At Chernobyl, Birds Adapting to Radiation

abandoned building

The effects of the Chernobyl nuclear accident on the region’s human population is well-documented. But what about the flora and fauna left behind? (Photo credit: Alex Skelly/Flickr/Getty Images)

April 26 marked the 28th anniversary of the Chernobyl nuclear disaster. On this date, a sudden power surge during a reactor systems test at the Chernobyl nuclear power station in Ukraine destroyed Unit 4. The accident and ensuing fire released huge amounts of radiation into the environment.

Twenty-eight workers were killed within the first four months after the accident, and over 100 workers were diagnosed with acute radiation sickness. For the inhabitants of the region, incidences of thyroid cancer skyrocketed, particularly among children and adolescents who drank milk contaminated with radioactive iodine.

A few weeks after the accident, workers constructed a concrete structure (called a sarcophagus) that completely encased the damaged unit. The purpose of the sarcophagus was to limit the further release of radiation into the environment. Officials cut off access to the nuclear power plant, except for a limited number of workers, and set a 30-kilometer (18-mile) exclusion zone around the power plant. Immediately after the accident, 115,000 people were evacuated from the area; within the next few years, an additional 220,000 people were also evacuated from the region and relocated.

Although the impact of the Chernobyl nuclear disaster on the human population has been well-documented, not much is known about the populations of wild plants and animals left behind. A new study published in the journal Functional Ecology describes the impacts of the Chernobyl accident on local bird populations and draws a rather striking conclusion–some birds species have adapted to, and in some cases benefited from, long-term exposure to radiation.

“Previous studies of wildlife at Chernobyl showed that chronic radiation exposure depleted antioxidants and increased oxidative damage,” lead author Dr. Ismael Galvn said in a press release about the research. “We found the opposite that antioxidant levels increased and oxidative stress decreased with increased background radiation.”

Ionizing radiation is made up of particles that are able to free electrons from atoms or molecules and make partially-reduced chemical species called free radicals. The most common of these is reactive oxygen species (ROS). Over time, organisms have evolved a wide-range of antioxidant compounds, which are made in the body by cellular metabolism and can reduce the damaging effects of oxidation.

Most research focused on the biological effects of ionizing radiation has, by necessity, been conducted in the laboratory at the cellular level. Perhaps one silver lining of the Chernobyl accident is that the site is ideal for conducting in situ ecological observations and experiments pertaining to the impacts of radiation on plants and animals.

According to the authors of the journal article: “The high degree of radioactive contamination found in the region of Chernobyl and the relative long time elapsed since the accident make this an excellent scenario for investigating possible mechanisms of adaptation to ionizing radiation in natural populations.”

For their study, the researchers captured birds in mist nets at eight sites within and close to the Chernobyl Exclusion Zone. Captured birds were banded, sexed and aged, and sampled for feathers, blood, sperm, before being released. The researchers caught a total of 152 birds from 16 different species. Background radiation levels were also measured at the exact capture site of each bird.

The scientists measured levels of glutathione (a significant antioxidant, also called GSH), oxidative stress, and DNA damage in the blood samples. They also measured the amount of melanin (a pigment) in the feathers. One type of melanin, called pheomelanin, is a particularly interesting indicator as it depletes antioxidants. As a result, animals that make a large amount of pheomelanin are particularly vulnerable to ionizing radiation.

After analyzing the data, the researchers concluded that glutathione levels and body conditions of the captured birds were not negatively impacted by background radiation. In fact in some cases, glutathione and body condition increased with increased radiation.

Our study provides evidence that birds have physiologically adapted to chronic exposure to radiation at Chernobyl, as radiation levels did not negatively impact their oxidative status, DNA integrity, or physical condition, the scientists reported in the journal article.

The scientists hypothesized that perhaps birds responded to radiation-induced oxidation stress by increasing the amount of antioxidants produced by their bodies. They also found that bird species that exhibited a greater range of feather color (a result of a larger production of pheomelanin) were more negatively impacted by radiation exposure than birds that had less elaborate plumage coloration. In contrast, researchers found that birds that produced another form of melanin, eumelanin, were better protected against oxidative stress and DNA damage.

Birds have the capacity to adapt to chronic exposure to low-dose ionizing radiation, although the capacity varies across species and is particularly reduced in those producing larger amounts of phenomelanin and those that are phylogenetically constrained to mount plastic responses to GSH levels, the study authors concluded. “Our study thus stresses the importance of incorporating a multi-species approach to investigate the biological effects of ionizing radiation as conclusions derived from single-species studies may not represent general trends in taxonomic terms.”

More to Explore

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Chernobyl Accident 1986
Chronic Exposure to Low-dose Radiation at Chernobyl Favors Adaptation to Oxidative Stress in Birds [summary]
At Chernobyl, Hints of Nature’s Adaptation
Some Birds Adapt to Chernobyl’s Radiation

Comments

  1. David Ho says:

    How interesting, I thought that nothing was left alive after Chernobyl.

  2. Andrew Chen says:

    Me too. I thought nothing was left living.

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