Variation in chronic radiation exposure does not drive life history divergence among Daphnia populations across the Chernobyl Exclusion Zone

Abstract

Ionizing radiation is a mutagen with known negative impacts on individual fitness. However, much less is known about how these individual fitness effects translate into population‐level variation in natural environments that have experienced varying levels of radiation exposure. In this study, we sampled genotypes of the freshwater crustacean, Daphnia pulex , from the eight inhabited lakes across the Chernobyl Exclusion Zone (CEZ). Each lake has experienced very different levels of chronic radiation exposure since a nuclear power reactor exploded there over thirty years ago. The sampled Daphnia genotypes represent genetic snapshots of current populations and allowed us to examine fitness‐related traits under controlled laboratory conditions at UK background dose rates. We found that whilst there was variation in survival and schedules of reproduction among populations, there was no compelling evidence that this was driven by variation in exposure to radiation. Previous studies have shown that controlled exposure to radiation at dose rates included in the range measured in the current study reduce survival, or fecundity, or both. One limitation of this study is the lack of available sites at high dose rates, and future work could test life history variation in various organisms at other high radiation areas. Our results are nevertheless consistent with the idea that other ecological factors, for example competition, predation or parasitism, are likely to play a much bigger role in driving variation among populations than exposure to the high radiation dose rates found in the CEZ. These findings clearly demonstrate that it is important to examine the potential negative effects of radiation across wild populations that are subject to many and varied selection pressures as a result of complex ecological interactions.

Towards solving a scientific controversy – The effects of ionising radiation on the environment

“…As an example, several reproductive parameters were measured in a range of freshwater organisms from the CEZ. No significant alterations to reproductive fitness were detected in the crustaceans Asellus aquaticus (Fuller et al, 2018) and Daphnia pulex (Goodman et al, 2019). Whilst fish species (Rutilus rutilus and Perca fluviatilis) were found to in generally good reproductive health, a delay in the maturation of the gonads was evident for P. fluviatilis in the most contaminated lakes (this was not observed for R. rutilus) (Lerebours et al, 2018).…”

“…The mechanisms involved in organism responses to chronic radiation exposure, both within and between generations, are the subject of an active debate in the scientific literature (e.g. Boubriak et al, 2016;Carroll et al, 2007;Goodman et al, 2019;Horemans et al, 2019). Whilst adaptation of organisms to radiation within the CEZ has been suggested (Møller and Mousseau, 2016;Boubriak et al, 2008), it has not yet been the focus of any comprehensive research programme.…”

From tangled banks to toxic bunnies; a reflection on the issues involved in developing an ecosystem approach for environmental radiation protection

“…Other papers have reported little or no effect (e.g. Deryabina et al 2015;Bonzom et al 2016;Lerebours et al 2018;Fuller et al 2019;Goodman et al 2019).…”

Transgenerational effects in offspring of chronically irradiated populations of Drosophila melanogaster after the Chernobyl accident

“…The accident at the Chernobyl Nuclear Power Plant (NPP) in April 1986 has resulted in the contamination of the environment with large amounts of radioactive products. In the postaccident period, researchers have collected a vast amount of scientific information on the impact of hazardous emissions on organisms (Zainullin et al 1992a, 1992b; Møller 2002; Brenner et al 2003; Geras'kin et al 2008; Kozeretska et al 2008; Taskaev et al 2010; Aghajanyan et al 2011; Gudkov et al 2011; Møller et al 2012; Garnier‐Laplace et al 2013; Gaschak et al 2013; Taskaev et al 2016; Bonisoli‐Alquati et al 2018; Omar‐Nazir et al 2018; Goodman et al 2019; Hancock et al 2019a, 2019b; Beresford et al 2020a, 2020b). In particular, changes in the abundance and composition of species, phenotypic aberrations in animals, an increase in the level of cytogenetic disorders in peripheral blood cells, an increase in the incidence of thyroid and lymph cancers in humans have been reported (Zainullin et al 1992a; Møller 2002; Brenner et al 2003; Møller et al 2012).…”