Investigating the stoichiometry and binding of trace elements to marine particulate matter


To apply please use the online application form. Simply search for PhD Environmental Sciences (and select the entry point of October 2023), then clearly state that you are applying for a PhD studentship and name the project at the top of your personal statement.

Online application

Before applying, please ensure you have read the Doctoral College’s general information on applying for a research degree.

For more information on the admissions process please contact

Director of Studies: Dr Angela Milne
2nd Supervisor: Dr Simon Ussher
3rd Supervisor: Dr Martha Gledhill (, GEOMAR Helmholtz Centre for Ocean Research Kiel 
Applications are invited for a 3.5 years PhD studentship. The studentship will start on 01 October 2023.
Project description

Scientific background
Particulate matter (PM) is a key constituent involved in the cycling of elements that support marine life and control ocean productivity as part of the ocean’s ‘biological pump’.  This cycling can impact the distribution and availability of essential trace nutrients to marine organisms, including iron. The availability of iron limits primary production in a third of the world’s oceans, impacting the efficiency of the biological pump so influencing earth’s climate.
Ocean PM consists of organic (humics, exopolymeric-substances) and inorganic material (clays, silicates, hydroxides).  Important information about elemental cycling associated with PM can be garnered from elemental stoichiometry (their ratios) and factors that influence that stoichiometry. However, while there have been investigations relating to the stoichiometries of nitrogen and phosphorus associated with dissolved and particulate matter, the stoichiometries of trace elements are less studied.
The overall aim of this project is to assess trace elemental stoichiometry of PM from varied sources (e.g. open ocean, continental shelf) as well as the binding and/or release of those elements with any associated organic material. This project will provide in-depth understanding of element-particle dynamics for a deeper understanding of trace elemental cycling and spatial productivity.
Using clean-handling techniques, you will supplement existing PM samples by collecting PM from SW rivers and the Celtic Sea.  You will also have the opportunity to participate in a research cruise to the Southern Ocean.  You will subject collected PM to leach and digestion procedures. You will perform controlled incubations (e.g. changes in pH, ionic strength, element additions) to assess the binding and release of elements, and any subsequent element-complexation with organic matter.  Samples to assess impacts on microbial communities will also be gathered to aid interpretation for incubations.
You will receive comprehensive training in clean-handling, both in land-based laboratories and at sea, and advanced analytical techniques which will be required to undertake the experiments and respective analyses.  You will spend time in Germany developing skills to extract, analyse and interpret trace elements bound to organic matter.
Person specification
We are looking for an individual with a degree in Chemistry or Earth, Ocean, or Environmental Science.
Funding notes
This project has been shortlisted for funding by the ARIES NERC DTP and will start on 1 October 2023.
Successful candidates who meet UKRI’s eligibility criteria will be awarded a NERC studentship for 3.5 years, covering fees, stipend (£17,668 p.a. for 2022-23 rate) and research funding. International applicants (EU and non-EU) are eligible for fully-funded UKRI studentships.
ARIES students benefit from bespoke graduate training and £2,500 for external training, travel and conferences.
ARIES is committed to equality, diversity, widening participation and inclusion. Academic qualifications are considered alongside non-academic experience. Our recruitment process considers potential with the same weighting as past experience.
For information and full eligibility visit
Please clearly state the name of the studentship project code MILNE_P23ARIES that you are applying for on your personal statement.
If you wish to discuss this project further informally, please contact Dr Angela Milne.
Please see our 'how to apply for a research degree' page for a list of supporting documents to upload with your application.
For more information on the admissions process generally, please contact
The closing date for applications is 23:59 (UK Time) 11 January 2023. 


1 Wyatt, N. J., Milne, A., Achterberg, E. P., Browning,T. J., Bouman, H. A., Woodward, E. M. S., & M. C. Lohan (2021). Seasonalcycling of zinc and cobalt in the south-eastern Atlantic along the GEOTRACESGA10 section. Biogeosciences 18(14):4265-4280. .

2 White, C., Ussher, S. J., Fitzsimons, M. F., Atkinson,S., Woodward, E. M. S., Yang, M. & T. G. Bell (2021). Inorganic nitrogenand phosphorus in Western European aerosol and the significance of drydeposition flux into stratified shelf waters. Atmospheric Environment 261:118391. .

3 Schmidt, K., Birchill, A. J., Atkinson, A., Brewin, R.J. W., Clark, J. R., Hickman, A. E., Johns, D. G., Lohan, M. C., Milne, A.,Pardo, S., Smyth, T. J., Tarran, G. A., Widdicombe, C. E., Woodward, E. M. S.,& S. J. Ussher (2020). Increasing picocyanobacteria success in shelf waterscontributes to long-term food web degradation. Global Change Biology 26 (10):5574-5587. .

4 Gledhill, M., Hollister, A., Seidel, M., Zhu, K.,Achterberg, E.P., Dittmar, T., Koschinshy, A. (2022) Trace metal stoichiometryof dissolved organic matter in the Amazon plume. Sci. Adv. 8, eabm2249.

5 E. J. Zakem, N. M. Levine (2019)Systematic variation in marine dissolved organic matter stoichiometry andremineralization ratios as a function of lability. Global Biogeochem. Cycles33, 1389–1407.