"Under every stone we turn, we see the dramatic consequences of radiation"
21/04/2016 // Interview // Text: Tobias Moorstedt // All photos courtesy of T. Mousseau

Timothy Mousseau, a renowned biologist from the University of South Carolina, is one of the very few scientists who have visited the disaster sites of Chernobyl and Fukushima. Thirty years after the catastrophic nuclear accident in Ukraine, and five years after a magnitude 9.0 earthquake and a subsequent tsunami severely damaged the Fukushima Daiichi nuclear power plant, no one can evaluate the effects of radioactive contamination on the ecosystem better than Mousseau. 

Professor Mousseau, on April 26, 1986, an explosion in the nuclear power plant in Chernobyl sent a plume of highly radioactive fallout into the air. Would a layperson taking a stroll through the surrounding forest today notice anything unusual?

Timothy Mousseau: Absolutely. An amateur naturalist might observe that there are significantly fewer birds and butterflies flying around in the more radioactive areas in Chernobyl province. Overall, there are far fewer animals of all types in the more radioactive areas. We have also documented a redistribution of species in hot zones on the basis of the species’ relative sensitivity to radioactive contamination.

You have also been to the area around Fukushima. Are there fewer birds and butterflies there as well?

Yes. You have to keep in mind that it is difficult to compare the two sites and incidents, since different amounts of radioactive material and different kinds of isotopes were released. What we are seeing in Fukushima is a rapid decline in the population of radioactivity-sensitive organisms such as birds and butterflies shortly after the incident. Thirty years have passed since the Chernobyl accident, and there seems to be a kind of balance between the effects of radiation and the effects of immigration — an equilibrium between the mortality associated with radioactive contamination and the inflow of new individuals from adjacent areas.

There are reports of abundant wildlife in the restricted zone around Chernobyl — sort of a post-apocalyptic Eden. Is there any truth in that?

It is certainly not some kind of paradise for wildlife! The area was permanently evacuated in 1986. So some mammals such as wild boars and deer that would normally be kept in check by hunting seem to be doing quite well — at least in terms of numbers. Unfortunately, this rebound in population size distracts people from the main question of whether or not radiation effects are influencing the populations. We have published several papers demonstrating that both animals that would normally be hunted and other species show the consequences of radiation in terms of developmental abnormalities, fertility and population size. In Chernobyl the closed-off zone is very large, and there are large areas inside it that are not contaminated very much. In these areas the animals seem to be doing just fine. But in the “hot areas” with high radiation the consequences are dramatic.

Following the evacuation of contaminated areas, many observers registered a rebound of certain animal populations around Chernobyl. Prof. Mousseau's research, however, clearly neglects the idea of a post-apocalyptic refugium.

What prompted your interest in that kind of research?

There were actually two reasons why I was drawn to visit Chernobyl in the late 1990s. First, it was a unique environment that had not been studied very much. Second, the environmental changes were due not to abiotic factors such as rainfall or temperature, but to artificial radiation — which we assumed would lead to mutational genetic effects. I wanted to do studies looking at the evolutionary consequences of elevated mutation rates. Given the importance of mutation rates in evolutionary theory, I thought we might be able to do something fairly new. Also, we were under the impression that many of the organisms in Chernobyl were doing very well, which suggested that there had been an evolutionary response and adaptation to the new stressor. But after a few years we noticed that the plants and organisms were not doing well at all, and we wanted to rigorously document the consequences of radiation.

In a way you were trying to catch evolution in action.

Yes. When we compare the same species in Fukushima and Chernobyl, the animals in Eastern Europe are doing a little bit better, which suggests that there is at least some natural selection going on. That is not a surprise, because whenever the environment changes, plants and animals respond. As long as there is genetic variation in a population and there is some effect of that variation in terms of how well individuals do under the new circumstances, there will be evolution. There are some birds, for example, that have the ability to re-allocate antioxidants, which are helpful for reducing damage to DNA. In normal populations they might be using the antioxidants for other functions, like the coloration of their feathers, but near Chernobyl they are using them as a defense mechanism against radiation — here, it doesn’t pay to be colorful under these circumstances. The main question is if organisms can adapt to the point that they are doing as well or better in the new environment than they would normally do. We have found no evidence of that. Every organism is doing worse. Even bacteria.

How would you describe the genetic fallout of nuclear disasters? How do the elevated mutation rates influence the genotype of certain species in the long run?

These are important questions. Are the mutations exported from the hot areas? Are they building up over time? I would expect that there will be an equilibrium in those populations, reflecting the balance between mutation and selection. As new mutations are added, natural selection will act on the range of genetic variability in a population. Individuals that have a mutation with negative effects will tend to have a shorter life span and fewer offspring. Hence, those genotypes will disappear over evolutionary time.

Prof. Mousseau and his collaborators have registered a broad range of abnormalities among the animal populations around Chernobyl and Fukushima which are believed to be a consequence of exposure to radiation.

Is there a threshold of radiation below which there is no effect?

The impact of radiation on rates of mutation, cancer and mortality varies a good deal by species. But statistically, there is a simple relationship with the dosage: Small dose, small effect — big dose, big effect. In Chernobyl and Fukushima, literally every rock we turn over reveals signs of the mutagenic properties of radiation.

Do you have an example?

There is a study we just published about the cuckoo. Over the years we noticed that cuckoo songs in the hot zones sounded odd. We started to record the songs around Chernobyl and other parts of Europe, and this paper documents higher frequencies of abnormal songs around Chernobyl; often the songs are also shorter. Since we know that the cuckoo’s song is a genetic characteristic, we shouldn’t be surprised that it changes when the level of radiation is high. Another example is the firebug. We noticed that the black pattern on the red back of many bugs, which normally resembles an African face mask, is often disturbed in hot zones. These are visual signs of underlying disturbances in the genetic systems that control the color patterns.

Did you analyze the genetic material of the birds and bugs?

We are actually just starting a project to look at the genetic structure of these mutations. We want to determine if these mutations are somatic or part of the germ line — which would mean that they are transferred from one generation to the next. One of our theories is that because the radiation levels in Fukushima and Chernobyl are relatively low, they don’t usually kill the organisms right away, but make them less fit and shorten their life span. That means that some individuals survive and reproduce — and mutations might accumulate year after year. We are planning large-scale DNA sequencing studies with rodents and also with humans. We want to study the liquidators who helped to clean up after the accidents and the people who grew up around Chernobyl and had children themselves, in order to determine the effects on human DNA.

That is an important question, since the Japanese government is planning to repopulate the area around Fukushima as early as 2017. Has your own attitude toward nuclear energy changed during the period of your work?

On a personal level you come to respect the potential consequences of chronic low-dose exposure to radiation, which are much greater than we originally thought. It doesn’t matter what you feel about nuclear energy per se. We have about 400 reactors in operation around the world and many more under construction. And even if we switched off all the plants at this moment in time, we would have to control the enormous stockpile of spent fuel that can lead to accidents for a very long time. That is why we need to understand the health and environmental consequences of this technology.

Prof. Mousseau and his team are used to work in challenging conditions. QIAGEN's AllProtect, RNAprotect and RNAeasy kits are an indispensable part of his mobile laboratory and help to preserve the precious samples for analysis. 

Will the ecosystems in Fukushima and Chernobyl ever fully recover?

That is hard to say. In the terrestrial ecosystems of Fukushima the consequences will be greatly reduced in the coming decades, because the area with high contamination is relatively small and decreasing every year. The half-life of the dominant contaminant, Cesium 147, is only 30 years. For plants and animals, as the contaminated area gets smaller, immigration from adjacent areas will bring things back to normal. In Chernobyl the situation is more complicated. Because the contaminated land mass is so huge, immigration won’t have such a strong effect. The explosion and the nuclear fire that burned for ten days released a lot of plutonium isotopes and strontium. Some of these isotopes have very long half-lives, measured in thousands of years.

Since you began your studies 17 years ago, technological advances have been immense. How has this influenced your work and your search for insights?

You know, the genetic revolution and advances in molecular biology have really provided us with a large array of new tools that can be used to explore the underlying mechanisms associated with the biological response to radiation and other mutagens. We have been doing our best to employ some of these new methods, which include DNA fingerprinting and, most recently, full genome sequencing.

Are there unanswered questions that you hope to solve with the help of new tools in the future?

Hopefully, the technology will improve and become even more accessible. Scientists like us, who work in the field, are dependent on the research done in the labs of universities and the private sector. One of the big unanswered questions is, Just how much of the genetic damage caused by radiation is repaired before it is transferred to the next generation? What are the mechanisms underlying genetic instability? And are there parts of the genome that are particularly sensitive? If there is one positive aspect of these disasters, it is the fact that they can provide great insights into the mechanisms of evolution itself. 

Timothy Mousseau, 57, received his doctoral degree in 1988 from McGill University, joined the faculty of the University of South Carolina in 1991, and is a professor in the Department of Biological Sciences. He is currently co-editor of the annual review series The Year in Evolutionary Biology and has published over 190 scholarly articles. Mousseau has worked on a variety of organisms ranging from bacteria to beetles to birds. Since 1999 Professor Mousseau has explored the ecological and evolutionary consequences of the radioactive contamination in the regions around Chernobyl and Fukushima. Mousseau’s current research is aimed at understanding the causes of variation among different species in their sensitivity to radionuclide exposure.

To learn more, please visit Prof. Mousseau's website or watch an online lecture on YouTube. If you'd like to learn more about QIAGEN's involvement in Prof. Mousseau's research, please download our background information.

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