Birds in the exclusion zone around Chernobyl are adapting to – and may even be benefiting from – long-term exposure to radiation, ecologists have found. The study, published in the British Ecological Society's journal Functional Ecology, is the first evidence that wild animals adapt to ionising radiation, and the first to show that birds which produce most pheomelanin, a pigment in feathers, have greatest problems coping with radiation exposure.
According to lead author Dr Ismael Galván of the Spanish National Research Council (CSIC): "Previous studies of wildlife at Chernobyl showed that chronic radiation exposure depleted antioxidants and increased oxidative damage. We found the opposite – that antioxidant levels increased and oxidative stress decreased with increasing background radiation."
The Chernobyl disaster, which occurred on April 26 1986, had catastrophic environmental consequences. However, because it remains heavily contaminated by radiation, the region represents an accidental ecological experiment to study the effects of ionising radiation on wild animals.
Laboratory experiments have shown that humans and other animals can adapt to radiation, and that prolonged exposure to low doses of radiation increases organisms' resistance to larger, subsequent doses. This adaptation, however, has never been seen outside the laboratory in wild populations.
Previous studies of the level of antioxidants and oxidative damage at Chernobyl are limited to humans, two bird species and one species of fish. Because different species vary widely in their susceptibility to radiation, this limited data has made it difficult to study how wild animals adapt to radiation exposure.
The researchers, including ecologists who have worked around Chernobyl since the 1990s, used mist nets to capture 152 birds from 16 different species at eight sites inside and close to the Chernobyl Exclusion Zone. They measured background radiation levels at each site, and took feather and blood samples before releasing the birds.
They then measured levels of glutathione (a key antioxidant), oxidative stress and DNA damage in the blood samples, and levels of melanin pigments in the feathers. Melanins are the most common animal pigments but because the production of pheomelanin (one type of melanin, the other type being eumelanin) uses up antioxidants, animals that produce the most pheomelanins are more susceptible to the effects of ionising radiation.
As well as taking samples from 16 different bird species, the team used a novel approach to analyse their results. The method takes better account of how closely related different species are. This is important because some species are more susceptible to radiation than others. The method focuses the analysis on individual birds instead of species averages, making it a much more sensitive way to analyse biochemical responses to radiation.
The results revealed that with increasing background radiation, the birds' body condition and glutathione levels increased and oxidative stress and DNA damage decreased. They also showed that birds which produce larger amounts of pheomelanin and lower amounts of eumelanin pay a cost in terms of poorer body condition, decreased glutathione and increased oxidative stress and DNA damage.
Levels of radiation in the study area ranged from 0.02 to 92.90 micro Sieverts per hour. The 16 bird species surveyed were: red-backed shrike; great tit; barn swallow; wood warbler; blackcap; whitethroat; barred warbler; tree pipit; chaffinch; hawfinch; mistle thrush; song thrush; blackbird; black redstart; robin and thrush nightingale.
Ionising radiation damages cells by producing very reactive compounds known as free radicals. The body protects itself against free radicals using antioxidants, but if the level of antioxidants is too low, radiation produces oxidative stress and genetic damage, which leads to ageing and death.
Explore further:
Chernobyl's radioactivity reduced the populations of birds of orange plumage
More information:
"Chronic exposure to low-dose radiation at Chernobyl favors adaptation to oxidative stress in birds." Ismael Galván, et al. Functional Ecology, Friday 25 April 2014.. DOI: 10.1111/1365-2435.12283
Egleton
philw1776
BobSage
Modernmystic
Huh? That doesn't sound correct. The average world background radiation is 0.87 mSv/a (milli sieverts/hour). Now a MICRO Sievert is 1/1000th of a milli Sievert. So the radiation they're being exposed to is far below average background as I read it.
Background radiation;
http://en.wikiped...adiation
I'm thinking they meant to say milli instead of micro?
antialias_physorg
mSv/a means milliSievert per year ("a" stands for "annum")
Modernmystic
Modernmystic
http://en.wikiped...adiation
So my guess is that it's a misprint under the first picture caption and it should read 0.87 μSv/h?
It can't be both...
TheGhostofOtto1923
-And you can too boys and girls! Radiation is our friend.
Although it might take a number of gens.
kpwalkin
katesisco
Let's suppose it happened to us 5 my ago, and we ate chunks of cooked meat which allowed our bodies to make more protein which protected us from local low level radiation. And after millenea, the radiation levels fell off and guess where that extra protein went? Into brain size.
katesisco
According to lead author Dr Ismael Galván of the Spanish National Research Council (CSIC): "Previous studies of wildlife at Chernobyl showed that chronic radiation exposure depleted antioxidants and increased oxidative damage. We found the opposite – that antioxidant levels increased and oxidative stress decreased with increasing background radiation."
Obviously the protein that went into a luxurious display of feathers was nixed in favor of life extension. Radiation is not good for you.
Jimee
Jimee
ryggesogn2
Captain Stumpy
@Modernmystic
does this link help?
http://wpedia.goo...isievert
Modernmystic
Extremely helpful Capn' thanks!
There seems to be some disagreement amongst various sites on wheter or not microsieverts are larger than millisieverts on conversion tables. However it's my understanding that micro is a millionth and milli is a thousanth. That being the case the radiation they're talking about 0.02 to 92.90 micro Sieverts is actually lower than the Earth's average background radiation.
92*24*365=805,920 microsieverts/year. That's less than 1 sievert per year. The world average is 3.01 sieverts/ year...so something still doesn't sound right.
Modernmystic
This map shows daily readings of radiation levels in Japan including around Fukushima
http://jciv.iidj.net/map/
The units are in nanosieverts (billionths of a sievert) per hour.
If you zoom right in on Fukushima Dai-ichi you get a reading of about 120,000 nanosieverts, which sounds like a lot. However after the following math:
120,000*24*365=1,051,200,000 nanosieverts/year...which of course is only 1.05 sieverts....
That's less than the world's background right on top of that reactor.