Where did all the Carbon go? Understanding and predicting carbon inventories in coarse sediments

Dr Charlie Thompson, Dr Ruth Parker (Cefas), Dr John Aldridge (Cefas), Prof Gary Fones (University of Portsmouth)

Marine environments absorb ~25% of global CO2 emissions annually.  ‘Blue Carbon’ (BC) habitats can provide long term storage of this CO2, potentially mitigating against climate change. However, there is significant uncertainty surrounding carbon stocks, sources and burial in marine habitats. This is especially true for sand and gravel dominated areas, which comprise a significant stock of carbon in shelf-sea environments (Diesing et al., 2017).

Sands and gravels make up a substantial proportion of shelf sea sediments. Highly permeable, pore-water flows through their upper layers allowing them to act as bioreactors, rapidly exchanging nutrients and carbon between the bed and water column (e.g. Huettel, 2014). However, our understanding of what controls these biogeochemical processes is lacking. As such, many ecosystem models (used to understand the state of health of marine ecosystems and resources in a changing environment) neglect pore water transport assuming only molecular diffusion controls transport processes. We are not accurately modelling biogeochemical cycles on shelf seas, making it difficult to predict BC stocks and fluxes and preventing sustainable management of these potential storage habitats.

This coupled observational and modelling studentship will fundamentally improve existing biogeochemical models to allow more representative BC stock predictions, now and in the future.


The studentship will combine observational, experimental and modelling techniques, including:

  • Characterization of fundamental seabed parameters. Sediments will be collected using cores designed to minimise bed disturbance, and sub-sampled before analysis using a range of laboratory techniques.
  • Experimental flume analysis of biogeochemical processes & carbon cycling. A suite of laboratory and ship-based annular flumes will be used to induce flows typical of those on the shelf across remolded or cored sediment beds. Water and sediment sampling will be used to determine geotechnical properties, and key biogeochemical concentrations, rates and fluxes.
  • Modelling of these processes on sediment biogeochemistry (with an emphasis on Oxygen and organic Carbon), and one or more scales:
    • at small scales (COMSOL and/or R based: OMEXDIA, REACTRAN)
    • Via spatial modelling (GIS) and/or through
    • Larger scale shelf sea modelling (ERSEM)

There is potential for students to collect suitable experimental samples at sea, through cruises on the Cefas Endeavour.


University of Southampton

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre, Southampton.

Specific training (provided through UoS and Cefas) will include the use of laboratory flumes, sampling techniques and modelling using COMSOL and/or R and ERSEM. Links with Cefas will allow the student to participate in the Cefas studentship programme/days and access to additional informal training opportunities on statistical modelling/coding, policy content and priorities under climate change and blue carbon programmes.



Eligibility & Funding Details: 

Please see https://inspire-dtp.ac.uk/how-apply for details.

Background Reading: 

Luisetti et al., 2019. Quantifying and valuing carbon flows and stores in coastal and shelf ecosystems in the UK. Ecosystem Services, 35: 67-76

Diesling et al, 2017. Predicting the standing stock of organic carbon in surface sediments of the North-West European continental shelf. Biogeochemistry, 135: 182-200.

Huettel, M. Berg, P. and Kosta, J.E. 2014. Benthic Exchange and biogeochemical cycling in permeable sediments. Annual Reviews of Marine Science, 6:23-51