Assessing the Impact of Radiation Exposure on Parasite Infection Susceptibility in Bumblebees in the Chernobyl Exclusion Zone

Ionising radiation is damaging to organisms. These effects are relatively well characterised for humans, but knowledge of how wildlife is affected by exposure to radiologically contaminated environments is comparatively sparse. Major uncertainty surrounds the dose rate thresholds necessary to trigger different forms of biological damage, cause fitness loss in the wild and disrupt ecosystems. Research to clarify this uncertainty sheds light on fundamental biological processes, provides assessment of the ecological impacts of radiological contamination on wildlife and provides the evidence base for the monitoring frameworks governing regulated releases of radionuclides into the environment from industrial, research and medical sources.

Much recent research on this topic has focussed on the Chernobyl exclusion zone, established to restrict human access to the most radiologically contaminated environments after the Chernobyl nuclear accident in 1986. This work has generated major controversy: using contrasting methods and study organisms, some results suggest wildlife suffers minimal or no consequences from current radiation levels, whilst other data indicate substantial deleterious effects at dose rates that are not elevated far above background. Resolving which of these perspectives is correct is a major aim of current investigations.

This PhD project builds on our research over the last 2.5 years that has combined fieldwork in the Chernobyl Exclusion Zone and low dose chronic laboratory exposures to determine the impact of


ionizing radiation on invertebrates. Our recent data from the field and the lab suggests that radiation exposure drives fitness loss in bumblebees at dose rates significantly lower than those previously thought to be damaging. We studied infection by the common bumblebee gut parasite, Crithidia bombi. Our work indicates that these effects of radiation are in part mediated by elevated parasite infection susceptibility under conditions of radiological contamination.

This PhD aims to investigate the impacts of radiation exposure on infection resistance, focussing principally on bumblebees. It will combine field work in the Chernobyl exclusion zone with laboratory work at Stirling University in collaboration with CEH Lancaster.

The precise objectives of this PhD are flexible and could be tailored around the interests and expertise of the applicant. The following outline represents one potential integrated programme of research.

Research Questions:
(1) How is the impact of radiation exposure on bumblebee parasite susceptibility and infection virulence impacted by other environmental stressors?
(2) To what extent is elevated parasite susceptibility following bumblebee radiation exposure driven by impaired ability to induce an immune response?
(3) Are changes in infection dynamics following radiation exposure influenced by changes in parasite characteristics?
(4) To what extent does radiation exposure also increase susceptibility to bumblebee infections other than C. bombi, including other gut parasites, ectoparasites and viral infections.
(5) Do other insects also suffer impaired infection defence following radiation exposure?