Submerged peatlands – carbon store or carbon source?

Shallow marine sediments play a vital role in regulating climate change by accumulating and burying carbon for up to millions of years – if left undisturbed.  However, fundamental uncertainties remain as too the amount of carbon buried deeper (>10 cm) below the seabed and what happens if it is disturbed. The seabed is being developed for renewable energy and communication at an exponential rate, which may threaten these previously unaccounted for deeper marine carbon stores, risking carbon loss and transformation into greenhouse gases. But we just don’t know…and we’d like an exciting, motivated PhD student to join our team to find out!  Utilising geochemical techniques this PhD project will help to ensure the future renewable energy developments are a sustainable solution to the climate crisis.

Background

During the last ice age, when sea levels were lower, what is now the southern North Sea comprised of extensive terrestrial peatlands (Eaton et al., 2024). As the ice sheets melted, sea level rose, submerging this landscape to become the modern North Sea. Recent research at the University of Leeds has shown these now submerged peatlands contain organic carbon concentrations 30-40 times higher than the shallow marine sediments included in current marine sedimentary carbon inventories. However, these submarine peatlands are omitted from carbon budgets, their roles in carbon cycling and storage are not understood and their vulnerability to environmental change and human activities is unknown.  Human disturbance (for example by offshore windfarm developments) may threaten these previously unaccounted for carbon stores, risking carbon loss and transformation into greenhouse gases. Therefore, it is critical to quantify and assess the vulnerability of these submerged organic carbon stocks as part of efforts to help stabilise global climate and understand their role as climate stores and potential risk as a carbon source.  You can watch lead supervisor, Natasha, give a short presentation on the topic, here.

Objectives

In this project, you will work with leading scientists in the School of Earth and Environment and School of Geography at the University of Leeds, as well as the Universities of Bonn and St Andrews, and project partner Cefas, to understand the carbon in now submerged peatlands.  The supervisory team and Cefas have a wealth of expertise working on Quaternary landscapes in the North Sea region, the analysis of carbon in marine sediments and providing advice on blue carbon to UK policymakers. Specific objectives will be developed in collaboration with the student and Cefas and include, but are not limited to:

• Characterisation of submarine peat and the surrounding “background sediment” from existing core material. Bulk organic and inorganic geochemistry (for example: CNS pyrolysis, stable isotope, thermogravimetric analysis, Rock-Eval pyrolysis XRF, XRD, pyrolysis GC-MS, FTIR) as well as sedimentology (grain size analysis, description of sedimentary structures, thicknesses etc) may be used to quantify the carbon, understand its reactivity and the processes the governed the peat formation.
• Application of radiocarbon dating to constrain the date that the peat developed at each location, to establish a palaeo-environmental framework and depositional history for the different submarine peat settings based on geochemical and sedimentological data.
• Calculation, based on sediment cores as well as existing geophysical data, to develop a 3D volume, and a carbon and sulphur budget for the analysed peat layers across the entire study area.

Potential for high-impact outcomes

The results of this work will have multiple scientific outcomes, with interdisciplinary reach for the geoscience, carbon valuation, marine management and hazard-and-risk research communities. Potential high-impact outcomes of the work include:

• Improved understanding of the composition, biogeochemical processes within, and vulnerability to future degradation, of submarine peat carbon stores;
• Assessment of the vulnerability of peat carbon stores to future anthropogenic and environmental changes, from which to inform marine management strategies;
• Provide carbon stock and vulnerability estimates that will feed into policy (such as ecosystem service valuation and economic assessments) via Cefas, at national and international levels.

There is an increasing amount of offshore core material and geophysical data becoming available for analysis and growing interest in blue carbon and marine management; as result, this PhD could provide the springboard for many further opportunities working in these areas. This project aligns to many NERC research priorities including climate and climate change, geosciences (e.g., Quaternary science), geochemistry, terrestrial and freshwater environments (e.g., Earth system processes and ecosystem-scale processes).  This is an exciting opportunity for Quaternary landscape research and geochemistry to feed directly into policy and environmental decision making.

Training, partners and wider research group

This research project will build upon collaboration between the University of Leeds, the University of Bonn (Prof Christian März), University of St Andrews (Dr Craig Smeaton) and Cefas, as well as existing research relationships with North Sea partners including the Dutch Geological Survey (TNO), Utrecht University, Deltares, Flanders Marine Institute (VLIZ) and BGR. The successful candidate will have access to our extensive world-leading geochemistry laboratories within the Schools of Earth and Environment and Geography at Leeds, and University of Bonn, and benefit from networking opportunities through water@Leeds, Geosolutions Leeds and peatland research groups in the Faculty of Environment. University of Leeds lead supervisors, Barlow and Woulds, put work-life balance and student-led development at the forefront. The welcoming and collegiate atmosphere allows students to explore a wide range of research activities as well as being an in encouraging and nurturing workplace environment.

Project partner Cefas will provide the student the chance to be embedded into a policy-driven science environment and feed their work directly into complementary Cefas research and development on subtidal sedimentary organic carbon (stocks, characteristics, management) and marine natural capital (carbon mapping, pressure-vulnerability relationships, management scenarios). The successful candidate will also have access to a broad spectrum of training workshops facilitated by the YES-DTN at the University of Leeds.

Student profile

The ideal candidate will have a background in geosciences or chemistry, with a relevant degree e.g. Geography, Environmental Science, Oceanography, Geology or Chemistry. A keen interest in laboratory work, geochemistry and environmental change is important.

Relevant publications by supervisory team

• Eaton S, Barlow NLM, Hodgson DM, Mellett CL, Emery AR. (2024). Landscape evolution during Holocene transgression of a mid‐latitude low‐relief coastal plain: The southern North Sea. Earth Surface Processes and Landforms. 3139-3157 49.10 https://doi.org/10.1002/esp.5880
• Graves, C. A., et al. (2022). Sedimentary carbon on the continental shelf: Emerging capabilities and research priorities for Blue Carbon. Frontiers in Marine Science 9:926215 https://doi.org/10.3389/fmars.2022.926215
• März C, Butler PG, Carter GDO and Verhagen ITE (2021) Editorial: The Marine Carbon Cycle: From Ancient Storage to Future Challenges. Frontiers in Earth Science 9:748701. https://10.3389/feart.2021.748701
• Smeaton C, Garrett E, Koot MB, Ladd CJT, Miller LC, McMahon L, Foster B, Barlow NLM, Blake W, Gehrels WR, Skov MW, Austin WEN. (2024). Organic carbon accumulation in British saltmarshes. Science of The Total Environment. 926 https://doi.org/10.1016/j.scitotenv.2024.172104
• Woulds, C., Bell, J.B., Glover, A.G., Bouillon, S. and Brown, L.S., (2020). Benthic carbon fixation and cycling in diffuse hydrothermal and background sediments in the Bransfield Strait, Antarctica. Biogeosciences, 17(1), pp.1-12. https://doi.org/10.5194/bg-17-1-2020