Wildlife Of Chernobyl

Introduction of the accident and further research

The reactor in Chernobyl Nuclear power Plant exploded during a technical test on April 26, 1986. Due to this, people were permanently evacuated from the area of the disaster. The accident had a severe impact on the environment, human population and biodiversity. Today, this forbidden area of high radioactivity is called the Exclusion Zone, that covers approximately 2,600 km2 in Ukraine and Belarus (Deryabina et al. , 2015; Beresford et al. , 2016).

The Chernobyl disaster has led to extensive radioecological studies on long-term radiation exposure and further effects on plants and animals. There are large numbers of various species exposed to different doses of radiation that lead to studies ranging from DNA damage to animal populations. Today, despite the negative impacts of radioactivity, the restricted zone provides an abundance refuge for many endangered animal species (bison, wolves, wild horses) (Beresford et al. , 2016; Helmenstine, 2019).

Radioactivity

The main types of radioisotopes around Chernobyl are Strontium-90, Cesium-137 and Iodine-131. These radioisotopes causing irradiation, affect people, animals and are also accumulated in the food chains (Beresford et al. , 2016).

The energy from radiation can damage or break DNA molecules. If the damage is severe, cells cannot be replicated, and the organism dies. Or can cause a mutation, mutated DNA may lead to cancer and affect an ability to reproduce. If a mutation occurs in gametes, it can result in embryo damage or birth defects (Helmenstine, 2019). In fact, radiation poisoning can cause over the next generations a reduction in the size of organisms. This is because growth and development require energy, and an organism must expend the energy on fighting with radiation damages. (Helmenstine, 2019). Therefore, one of the radiation effects is a shorter lifespan of most animals (BBC Future, 2019).

Population and Biodiversity

Radiation has serious effects on soil-dwelling invertebrate populations in the most contaminated areas. There is a high mortality of eggs and early life stages of invertebrates (bees, butterflies, spiders, and dragonflies) (Møller and Mousseau, 2009; Beresford et al. , 2016). A study of vertebrates has shown no decline in abundance or diversity, even in communities of contaminated lakes at dose-rates about 30Gy. The long-term effects of radiation on animals with long lifespan are unclear (Beresford et al. , 2016).

The population of European bison (Bison bonasus) in Chernobyl is increasing (National geographic, 2015). The lack of hunting in the zone and thriving wildlife provides pray for bears and other predators. Therefore, lynxes and foxes are common animals in the exclusive zone. There is also a large population of wild dogs, descends of dogs left behind by people that were forced to evacuate the area (Helmenstine 2019; Deryabina et al. , 2015). Brown bears (Ursus arctos) had not been observed in the area for a century. In 2014 photographic evidence of their return was provided (BBC, 2014). The wolf (Canis lupus) population in the exclusion zone is more than seven times bigger than outside of the area. (Deryabina et al. , 2015). The wolves from Chernobyl have been so successful, that there are concerns about spreading genetic mutations by breeding with wolves outside the zone. Therefore, those wolves and their travels are monitoring by tracking collars (National geographic, 2018).

However, birds in the Chernobyl zone are an example of animals that face problems from radiation exposure. A study of barn swallows (Hirundo rustica) from 1991 to 2006 found out that birds in the radioactive zone displayed more abnormalities, including deformed beaks, albinism, brain damage, bent tail feathers, and deformed air sacs. Observed birds in the exclusion zone had less reproductive success (Møller et al. , 2011; Beresford et al. , 2016; Helmenstine 2019).

BBC (2019) “Chernobyl: The end of a three-decade experiment”, available at: https://www. bbc. co. uk/news/science-environment-47227767

The Przewalski’s horse (Equus ferus przewalskii) is the last remaining species of the wild horse in the world. The horse became 'extinct in the wild', and the population dropped to 13 breeding horses, in München and Prague zoos. Breeding programs were successful, and horses were reintroduced to Chernobyl and Mongolia (Kardová L. , 2012). The wild horses were imported to Chernobyl in 1998 as part of a conservation experiment to reduce the risk of wildfires (Kardová L. , 2012; BBC, 2019). These endangered horses are doing well due to the lack of human activity.

After the accident, trees were killed in an area covering 5km2. The zone of the dead forest was named the “Red Forest” as the first sign of radiation damage was leaves turning red and brown as they died. Less severe damage was seen over a wider area up to 120 km2, affected by doses of 5Gy. In deciduous trees, the premature loss of leaves was observed, as a response to radiation. Studies of pine trees (Pinus sylvestris) have reported that mutations are decreasing. However, evidence of cytogenetic damage in seedlings of trees in Chernobyl is still present (Beresford et al. , 2016).

Result of scavenger test

Recent studies (Schlichting et al. , 2019) using camera traps have discovered that semiaquatic animals and other scavengers, like minks and otters, are doing significantly well in the exclusion zone. Fish carcasses were placed near the riverbanks to find out what species would appear to feast on them.

98% of all fish were consumed by wild animals within one week. Scientists were able to record animals from the family of Mustelidae, Muridae, Canidae to Corvidae, and even raptors from family Accipitridae. The fact that the fish were eaten so quickly indicates that there is a high rate of scavenging occurring in the area.

There were documented 15 different vertebrate species composed of 10 mammalian and 5 avian species. Among the most common small scavengers were three mice species (Apodemus agrarius, flavicollis and Micromys minutus), Eurasian jays (Garrulus glandarius), and Common magpies (Pica pica). The average biomass consumed by mice and corvids was 8%. Larger scavengers that completely consumed carcasses, when they found it, includes Raccoon dogs (Nyctereutes procyonoides), American mink (Neovison vison), Eurasian otter (Lutra lutra), wolves (Canis lupus), ravens (Corvus corax), and White-tailed eagle (Haliaeetus albicilla). Raccoon dogs and American minks were the predominant scavengers and consumed 48. 73% of biomass.

Cooling Pond radiation measurements and impact

Different kinds of fish from a cooling pond, water reservoirs and lakes polluted by radionuclides, have been studied after the Chernobyl accident. The highest concentration of 137Cs was registered in fish inhabiting the cooling pond (Imanaka, T. , 2002; Ryabov, I. N. , 2014). Furthermore, an increased rate of DNA damage was observed in fish from the cooling pond compared to other water reservoirs. Biological consequences were found in all examined fish, particularly in the reproductive system and morphology of fish. Less often anomalies were spotted in body proportion, combined with damages of scales and fins. The largest quantity of abnormalities in the reproductive system has been registered in predatory fish (Ryabov, I. N. , 2014; Sugg et al. , 1996; Lerebours et al. , 2018).

Increased sterility and gonad abnormalities were shown in silver carp (Hypophthalmichthys molitrix) in the Chernobyl cooling reservoir at dose rates of 10Gy (Beresford et al. , 2016).

The study also examined the amount of contamination and genetic damage associated with 137Cs in catfish (Silurus glanis) from the cooling pond. In general, catfish from the cooling pond exhibited genetic damage, and the amount of damage was related to the concentration of 137Cs in individual fish (Sugg et al. , 1996). Chernobyl's cooling pond offers to the catfish populations an isolated habitat, that is free from predators and full of prey and allow them to grow consistently into an enormous size. Catfish are active predators and scavengers, known to feed on fish, amphibians, worms, birds and even small mammals (Imanaka, T. , 2002).

Conclusion and signs of adaptation

Wildlife is doing much better than scientist has predicted. It has been 33 years, and organisms are already showing signs of adaptation. Some animals as frogs, bank voles and birds inside the zone have shown a change in their colouration and other small chemical changes (Boratyński et al. , 2014). It seems (BBC Future, 2019) that plants in Chernobyl are using a mechanism to protect their DNA, altering their metabolism to be more resistant, and turning on the repair systems, to replace cells that are damaged more quickly. Plants also have shown a change of colour and deeper root systems. For better understanding, further research is needed in every branch.

References:

1. BBC (2014) “Brown bears return to Chernobyl after a century away”. Available at: https://www. bbc. co. uk/news/science-environment-30197341 [Accessed 28 Nov. 2019].
2. BBC (2019) “Chernobyl: The end of a three-decade experiment”. Available at: https://www. bbc. co. uk/news/science-environment-47227767 [Accessed 29 Nov. 2019].
3. BBC Future (2019) “How plants reclaimed Chernobyl's poisoned land”. Available at: https://www. bbc. com/future/article/20190701-why-plants-survived-chernobyls-deadly-radiation [Accessed 29 Nov. 2019].
4. Beresford, N. A. , Fesenko, S. , Konoplev, A. , Skuterud, L. , Smith, J. T. and Voigt G. (2016) “Thirty years after the Chernobyl accident: What lessons have we learnt?”, Journal of Environmental Radioactivity, 157, pp. 77-89.
5. Boratyński, Z. , Lehmann, P. , Mappes, T. , Mousseau T. A. and Møller, A. P. (2014) “Increased radiation from Chernobyl decreases the expression of red colouration in natural populations of bank voles (Myodes glareolus)”, Scientific reports, 4(1).
6. Deryabina, T. G. , Kuchmel, S. V. , Nagorskaya, L. L. , Hinton, T. G. , Beasley, J. C. , Lerebours, A. and Smith J. T. (2015) “Long-term census data reveal abundant wildlife populations at Chernobyl”, Current Biology, 25(19), pp. R824-R826.
7. Helmenstine M. A. (2019) “What we know about the Chernobyl animal mutation”, ThoughtCo Animals and Nature available at: https://www. thoughtco. com/chernobyl-animal-mutations-4155348 [Accessed 30 Dec. 2019].
8. Imanaka, T. (2002) “Recent research activities about the Chernobyl NNP accident in Belarus, Ukraine and Russia”, Research reactor institute, Kyoto University, pp 3-131.
9. Kardová, L. (2012) “Extension of Przewalski horses in the Czech Republic”, University of South Bohemia in České Budějovice, Faculty of Agriculture, pp10-45. Thesis in Czech language available at: https://theses. cz/id/3mgpu3/Historie_kon_Pevalskho_v_esk_republice. pdf?lang=en [Accessed 30 Dec. 2019].
10. Lerebours, A. , Gudkov, D. , Nagorskaya, L. , Kaglyan, A. , Rizewski, V. , Leshchenko, A. , Bailey, E. H. , Adil Bakir Ovsyanikova, S. , Laptev, G. and Smith, J. T. (2018) „Impact of Environmental Radiation on the Health and Reproductive Status of Fish from Chernobyl”, Environmental Science & Technology, 52(16), pp. 9442-9450. Møller, A. P. , Bonisoli-Alquati, A. , Rudolfsen, G. and Mousseau, T. A. (2011) “Chernobyl Birds Have Smaller Brains”, PLoS ONE, 6(2), p. e16862.
11. Møller, A. P. and Mousseau, T. A. (2009) “Reduced abundance of insects and spiders linked to radiation at Chernobyl 20 years after the accident”, Biology Letters, 5(3), pp. 356-359.
12. National geographic (2015) “Chernobyl and other places where animals thrive without people”. Available at: https://www. nationalgeographic. com/news/2015/10/151008-chernobyl-animals-thrive-without-people-science/ [Accessed 27 Nov. 2019].
13. National geographic (2018) “Could Chernobyl wolves be spreading mutation”. Available at: https://www. nationalgeographic. com/animals/2018/07/chernobyl-wolves-radiation-mutation-animals/ [Accessed 29 Nov. 2019].
14. Ryabov, I. N. (2014) “Long-Term Observation of Radioactivity Contamination in Fish around Chernobyl”, Leninski pr. 33, Moscow, 117071, Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences pp. 112-122.
15. Schlichting, P. E. , Love, C. N. , Webster, S. C. , Beasley J. C. (2019) “Efficiency and composition of vertebrate scavengers at the land-water interface in the Chernobyl Exclusion Zone”, Food Webs, 18, p. e00107.
16. Sugg, D. W. , Brooks, J. A. , Jagoe, C. H. , Smith, M. H, Chesser, R. K. , Bickham, J. W. , Lomakin, M. D. , Dallas, C. E. and Baker, R. J. (1996) “DNA damage and radiocesium in channel catfish from chernobyl”, Environmental toxicology and chemistry, 15(7), pp. 1057-1063.