IAP-24-075

How does climate change impact reindeer populations? Reconstructing Arctic environments using lipid biomarkers in lake sediments.

Herd herbivores are essential components of Arctic ecosystems. They play important roles in sustaining local food webs and maintaining terrestrial ecosystems. Reindeer (Rangifer tarandus) are also integral to Indigenous culture, identity and economies. However, the viability of future herding in the Arctic under current and projected climate change is cause for concern. Historical Rangifer population records collected since the 1960’s provide valuable insights into the species vulnerability and highlight differences in rates of population decline across Fennoscandia (e.g. Finnish sub-Arctic and northern Norway) (Vors and Boyce, 2009). Increased Rangifer mortality rates in Fennoscandia are linked to (1) increased rain-on-snow events that form impenetrable ground surface ice layers, preventing access to vegetation food sources; and (2) competition with other land users and alterations in food web dynamics (e.g., Rosqvist et al., 2022). Regional differences in rates of Rangifer decline are influenced by differences in the timings and magnitudes of changes in environmental conditions such as precipitation, temperature and freezing events (e.g., Mallory and Boyce, 2017). Projected climate warming will increase stress and mortality in Rangifer populations, and the resultant changes in Rangifer herd sizes and distributions will feedback into wide-reaching environmental impacts e.g., disruption of vegetation dynamics and nutrient cycles.

This PhD project aims to assess the regional sustainability of herds and herding practices under environmental changes by developing long-term records of Rangifer population and climate. These records will be developed from naturally accumulating lake sedimentary archives that will be independently dated. The project will use geochemical analyses of newly-collected lake sedimentary archives from the regions in the Scandinavian Arctic to provide multi-proxy evidence for changes in temperature, precipitation, Rangifer herd dynamics, nutrient cycling, and vegetation change.

The specific objectives of the PhD are to:
• Characterise the timings and intensities of reindeer herding from Arctic case study regions and how they have changed over the Holocene
• Reconstruct Holocene climate dynamics in study regions
• Characterise the impacts of reindeer herding on lake nutrient cycling and vegetation change
• Evaluate the role of environment change in shaping Arctic reindeer herding dynamics.

This project uses a variety of different techniques to characterise lake sediment geochemistry and reconstruct past environmental change. Some of these techniques are not commonly taught at undergraduate and/or masters level so the supervisory team will provide full training in all methods. We are looking for a student with interests in palaeoclimate and/or human-animal-environment interactions who enjoys lab work.

The student will have the opportunity to conduct Arctic fieldwork to survey lake study sites, analyse water column physiochemistry and recover Holocene sediment cores from lakes. These sediments will undergo lithostratigraphic analysis using loss-on-ignition (LOI), mineral magnetics and XRF scanning. To assess changes in the timings and intensities of reindeer herding activities the student will date the lake sediments using radiocarbon and use lipid biomarkers (sterols, bile acids) (Prost et al., 2017) to track faecal input into the lake. The student will use leaf wax n-alkanes to reconstruct vegetation changes and hydrogen isotopes to reconstruct past hydroclimate (McClymont, Mackay et al., 2023). Depending on how the project develops there will be opportunities to explore other lipid biomarker analyses to complement the proposed palaeoenvironmental analyses. For example, analyses of GDGTs could be included to reconstruct changes in temperature. There is scope for the successful candidate to shape the direction of the laboratory analyses based on their interests (e.g., the project lends itself well to sedimentary ancient DNA/palaeoecological analyses such as pollen).

The project benefits from working closely with project partners and organic geochemists Dr Darci Rush (Royal Netherlands Institute for Sea Research, NIOZ) and Dr Melissa Berke (University of Notre Dame). There are opportunities for the successful candidate to conduct a placement for training in orbitrap GC-MS analyses in the Netherlands and/or apply for funding to be trained in compound-specific stable isotope analysis in the USA.

Year 1

– Review existing literature on Arctic reindeer herding and long-term environmental change.
– Plan and conduct fieldwork in the Arctic (e.g., Finland and/or Norway) to extract lake sediment cores.
– Start laboratory analysis on sediment cores, which will include sediment descriptions, physical properties analysis (elemental chemistry (XRF) and carbon analysis) and sub-sampling the core for lipid biomarker analyses. Conduct initial radiocarbon dating of the cores.
– Complete first year progression paper to detail the project overview, research questions and methodology

Year 2

– Continue laboratory analysis (lipid biomarkers).
– Complete radiocarbon analysis and produce core chronologies.
– Present initial results at a national conference (e.g., British Organic Geochemistry Society or Quaternary Research Association).
– Write up 1st results paper.

Year 3

– Finalise laboratory work with an opportunity for further analytical training at the Royal Netherlands Institute for Sea Research and/or University of Notre Dame, USA.
– Data analysis and interpretation.
– Present results as an international conference (e.g., International Union for Quaternary Research/International Paleolimnological Association/International Meeting of Organic Geochemistry).
– Write up 2nd results papers and begin overall thesis writeup.

Year 3.5

– Preparation and completion of final chapters of the thesis and 3rd results paper for publication.

This project will develop cross-disciplinary, transferable skills in problem solving, project management, experimental design, data analysis and visualisation and report writing.

High-levels skills will be developed in:
• Field techniques with training in lake surveying and coring.
• Laboratory analyses with full training provided on sediment core logging, radiocarbon dating, XRF scanning and lipid biomarker extraction, processing and analysis at Durham University state-of-the-art research laboratories. The analyses can be shaped to the interest of the successful candidate (e.g. to include sedimentary ancient DNA/palaeoecology) and there is scope to design an international placement at the Royal Netherlands Institute for Sea Research to be trained in state-of-the-art orbitrap GC-MS analysis.
• Computational/statistical analyses with training on computer programming in R for data visualisation and statistical analyses provided at Durham University

The candidate will also benefit from broad skills training provided in-house at Durham (e.g. science communication, thesis writing, writing for grants and publications, presentation skills) via the Geography Department and the award winning Career and Research Development (CAROD) group. Furthermore, a broad range of training in environmental science and science communication is provided within the IAPETUS2 Doctoral Training Partnership. Training requirements of the individual will be identified and met through the development of a personal training plan.

The presence of international collaborators ensures that the student has excellent opportunities to develop a strong multidisciplinary research network. Research skills and awareness of on-going research will be developed through regular participation in Durham’s Physical Geography weekly research group meetings and seminar series, and external national and international conferences to support development as an independent researcher.