Behaviour of birds and worms at Chernobyl

Date:18/10/2007 URL: http://www.thehindu.com/thehindu/seta/2007/10/18/stories/
2007101850081500.htm
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Sci Tech



Behaviour of birds and worms at Chernobyl
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Lot of variation among species and within species
Strong correlation between internal dose, radiation level
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Recent studies of birds at Chernobyl revealed some strange behaviour of certain species. Anders Moller at Pierre and Marie University in Paris and Tim Mousseau at the University of South Carolina found that the bird species, pied flycatcher and the great tit (Parus major), generally avoided nesting boxes kept at high levels of background radiation. Pied flycatcher exhibited stronger effect. Radiation levels at some nest sites were as much as 2,000 times the natural levels elsewhere in the world (New Scientist, March, 28, 2007).
Nest site choice
“Inter specific differences in effects of radiation on nest-site choice suggest that species respond in a species-specific manner to radiation,” they claimed (Proc. Roy.Soc. Biology, March 27, 2007).
Their claim may not be valid as they did not consider internal doses which were substantial. “We cannot agree more that internal dose is most important. We have…measured dose rate of over 300 birds around Chernobyl. There is a very strong correlation between internal dose and radiation level at the site of capture,” the authors responded. Ukrainian scientists coordinated the study of internal body burden estimates.
“… the preliminary results suggest considerable variation among species and individuals within species, even those living in the same general area. We hope to fully explore these data once our colleagues have finished with the primary publication,” Dr Mousseau clarified.
Once Time magazine noted that yellow legged mud-dauber wasps at the Oak Ridge National Laboratory use mud containing radioactivity to build their nests whereas pipe-organ mud-daubers use only non-radioactive mud, though the same source of nest materials was available to both ( http://www.time.com/time/printout/0,8816,897250,00.html).
Dr Mousseu had seen mud-dauber tubes at the Savannah River site. “I will investigate the possibility of measuring activity in the mud,” he promised in an e-mail message. He noted that barn swallows, the bird species studied extensively at Chernobyl also build their nest in the area!
Three species studied
Certain species of worms in the lakes in Chernobyl behaved strangely! Scientists studied three species contaminated by radioactivity from the Chernobyl accident; greater proportions of two species of worms started seeking partners for sex, switching from asexual to sexual reproduction. Ukrainian scientists believe that they did it to increase their chance of survival (EurekAlert, April 9, 2003).
The third species showed double the rate for asexual reproduction in the polluted lake (Journal of Env. Radioactivity, 2003).
Background radiation in certain areas of Kerala and Tamil Nadu is above normal (far too less than that in Chernobyl).
I asked Dr Mousseau whether the study of insects and other invertebrates in such high background radiation areas (HBRA) is of any interest.
“It would seem to me that this region would likely reveal some very interesting adaptations to radiation that might not have had time to evolve in other regions”, he conceded. “…it would be important to focus on a few key species that occur in this area and examine survival and reproduction with control sites.
Similarly, it would be valuable to examine the community of organisms, especially insects, to determine if species composition changes in a predictable way.
Either way, I suspect that this region would be an excellent target for further investigation and my suspicion is that one would be very likely to generate many exciting discoveries of organismal responses to this environmental effect”, he asserted.
No scientific basis
Learned national academies and international agencies should support a dedicated research project to study the flora and fauna in the HBRA.
Radiation biologists, geneticists, biotechnologists and radiation physicists must carry it out.
The International Commission on Radiological Protection has realised that its old concept that if man is protected, other organisms will be protected has no scientific basis.
K. S. PARTHASARATHY
FORMER SECRETARY, AERB
( ksparth@yahoo.co.uk)
© Copyright 2000 - 2007 The Hindu

Prettiest birds the hardest hit in Chernobyl

Date:04/10/2007 URL: http://www.thehindu.com/thehindu/seta/

2007/10/04/stories/2007100450091500.htm
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Sci Tech



Prettiest birds the hardest hit at Chernobyl
Birds with bright, colourful plumage registered the strongest decline
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Radiation produces free radicals which damage DNA and other molecules permanently
Four groups of birds which suffered most had high expenditure of antioxidants
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At 01:23 hrs on 26 April 1986, the severest nuclear accident occurred at the Chernobyl Nuclear Power Station in Ukraine. Radioactive materials from the stricken reactor got released over the next ten days. Large areas got heavily contaminated. Initially, vast tracts of pine forests close to the site perished. Over the next few years, the lands recovered their green cover.
Recent reports claimed that animals like wild boar, wolves and moose had flourished in the 40 mile diameter exclusion zone (The New York Times, August 28, 2007).
‘Defying predictions’
“Contrary to the myths and imagery, Chernobyl’s land had become a unique, new ecosystem. Defying the gloomiest predictions, it had come back to life as Europe’s largest nature sanctuary, teeming with wildlife”. Mary Mycio who visited Chernobyl in 1996 described “the lands extraordinary resurrection” in ‘Wormwood Forest, A Natural History of Chernobyl.’
However, Dr. A.P. Moller and Dr T.A. Mousseau who carried out scientific studies of birds noted that population of the prettiest birds with bright, colourful plumage registered the strongest decline with radiation (Journal of Applied Eco logy, July 11, 2007). Population density of species of birds with long distance migration and dispersal and large eggs also declined with radiation level.
“Species richness, abundance and population density of breeding birds decreased with increasing levels of radiation even after controlling statistically for the effects of potentially confounding factors such as soil type, habitat, and height of vegetation” the researchers observed (Biology letters, August 14, 2007).
The researchers used point count census of 57 species of birds at 254 locations in the forests around Chernobyl to establish the relationship between abundance of birds and radiation levels.
Scavengers
Radiation produces free radicals which damage DNA and other molecules in living cells permanently. Antioxidants are free radical scavengers. They protect tissues against radiation damage.
Moller and Mousseau suggested that if antioxidants are a limited resource in the body, individuals with a high expenditure of antioxidants may suffer most from radiation. Pretty birds spent large amounts of carotenoids (these are antioxidants) in their colourful plumes, losing them irrecoverably.
Physical activity
Birds that migrate over large distances spent large amounts of antioxidants during their extreme physical activity. Birds which lay large eggs have lower levels of antioxidants as they deposit most of it in their eggs.
The researchers argued that the four groups of birds which suffered most had high expenditure of antioxidants (Journal of applied Ecology, 2007).
Important implications
“While the present study has implications for the study of animals living in radioactively contaminated areas such as Chernobyl… it may also have important implications for animals elsewhere. There is large variation in natural levels of radioactivity as a result of variation in abundance of radioactive isotopes…There are no studies of the biological consequences of such variations in natural levels of radioactivity, but we suggest that some of the consequences can be predicted from the present study”, the authors claimed.
The researchers expected that individuals of bird species with carotenoid-based plumage to have paler plumage colour in Chernobyl than individuals from control sites.
Similarly, we may expect that ladybird which has the highest number of carotenoids among insects may have paler hues in the high natural background radiation areas (HBRA) of Kerala. The radiation levels in HBRA are relatively low compared to those in Chernobyl.
Lesser range
But ladybirds in HBRA may get exposed to significant radiation doses as they have less range and may be considered to be relatively immobile compared to birds!
Any insect lover can test the hypothesis by carrying out a survey in HBRA for a few days!
Ladybirds may be radiation resistant. Scientists sent C.elgans, a type of round worm, which has been genetically mapped, in the stricken shuttle Columbia to study space radiation effects.
They survived the disaster. Cousins of these survivors may be present in HBRA!
K.S. PARTHASARATHY
Former Secretary, AERB ( ksparth@yahoo.co.uk)
© Copyright 2000 - 2007 The Hindu