CR2025_53 Pathogen on the Rise: Investigating Crayfish Plague (Aphanomyces astaci) Dynamics and Climate Change Impacts on Crayfish in UK Freshwaters

Lead Supervisor: Soon Gweon, Department of Ecology and Evolutionary Biology, University of Reading

Email: h.s.gweon@reading.ac.uk

Co-supervisors: Lindsay Newbold, UK Centre for Ecology and Hydrology; Martin Moore, Loddon Fisheries & Conservation Consultative.

As keystone species and ecosystem engineers, crayfish are among the most ecologically significant organisms in freshwater ecosystems, shaping habitats, influencing biodiversity, and impacting ecological processes. The decline of native European crayfish species in the UK and wider Europe presents a serious conservation challenge, largely due to the invasion of the fungal-like pathogen Aphanomyces astaci, or “crayfish plague”. Introduced primarily by the invasive signal crayfish (Pacifastacus leniusculus), which can asymptomatically host the pathogen, A. astaci has spread rapidly across UK waterways, devastating native white-clawed crayfish populations. This PhD project will focus on understanding the dynamics of A. astaci infection within the UK, its impact on both native and invasive crayfish species, and the broader implications of climate change on pathogen spread and host-pathogen interactions.

The project will develop a comprehensive understanding of A. astaci and its strains in UK aquatic ecosystems through a molecular-based survey of the pathogen, its invasive host, and affected native crayfish populations. These surveys will assess the geographic and temporal spread of A. astaci, identifying potential infection hotspots and regions where native populations are at the highest risk. Establishing sensitive and specific qPCR assays will not only support the initial survey phase but also ongoing monitoring efforts, enabling effective tracking of A. astaci dynamics over time. A key aspect of the project will be exploring the impact of environmental conditions on A. astaci’s pathogenicity and survivability, particularly under climate change scenarios. Preliminary studies have shown that A. astaci thrives in warmer temperatures and lower oxygen conditions—both of which are expected to increase in UK freshwater systems with climate change. Through controlled laboratory experiments that manipulate temperature, pH, and dissolved oxygen, this research will quantify the fitness response of A. astaci under various environmental stressors. These findings will be crucial for predicting whether climate change may exacerbate or mitigate the pathogen’s impact on crayfish populations, potentially informing future conservation strategies. A novel component of this project involves examining interactions between crayfish plague and common waterborne pollutants and bacterial pathogens. Warmer temperatures may increase susceptibility to secondary pathogens or pollutants; therefore, this research will investigate how co-infections or exposure to environmental contaminants impact the health of both infected and non-infected crayfish. This aspect of the study will involve co-culturing A. astaci with bacterial pathogens and common waterborne pollutants to observe cumulative impacts on pathogen fitness. Such studies may reveal compounding vulnerabilities under climate-altered conditions, offering insights into the future resilience of both crayfish and pathogens in the face of multiple stressors. The project will also explore the development of an in-field lab protocol using Oxford Nanopore’s portable sequencing technology for rapid, on-site monitoring of A. astaci in UK waterways. By enabling near-real-time detection of A. astaci directly from environmental DNA samples, this approach offers a rapid, field-deployable means of detecting pathogen presence. Real-time monitoring could provide early warning for pathogen outbreaks, facilitating rapid biosecurity responses and helping to limit A. astaci’s spread to vulnerable white-clawed crayfish populations. The findings from this research will have direct applications in conservation management. Drawing on insights from molecular surveys, environmental trials, and physiological studies, the project will work in collaboration with Loddon Fisheries & Conservation Consultative to design adaptive management strategies. These may include designating conservation areas based on predicted infection risk, identifying refuges for white-clawed crayfish, or implementing biosecurity measures around high-risk zones. Additionally, the study will provide data-driven recommendations for proactive conservation strategies to mitigate climate change’s impact on A. astaci spread. These strategies might involve promoting habitat refuges that naturally buffer against warming and pollution or fostering genetic resilience in native crayfish populations through selective breeding or reintroduction efforts.

In summary, this PhD proposal outlines a comprehensive investigation into A. astaci infection dynamics in the UK, with an emphasis on the role of environmental conditions and climate change in shaping pathogen-host interactions. By optimising molecular detection methods, studying the environmental drivers of pathogen fitness, and assessing the ecological impacts on native crayfish, this project will contribute to a deeper understanding of freshwater ecosystem health and resilience in the UK. Through collaborative conservation planning and innovative laboratory approaches, this research aims to protect the UK’s native white-clawed crayfish from the growing threat posed by invasive species and global climate change.

Training opportunities: 

The student will gain specialised training through placements with the CASE partner, focusing on freshwater biodiversity monitoring and conservation methods like electrofishing, seine netting and trapping surveys with certifications available through the Institute of Fisheries Management (IFM). They will also receive training in molecular techniques, including eDNA sampling, qPCR assays, and portable sequencing. This partnership will enhance their communication skills, providing opportunities to present research to non-scientific audiences and participate in public outreach, equipping them with essential expertise in both technical skills and effective science communication for conservation. 

Student profile:

The ideal student for this project would have a background in environmental science, ecology, microbiology, or molecular biology, with experience in both field and lab-based research. Key skills include molecular techniques such as qPCR, DNA extraction, and pathogen detection, alongside practical field skills like biodiversity monitoring or eDNA sampling. Familiarity with bioinformatics for genomic data analysis and experience in science communication for outreach purposes would be advantageous. A demonstrated commitment to conservation and adaptability to both independent and collaborative research environments are essential.

Co-Sponsorship details: 

This project will receive a CASE award from Loddon Fisheries & Conservation Consultative.