Some observations on meaningful and objective inference in radioecological field studies.

Anthropogenic releases of radiation are of ongoing importance for environmental protection, but the radiation doses at which natural systems begin to show effects are controversial. More certainty is required in this area to achieve optimal regulation for radioactive substances. We recently carried out a large survey (268 sampled animals and 20 sites) of the association between environmental radiation exposures and small mammal gut-associated microbiomes (fungal and bacterial) in the Chornobyl Exclusion zone (CEZ). Using individual measurements of total absorbed dose rates and a study design and analyses that accounted for spatial non-independence, we found no, or only limited, association. Watts et al. have criticised our study: for not filtering candidate non-resident components prior to our fungal microbiome analyses, for our qualified speculations on the relative merits of faecal and gut samples, and for the design of our study which they felt lacked sufficient replication. The advantage of filtering non-resident-fungal taxa is not clear and it would not have changed the null (spatially adjusted) association we found between radioactive dose and mycobiome composition because the most discriminatory fungal taxa with regard to dose were non-resident taxa. We maintain that it was legitimate for us to make qualified discussion comments on the differences in results between our faecal and gut microbiome analyses and on the relative merits of these sample types. Most importantly, the criticism of our study design by Watts et al. and the designs and analysis of their recent studies in the CEZ show a misunderstanding of the true nature of independent replication in field studies. Recognising the importance of spatial non-independence is essential in the design and analysis of radioecological field surveys.

Impacts of radiation exposure on the bacterial and fungal microbiome of small mammals in the Chernobyl Exclusion Zone.

Environmental impacts of the 1986 Chernobyl Nuclear Power Plant accident are much debated, but the effects of radiation on host microbiomes have received little attention to date. We present the first analysis of small mammal gut microbiomes from the Chernobyl Exclusion Zone in relation to total absorbed dose rate, including both caecum and faeces samples. We provide novel evidence that host species determines fungal community composition, and that associations between microbiome (both bacterial and fungal) communities and radiation exposure vary between host species. Using ambient versus total weighted absorbed dose rates in analyses produced different results, with the latter more robust for interpreting microbiome changes at the individual level. We found considerable variation between results for faecal and gut samples of bank voles, suggesting faecal samples are not an accurate indicator of gut composition. Associations between radiation exposure and microbiome composition of gut samples were not robust against geographical variation, although we identified families of bacteria (Lachnospiraceae and Muribaculaceae) and fungi (Steccherinaceae and Strophariaceae) in the guts of bank voles that may serve as biomarkers of radiation exposure. Further studies considering a range of small mammal species are needed to establish the robustness of these potential biomarkers.

Education and training in radioecology during the EU-COMET project-successes and suggestions for the future.

The 2014 Strategic Research Agenda (SRA) for Radioecology identified the key challenge in education and training (E&T) as being 'to maintain and develop a skilled workforce in Europe and world-wide, through university candidates and professionals trained within radioecology' since 'scientific research in radioecology and application of that knowledge … requires scientists and workers with adequate competence and appropriate skills.' Radioecology is a multidisciplinary science and E&T is needed by both students and professionals within research, industry and radiation protection. In order to address these needs, the EU COMET project has developed an E&T web platform and arranged a number of field courses, training courses, PhD and MSc courses, refresher courses and workshops, drawing on the COMET consortium to assemble relevant experts. In addition, COMET has been engaged in discussions with stakeholders for more long-term solutions to maintain the sustainability of radioecology E&T after the end of the project. Despite much progress in some areas, many of the challenges outlined in the 2014 SRA remain, mainly due to the lack of sustainable dedicated funding. Future plans within the ALLIANCE radioecology platform and the CONCERT-European Joint Programme for the Integration of Radiation Protection Research must urgently address this lack of sustainability if radioecological competence is to be maintained in Europe.

Radiological dose rates to marine fish from the Fukushima Daiichi accident: the first three years across the North Pacific.

A more complete record is emerging of radionuclide measurements in fish tissue, sediment, and seawater samples from near the Fukushima Daiichi Nuclear Power Plant (FDNPP) and across the Pacific Ocean. Our analysis of publicly available data indicates the dose rates to the most impacted fish species near the FDNPP (median 1.1 mGy d(-1), 2012-2014 data) have remained above benchmark levels for potential dose effects at least three years longer than was indicated by previous, data-limited evaluations. Dose rates from (134,137)Cs were highest in demersal species with sediment-associated food chains and feeding behaviors. In addition to (134,137)Cs, the radionuclide (90)Sr was estimated to contribute up to approximately one-half of the total 2013 dose rate to fish near the FDNPP. Mesopelagic fish 100-200 km east of the FDNPP, coastal fish in the Aleutian Islands (3300 km), and trans-Pacific migratory species all had increased dose rates as a consequence of the FDNPP accident, but their total dose rates remained dominated by background radionuclides. A hypothetical human consumer of 50 kg of fish, gathered 3 km from the FDNPP in 2013, would have received a total committed effective dose of approximately 0.95 mSv a(-1) from combined FDNPP and ambient radionuclides, of which 0.13 mSv a(-1) (14%) was solely from the FDNPP radionuclides and below the 1 mSv a(-1) benchmark for public exposure.

Relationships between radiation, wildfire and the soil microbial communities in the Chornobyl Exclusion Zone.

There is considerable uncertainty regarding radiation's effects on biodiversity in natural complex ecosystems typically subjected to multiple environmental disturbances and stresses. In this study we characterised the relationships between soil microbial communities and estimated total absorbed dose rates to bacteria, grassy vegetation and trees in the Red Forest region of the Chornobyl Exclusion Zone. Samples were taken from sites of contrasting ecological histories and along burn and no burn areas following a wildfire. Estimated total absorbed dose rates to bacteria reached levels one order of magnitude higher than those known to affect bacteria in laboratory studies. Sites with harsher ecological conditions, notably acidic pH and low soil moisture, tended to have higher radiation contamination levels. No relationship between the effects of fire and radiation were observed. Microbial groups that correlated with high radiation sites were mostly classified to taxa associated with high environmental stress habitats or stress resistance traits. Distance-based linear models and co-occurrence analysis revealed that the effects of radiation on the soil microbiome were minimal. Hence, the association between high radiation sites and specific microbial groups is more likely a result of the harsher ecological conditions in these sites, rather than due to radiation itself. In this study, we provide a starting point for understanding the relationship between soil microbial communities and estimated total absorbed radiation dose rates to different components of an ecosystem highly contaminated with radiation. Our results suggest that soil microbiomes adapted to natural soil conditions are more likely to be resistant to ionising radiation than expected from laboratory studies, which demonstrates the importance of assessing the impact of ionising radiation on soil microbial communities under field conditions.

Current ionising radiation doses in the Chernobyl Exclusion Zone do not directly impact on soil biological activity.

Although soil organisms are essential for ecosystem function, the impacts of radiation on soil biological activity at highly contaminated sites has been relatively poorly studied. In April-May 2016, we conducted the first largescale deployment of bait lamina to estimate soil organism (largely soil invertebrate) feeding activity in situ at study plots in the Chernobyl Exclusion Zone (CEZ). Across our 53 study plots, estimated weighted absorbed dose rates to soil organisms ranged from 0.7 µGy h-1 to 1753 µGy h-1. There was no significant relationship between soil organism feeding activity and estimated weighted absorbed dose rate. Soil biological activity did show significant relationships with soil moisture content, bulk density (used as a proxy for soil organic matter) and pH. At plots in the Red Forest (an area of coniferous plantation where trees died because of high radiation exposure in 1986) soil biological activity was low compared to plots elsewhere in the CEZ. It is possible that the lower biological activity observed in the Red Forest is a residual consequence of what was in effect an acute high exposure to radiation in 1986.

Radiological risk assessment to marine biota from exposure to NORM from a decommissioned offshore oil and gas pipeline.

Scale residues can accumulate on the interior surfaces of subsea petroleum pipes and may incorporate naturally occurring radioactive materials (NORM). The persistent nature of 'NORM scale' may result in a radiological dose to the organisms living on or near intact pipelines. Following a scenario of in-situ decommissioning of a subsea pipeline, marine organisms occupying the exteriors or interiors of petroleum structures may have close contact with the scale or other NORM-associated contaminated substances and suffer subsequent radiological effects. This case study used radiological dose modelling software, including the ERICA Tool (v2.0), MicroShield® Pro and mathematical equations, to estimate the likely radiological doses and risks of effects from NORM-contaminated scale to marine biota from a decommissioned offshore oil and gas pipeline. Using activity concentrations of NORM (226Ra, 210Po, 210Pb, 228Ra, 228Th) from a subsea pipeline from Australia, environmental realistic exposure scenarios including radiological exposures from both an intact pipe (external only; accounting for radiation shielding by a cylindrical carbon steel pipe) and a decommissioned pipeline with corrosive breakthrough (resulting in both internal and external radiological exposure) were simulated to estimate doses to model marine organisms. Predicted dose rates for both the external only exposure (ranging from 26 µGy/h to 33 µGy/h) and a corroded pipeline (ranging from 300 µGy/h to 16,000 µGy/h) exceeded screening levels for radiological doses to environmental receptors. The study highlighted the importance of using scale-specific solubility data (i.e., Kd) values for individual NORM radionuclides for ERICA assessments. This study provides an approach for conducting marine organism dose assessments for NORM-contaminated subsea pipelines and highlights scientific gaps required to undertake risk assessments necessary to inform infrastructure decommissioning planning.

Best practices for predictions of radionuclide activity concentrations and total absorbed dose rates to freshwater organisms exposed to uranium mining/milling.

Predictions of radionuclide dose rates to freshwater organisms can be used to evaluate the radiological environmental impacts of releases from uranium mining and milling projects. These predictions help inform decisions on the implementation of mitigation measures. The objective of this study was to identify how dose rate modelling could be improved to reduce uncertainty in predictions to non-human biota. For this purpose, we modelled the activity concentrations of 210Pb, 210Po, 226Ra, 230Th, and 238U downstream of uranium mines and mills in northern Saskatchewan, Canada, together with associated weighted absorbed dose rates for a freshwater food chain using measured activity concentrations in water and sediments. Differences in predictions of radionuclide activity concentrations occurred mainly from the different default partition coefficient and concentration ratio values from one model to another and including all or only some 238U decay daughters in the dose rate assessments. Consequently, we recommend a standardized best-practice approach to calculate weighted absorbed dose rates to freshwater biota whether a facility is at the planning, operating or decommissioned stage. At the initial planning stage, the best-practice approach recommend using conservative site-specific baseline activity concentrations in water, sediments and organisms and predict conservative incremental activity concentrations in these media by selecting concentration ratios based on species similarity and similar water quality conditions to reduce the uncertainty in dose rate calculations. At the operating and decommissioned stages, the best-practice approach recommends relying on measured activity concentrations in water, sediment, fish tissue and whole-body of small organisms to further reduce uncertainty in dose rate estimates. This approach would allow for more realistic but still conservative dose assessments when evaluating impacts from uranium mining projects and making decision on adequate controls of releases.

Adverse outcome pathways (AOPs) for radiation-induced reproductive effects in environmental species: state of science and identification of a consensus AOP network.

BACKGROUND: Reproductive effects of ionizing radiation in organisms have been observed under laboratory and field conditions. Such assessments often rely on associations between exposure and effects, and thus lacking a detailed mechanistic understanding of causality between effects occurring at different levels of biological organization. The Adverse Outcome Pathway (AOP), a conceptual knowledge framework to capture, organize, evaluate and visualize the scientific knowledge of relevant toxicological effects, has the potential to evaluate the causal relationships between molecular, cellular, individual, and population effects. This paper presents the first development of a set of consensus AOPs for reproductive effects of ionizing radiation in wildlife. This work was performed by a group of experts formed during a workshop organized jointly by the Multidisciplinary European Low Dose Initiative (MELODI) and the European Radioecology Alliance (ALLIANCE) associations to present the AOP approach and tools. The work presents a series of taxon-specific case studies that were used to identify relevant empirical evidence, identify common AOP components and propose a set of consensus AOPs that could be organized into an AOP network with broader taxonomic applicability. CONCLUSION: Expert consultation led to the identification of key biological events and description of causal linkages between ionizing radiation, reproductive impairment and reduction in population fitness. The study characterized the knowledge domain of taxon-specific AOPs, identified knowledge gaps pertinent to reproductive-relevant AOP development and reflected on how AOPs could assist applications in radiation (radioecological) research, environmental health assessment, and radiological protection. Future advancement and consolidation of the AOPs is planned to include structured weight of evidence considerations, formalized review and critical assessment of the empirical evidence prior to formal submission and review by the OECD sponsored AOP development program.

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

The objective of this paper is to present the results of discussions at a workshop held as part of the International Congress of Radiation Research (Environmental Health stream) in Manchester UK, 2019. The main objective of the workshop was to provide a platform for radioecologists to engage with radiobiologists to address major questions around developing an Ecosystem approach in radioecology and radiation protection of the environment. The aim was to establish a critical framework to guide research that would permit integration of a pan-ecosystem approach into radiation protection guidelines and regulation for the environment. The conclusions were that the interaction between radioecologists and radiobiologists is useful in particular in addressing field versus laboratory issues where there are issues and challenges in designing good field experiments and a need to cross validate field data against laboratory data and vice versa. Other main conclusions were that there is a need to appreciate wider issues in ecology to design good approaches for an ecosystems approach in radioecology and that with the capture of 'Big Data', novel tools such as machine learning can now be applied to help with the complex issues involved in developing an ecosystem approach.

Radiocesium concentration ratios and radiation dose to wild rodents in Fukushima Prefecture.

Radiocesium was dispersed from the Fukushima Dai-ichi disaster in March 2011, causing comparatively high radioactive contamination in nearby environments. Radionuclide concentrations in wild rodents (Apodemus argenteus, and Apodemus speciosus) within these areas were monitored from 2012 to 2016. However, whole-organism to soil transfer parameters (i.e., concentration ratio, CRwo-soil) for wild rodents at Fukushima were not determined and hence were lacking from the international transfer databases. We augmented the 2012-2016 data by collecting soil activity concentrations (Bq kg-1, dry mass) from five rodent sampling sites in Fukushima Prefecture, and developed corresponding CRwo-soil values for radiocesium (134Cs and 137Cs) based on rodent radioactivity concentrations (Bq kg-1, fresh mass). The CRwo-soil were added to the Wildlife Transfer Database (WTD; http://www.wildlifetransferdatabase.org/), supporting the development of the International Commission on Radiological Protection's (ICRP) environmental protection framework, and increasing the WTD from 84 to 477 entries for cesium and Muridae ('Reference Rat'). Significant variation occurred in CRwo-soil values between study sites within Fukushima Prefecture. The geometric mean CRwo-soil, in this paper, was higher than that reported for Muridae species for Chernobyl. Radiocaesium absorbed dose rates were also estimated for wild rodents inhabiting the five Fukushima study sites and ranged from 1.3 to 33 µGy h-1. Absorbed dose rates decreased by a factor of two from 2012 to 2016. Dose rates in highly contaminated areas were within the ICRP derived consideration reference level for Reference Rat (0.1-1 mGy d-1), suggesting the possible occurrence of deleterious effects and need for radiological effect studies in the Fukushima area.

Wildfires in the Chornobyl exclusion zone-Risks and consequences.

Following the 1986 Chornobyl accident, an area approaching 5000 km2 surrounding the nuclear plant was abandoned, creating the Chornobyl exclusion zone (CEZ). Although this area likely contains the most radioactive terrestrial ecosystem on earth, the absence of humans and associated activities for nearly 35 years since the accident has resulted in increases in wildlife numbers. Both the Belarussian and Ukrainian components of the CEZ are now designated as nature reserves; together they form one of Europe's largest protected areas and have been described as an iconic example of rewilding. Forests and former agricultural land (now scrub) dominate the CEZ and wildfires are an annual event. In April 2020, the CEZ suffered its most widespread fires to date when greater than 800 km2 of the 2600 km2 Ukrainian portion of the CEZ was burnt. Large-scale fires in the CEZ have implications for wildlife, as they do elsewhere, but they also pose additional radioecological and radiological protection questions. We discuss the implications of wildfires in the CEZ, considering effects on wildlife and changes in radionuclide mobility. We also demonstrate that the risk to firefighters and the wider public from the inhalation of radionuclides in smoke resulting from fires in the CEZ is likely to be low. However, further experimental and modeling work to evaluate potential doses to firefighters from inhaled radioactive particles would be valuable, not least for reassurance purposes. Integr Environ Assess Manag 2021;17:1141-1150 © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

An updated strategic research agenda for the integration of radioecology in the european radiation protection research.

The ALLIANCE Strategic Research Agenda (SRA) for radioecology is a living document that defines a long-term vision (20 years) of the needs for, and implementation of, research in radioecology in Europe. The initial SRA, published in 2012, included consultation with a wide range of stakeholders (Hinton et al., 2013). This revised version is an update of the research strategy for identified research challenges, and includes a strategy to maintain and develop the associated required capacities for workforce (education and training) and research infrastructures and capabilities. Beyond radioecology, this SRA update constitutes a contribution to the implementation of a Joint Roadmap for radiation protection research in Europe (CONCERT, 2019a). This roadmap, established under the H2020 European Joint Programme CONCERT, provides a common and shared vision for radiation protection research, priority areas and strategic objectives for collaboration within a European radiation protection research programme to 2030 and beyond. Considering the advances made since the first SRA, this updated version presents research challenges and priorities including identified scientific issues that, when successfully resolved, have the potential to impact substantially and strengthen the system and/or practice of the overall radiation protection (game changers) in radioecology with regard to their integration into the global vision of European research in radiation protection. An additional aim of this paper is to encourage contribution from research communities, end users, decision makers and other stakeholders in the evaluation, further advancement and accomplishment of the identified priorities.

Radionuclide transfer to reptiles.

Reptiles are an important, and often protected, component of many ecosystems but have rarely been fully considered within ecological risk assessments (ERA) due to a paucity of data on contaminant uptake and effects. This paper presents a meta-analysis of literature-derived environmental media (soil and water) to whole-body concentration ratios (CRs) for predicting the transfer of 35 elements (Am, As, B, Ba, Ca, Cd, Ce, Cm, Co, Cr, Cs, Cu, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Po, Pu, Ra, Rb, Sb, Se, Sr, Th, U, V, Y, Zn, Zr) to reptiles in freshwater ecosystems and 15 elements (Am, C, Cs, Cu, K, Mn, Ni, Pb, Po, Pu, Sr, Tc, Th, U, Zn) to reptiles in terrestrial ecosystems. These reptile CRs are compared with CRs for other vertebrate groups. Tissue distribution data are also presented along with data on the fractional mass of bone, kidney, liver and muscle in reptiles. Although the data were originally collected for use in radiation dose assessments, many of the CR data presented in this paper will also be useful for chemical ERA and for the assessments of dietary transfer in humans for whom reptiles constitute an important component of the diet, such as in Australian aboriginal communities.

Whole-body to tissue concentration ratios for use in biota dose assessments for animals.

Environmental monitoring programs often measure contaminant concentrations in animal tissues consumed by humans (e.g., muscle). By comparison, demonstration of the protection of biota from the potential effects of radionuclides involves a comparison of whole-body doses to radiological dose benchmarks. Consequently, methods for deriving whole-body concentration ratios based on tissue-specific data are required to make best use of the available information. This paper provides a series of look-up tables with whole-body:tissue-specific concentration ratios for non-human biota. Focus was placed on relatively broad animal categories (including molluscs, crustaceans, freshwater fishes, marine fishes, amphibians, reptiles, birds and mammals) and commonly measured tissues (specifically, bone, muscle, liver and kidney). Depending upon organism, whole-body to tissue concentration ratios were derived for between 12 and 47 elements. The whole-body to tissue concentration ratios can be used to estimate whole-body concentrations from tissue-specific measurements. However, we recommend that any given whole-body to tissue concentration ratio should not be used if the value falls between 0.75 and 1.5. Instead, a value of one should be assumed.

Estimating radiological exposure of wildlife in the field.

The assessment of the ecological impact due to radionuclides at contaminated sites requires estimation of the exposure of wildlife, in order to correlate radiation dose with known radiological effects. The robust interpretation of field data requires consideration of possible confounding effects (e.g., from the tsunami at Fukushima) and an accurate and relevant quantification of radiation doses to biota. Generally, in field studies the exposure of fauna and flora has often been characterised as measurements of the ambient dose rate or activity concentrations in some components of the environment. The use of such data does not allow the establishment of a robust dose-effect relationship for wildlife exposed to ionising radiation in the field. Effects of exposure to radioactivity depend on the total amount of energy deposited into exposed organisms, which is estimated by adding doses (or dose rates) for all radionuclides and exposure pathways. Realistic dose estimation needs to reflect the entire story of the organisms of interest during their whole exposure period. The process of identifying and collecting all the related information should allow the "W" questions (Which organisms are exposed, Where, When and hoW) to be answered. Some parameters are well known to influence dose (rate): the organism life stage, its ecological characteristics (e.g. habitat, behaviour), the source term properties (e.g. discharging facility, nature of radiation), etc. The closer the collated data are to the ideal data set, the more accurate and realistic the dose (rate) assessment will be. This means characterising each exposure pathway (internal and external), the activity concentration in each exposure source, the time each organism spends in a given place, as well as the associated dose. In this paper the process of data collation in view of dose reconstruction is illustrated for Japanese birds exposed to radioactive deposition following the Fukushima accident. With respect to the Chernobyl Exclusion Zone we will also consider variability under field conditions, availability of relevant datasets and options for better estimating internal and external doses received by wildlife.

Fit-for-purpose modelling of radiocaesium soil-to-plant transfer for nuclear emergencies: a review.

Numerous radioecological models have been developed to predict radionuclides transfer from contaminated soils to the food chain, which is an essential step in preparing and responding to nuclear emergencies. However, the lessons learned from applying these models to predict radiocaesium (RCs) soil-to-plant transfer following the Fukushima accident in 2011 renewed interest in RCs transfer modelling. To help guide and prioritise further research in relation to modelling RCs transfer in terrestrial environments, we reviewed existing models focussing on transfer to food crops and animal fodders. To facilitate the review process, we categorised existing RCs soil-to-plant transfer models into empirical, semi-mechanistic and mechanistic, though several models cross the boundaries between these categories. The empirical approach predicts RCs transfer to plants based on total RCs concentration in soil and an empirical transfer factor. The semi-mechanistic approach takes into account the influence of soil characteristics such as clay and exchangeable potassium content on RCs transfer. It also uses 'bioavailable' rather than total RCs in soil. The mechanistic approach considers the physical and chemical processes that control RCs distribution and uptake in soil-plant systems including transport in the root zone and root absorption kinetics. Each of these modelling approaches has its advantages and disadvantages. The empirical approach is simple and requires two inputs, but it is often associated with considerably uncertainty due to the large variability in the transfer factor. The semi-mechanistic approach factorises more soil and plant parameters than the empirical approach; therefore, it is applicable to a wider range of environmental conditions. The mechanistic approach is instrumental in understanding RCs mobility and transfer in soil-plant systems; it also helps to identify influential soil and plant parameters. However, the comlexity and the large amount of specific parameters make this approach impractical for nuclear emergency preparedness and response purposes. We propose that the semi-mechanistic approach is sufficiently robust and practical, hence more fit for the purpose of planning and responding to nuclear emergencies compared with the empirical and mechanistic approaches. We recommend further work to extend the applicability of the semi-mechanistic approach to a wide range of plants and soils.

Measuring the radiation exposure of Norwegian reindeer under field conditions.

Models and approaches have been developed to predict radiation exposure of wildlife under field conditions. However, there have been few attempts to directly measure radiation exposure of wildlife in the field and confirm the doses predicted by models. This is a potential issue for stakeholder acceptance of modelling-based assessments. Here is presented a comprehensive study comparing the results of different dosimeters fitted to free-ranging reindeer inhabiting an area that received comparatively high radiocaesium deposition from the 1986 Chernobyl accident. The external dose of reindeer was measured using the four dosimeter types in aluminium box mounted on the GPS collar. The measurements were compared with two model predictions: (i) external dose to reindeer across the entire range area of the herd; and (ii) external doses of individual reindeer predicted using GPS tracking data to determine locations. It was found that although significant differences between the estimates of the various dosimeters were found these were small with no practical implication. Also, the mean predicted external doses using the GPS tracking data were not significantly different to estimates from two of the four passive dosimeter results. The average external dose predicted across the herd area was significantly lower than doses recorded by the dosimeters and also estimates using GPS data to determine reindeer location (and hence exposure). For 137Cs the average external dose from the GPS tracking data was about twice that predicted across the herd area, because collared animals favoured the more contaminated area of the study site. This suggests that in some circumstances the assumption of averaging contamination over an assumed home range within assessments may be inadequate though this would need to be balanced against other uncertainties. Natural radiation was the greatest contribution to reindeer exposure and a function of the high altitude.

Genetic, epigenetic and microbiome characterisation of an earthworm species (Octolasion lacteum) along a radiation exposure gradient at Chernobyl.

The effects of exposure to different levels of ionising radiation were assessed on the genetic, epigenetic and microbiome characteristics of the "hologenome" of earthworms collected at sites within the Chernobyl exclusion zone (CEZ). The earthworms Aporrectodea caliginosa (Savigny, 1826) and Octolasion lacteum (Örley, 1881) were the two species that were most frequently found at visited sites, however, only O. lacteum was present at sufficient number across different exposure levels to enable comparative hologenome analysis. The identification of morphotype O. lacteum as a probable single clade was established using a combination of mitochondrial (cytochrome oxidase I) and nuclear genome (Amplified Fragment Length Polymorphism (AFLP) using MspI loci). No clear site associated differences in population genetic structure was found between populations using the AFLP marker loci. Further, no relationship between ionising radiation exposure levels and the percentage of methylated loci or pattern of distribution of DNA methylation marks was found. Microbiome structure was clearly site dependent, with gut microbiome community structure and diversity being systematically associated with calculated site-specific earthworm dose rates. There was, however, also co-correlation between earthworm dose rates and other soil properties, notably soil pH; a property known to affect soil bacterial community structure. Such co-correlation means that it is not possible to attribute microbiome changes unequivocally to radionuclide exposure. A better understanding of the relationship between radionuclide exposure soil properties and their interactions on bacterial microbiome community response is, therefore, needed to establish whether these the observed microbiome changes are attributed directly to radiation exposure, other soil properties or to an interaction between multiple variables at sites within the CEZ.