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Postgraduate research project

Size does matter: linking particle size to ocean carbon storage

Competition funded View fees and funding
Type of degree
Doctor of Philosophy
Entry requirements
2:1 honours degree View full entry requirements
Faculty graduate school
Faculty of Environmental and Life Sciences
Closing date

About the project

The depth in the ocean at which sinking organic carbon is remineralised back into CO2 is crucial to setting atmospheric CO2 concentration. In this project, you will explore the links between remineralisation depth, particle size and plankton size by building a simple mechanistic model on the basis of global datasets.

The size and shape of sinking particles is likely key to determining their remineralisation depth, as slower sinking particles are likely to be remineralised at a shallower depth.  This leads to a “particle size-remineralisation feedback” hypothesis, such that under climate change-driven warming conditions plankton size structure shifts to smaller organisms due to increasing stratification, which leads to a shift to smaller sinking particles and so shallower remineralisation of organic carbon and nutrients. This latter would then increase nutrient availability in the upper ocean, which could drive increased primary production and carbon flux. The overall effect would be a dampening of the expected decline in primary production and carbon flux as a result of climate change.  If correct, then current IPCC projections, which omit this potential negative feedback, are overestimating reductions in future ocean carbon storage.  

We will test this hypothesis by using existing public databases to explore the relationship between the size of phytoplankton and the size, type and shape of sinking particles, and the links to remineralisation depth. We will build a simple mechanistic model incorporating (dis)aggregation, remineralisation and sinking to gain understanding of how different processes change the particle size spectrum. We will incorporate the effects of environmental factors such as temperature and oxygen concentration, so that we can make predictions about the impacts of climate change. 

The student will be embedded in a large international consortium project of carbon cycle scientists

Supervisory team

The supervisory team includes supervisors from several organisations, including our INSPIRE Partners. Please contact the Lead Supervisor for more information about the team.


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 National Oceanography Centre, Southampton. Specific training will include use of autonomous platforms, satellite data, model output analysis, ocean biogeochemistry and interaction with climate. 

The student will develop skills in the in-demand areas of quantitative analysis of climate- and environment-relevant data.  The student will be part of the Ocean BioGeosciences group at NOC, which is renowned globally as a centre of excellence in biological carbon pump research. The student may attend university Masters level lectures to gain relevant background knowledge. There will also be the opportunity to participate in a research cruise, likely in the North Atlantic.