these groups too.

The research team compared the abundance of species in the exclusion zone with similar types of habitats in the area, which were not contaminated. "The truth is that these radiation contamination effects were so large as to be overwhelming," Professor Mousseau told BBC News.

During their census work, he and Dr Moller have also examined the effects of radiation contamination on the animals. They say that these impacts are particularly obvious in birds. In their studies on barn swallows, the team observed birds with tumours on their feet, necks and around their eyes. "We think they may be more susceptible, after their long migrations, to additional environmental stress," explained Professor Mousseau.

Scientists in Ukraine criticised the conclusions. Dr Sergii Gashchak, a researcher at the Chornobyl Center in Ukraine was not available for comment on this latest paper. But he spoke to BBC News last year and dismissed the team's previous findings on insects and birds. He said that he drew "opposite conclusions"."Wildlife really thrives in Chernobyl area - due to the low level of [human] influence," Dr Gashchak told BBC News."All life appeared and developed under the influence of radiation, so mechanisms of resistance and recovery evolved to survive in those conditions," he continued.

But Professor Mousseau said the evidence of an increase in biodiversity in the region is "purely anecdotal". "This is the first paper that provides quantitative, rigorous data that the mammals really are significantly affected by contamination," he told BBC News. "That said - it's not a bad idea to set this place up as a wildlife haven - it's a natural laboratory where we can study the long-term consequences of this kind of an accident." Dr Mousseau also criticised a recently made documentary film called Chernobyl, A Natural History, which has been promoted by a French production company as showing how nature has "recolonised" the exclusion zone in the absence of man. Professor Mousseau said: "If society is ever to learn more about the long term environmental consequences of large scale accidents - and Chernobyl is just one of several - it is important that we all take our responsibilities seriously."


Chernobyl 'shows insect decline'
By Victoria Gill
Science reporter, BBC News

Two decades after the explosion at the Chernobyl nuclear power plant, radiation is still causing a reduction in the numbers of insects and spiders.

According to researchers working in the exclusion zone surrounding Chernobyl, there is a "strong signal of decline associated with the contamination". The team found that bumblebees, butterflies, grasshoppers, dragonflies and spiders were affected. They report their findings in the journal Biology Letters.

Professor Timothy Mousseau from the University of South Carolina, US, and Dr Anders Moller from the University of Paris-Sud worked together on the project. The two researchers previously published findings that low-level radiation in the area has a negative impact on bird populations.

"We wanted to expand the range of our coverage to include insects, mammals and plants," said Professor Mousseau. "This study is the next in the series."

Ghost zone

Professor Mousseau has been working for almost a decade in the exclusion zone. This is the contaminated area surrounding the plant that was evacuated after the explosion, that remains effectively free of modern human habitation.

For this study they used what Mousseau described as "standard ecological techniques" - plotting "line transects" through selected areas, and counting the numbers of insects and spiders webs they found along that line. At the same time, the researchers carried hand-held GPS units and dosimeters to monitor radiation levels. "We took transects through contaminated areas in Chernobyl, contaminated land in Belarus, and in areas free of contamination. What we found was the same basic pattern throughout these areas - the numbers of organisms declined with increasing contamination."

According to Professor Mousseau, this technique of counting organisms is "particularly sensitive" because it can account for the changing pattern of contamination across the zone. "We can compare relatively clean areas to the more contaminated ones," he explained.

Professor Mousseau said that his aim is to use the site to discover the true ecological effects of radiation contamination. "The verdict is still out concerning the long-term consequences of mutagenic contaminants in the environment," he said. "Long-term studies of the Chernobyl ecosystem offer a unique opportunity to explore these potential risks that should not be missed."

Chernobyl Radiation Patterns

The spread of radioactive contaminates into the atmosphere from the Chernobyl accident was eventually detected all over the world. Events, such as volcano eruptions and nuclear bomb testings, result in major effluent emission that also can be detected with very sensitive equipment.

The risk to the public health of the people in neighboring countries from the nuclear accident at Chernobyl, USSR, has been a primary element in evaluating the magnitude this accident has had on the world. The citizens of eastern Europe and Scandinavia are the most concerned, because their countries received the majority of the exposure in the first week of the accident and thus, their health is at the highest risk.

On Friday, April 25, 1986, as a result of human error during experiments being performed by the staff at Chernobyl, the cooling system failed resulting in the melting of fuel and, of greater importance to the public, the graphite moderator ignited and began the release of what has been approximated as 1900 PBq [1] of activity to the environment (it has been commented that had there been a containment building similar to the ones used in U.S. reactors, this value might have been greatly reduced). The most hazardous isotopes released in this accident are known to Cs-137, I-131, and Sr-90. These isotopes have half-lives sufficiently long to allow them to migrate into the body or, in the case of Iodine, have the tendency to accumulate in the thyroid gland.

The plume from the burning graphite initially traveled in a northwest direction toward Sweden, Finland and eastern Europe, exposing the public to levels up to 100 times the normal background radiation. A very serious concern involves the contamination of grain and dairy products from fallout. This contamination presents the chance for permanent internal contamination. Both Sr-90 and I-131 migrate to vital organs in the body where they are impossible to remove, serving as a constant source of unnecessary radiation and as a cause of cancer or other diseases.

Regions of heaviest fallout from the effluents from the fire at Chernobyl are shown in the figure below (Map shows borders in 1986). In these regions radiation exposure exceeded 100 mrads/h (0.1mrem/hr or 0.001mSv/hr) [4].