On April 26, 1986, history's greatest nuclear accident took place
northwest of the Ukrainian city of Chernobyl. Despite the scale of the
disaster, 25 years later, we still do not know its real effects. An
international team of investigators has shown for the first time that
the colour of birds' plumage may make them more vulnerable to
radioactivity.
Radiation causes oxidative stress, damages biological molecules and
may have "important" negative effects on organisms in relatively high
doses, like those found in certain zones close to Chernobyl.
"In the case of the birds studied, these effects were seen in the
size of their populations," says Ismael Galván, lead author of the study
and researcher in the Laboratory of Ecology, Systematics and Evolution
at the University of Paris-Sur, in France.
According to the study, which has been published in the journal Oecologia,
bird populations fell as the levels of radiation in peripheral zones of
Chernobyl (Ukraine) rose. In total, the researchers analysed the
abundance of 97 bird species exposed to different levels of radiation
during four years.
In the majority of the birds (64 species), the populations diminished
with the level or radioactivity. "Nevertheless, the populations of a
few species (the 33 remaining species) experienced positive effects from
the radiation (though the magnitude of these effects was very low in
some cases), perhaps due to the reduction in competition with other
species," explains Galván.
Colour: a bird's weak or strong point
The scientists concentrated on the colouring generated by melanins --
pigments which protect from ultraviolet radiation and generate
camouflage patterns -- of the nearly one hundred species of bird
studied. The reason: the type of pigmentation may interfere with the
ability to resist radioactivity's negative effects.
"The impact on the populations depends, at least in part, on the
amount of plumage whose colouring is generated by pheomelanin, one of
the two main types of melanins, which produces orangish and brownish
colours," the Spanish expert adds.
The birds of Chernobyl with the most pheomelanism (with the most
plumage coloured by pheomelanin) were judged to be the "most negatively"
affected by the radioactivity. As the pigment consumes glutathione (one
of the antioxidants most susceptible to radiation and whose level tends
to be diminished by its effects), in these birds, the capacity to
combat the oxidative stress generated by radiation "probably"
diminishes.