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  Iron availability to marine phytoplankton in a changing ocean

   Department of Earth, Ocean and Ecological Sciences

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  Dr Fengjie Liu, Dr P Salaun, Dr Martha Gledhill  No more applications being accepted  Funded PhD Project (UK Students Only)

About the Project

Anthropogenic greenhouse gas emissions such as carbon dioxide (CO2) are causing climate change, global warming, and ocean acidification ( Phytoplankton sequester 50% of global CO2 and supply >50% of new nitrogen used for primary production, which sustains the entire food chains in the oceans (Falkowski 2012). Other than light and major nutrients, phytoplankton growth is strongly influenced by the availability of the metal iron (Fe) (Boyd et al. 2007; Browning et al. 2017; Moore et al. 2013), because the metal is essential for photosynthesis and nitrogen fixation, but is also very scarce in the open ocean due to its unique chemistry. The bioavailability of Fe is therefore tightly linked to atmospheric CO2 change as well as ocean carbon and nitrogen cycles.

The Intergovernmental Panel on Climate Change (IPCC) 2018 report concluded that the large error in predicting marine CO2 cycling and primary productivity was partly a result of poor knowledge on the bioavailability of Fe (IPCC 2018). In order to understand how Fe controls atmospheric CO2 levels and oceanic productivity, it is therefore important to first understand the controls on the availability of the metal to marine phytoplankton. The prevailing view is that more than 99% of Fe in seawater is complexed by naturally occurring organic ligands (Gledhill and Buck 2012) and such organic complexation is believed to reduce Fe availability to marine phytoplankton (Morel et al. 2008). However, data from recent studies are inconsistent with this long-standing paradigm as it is observed that natural seawater Fe was highly available to phytoplankton (Shaked et al. 2021).

The project will seek to resolve this paradox. Specifically, we want to know 1) Is organically complexed Fe a major contributor in phytoplankton nutrition? And/or 2) How the ongoing ocean changes (e.g., acidification) alter Fe bioavailability? We will use model ligands and phytoplankton species to unravel the underlying mechanisms, and use naturally occurring ligands and phytoplankton assembles collected during oceanographic cruises to further examine the ideas. The project will involve biological (e.g. algae incubation experiments), chemical (e.g. extraction and characterisation of organic ligands) and modelling tools (e.g., Fe speciation) to improve our knowledge of Fe bioavailability. This is a timely interdisciplinary project that will ultimately improve our capacity to model and predict the role of Fe nutrition in the changing ocean.

This exciting PhD project comes with a range of research and training opportunities. The student will work on a highly topical issue with an international team, in a multi-disciplinary environment, will be able to participate in GEOTRACES oceanographic cruises (in the Equatorial Pacific and/or the Indian Ocean) and will have the opportunity to carry out some of the research at the GEOMAR Helmholtz Centre for Ocean Research in Germany, one of the world’s leading marine science institutions. The student will be trained in analytical techniques for seawater chemistry, state-of-the-art culturing methods for marine phytoplankton, in the use of chemical/modelling tools for metal speciation. They will be strongly encouraged to attend national/international conferences and publish their research. A career development PhD training program provided by the University of Liverpool will also be provided.

We are looking for a 1st class student with an oceanographic, biological and/or chemical background. If you are interested, please contact Dr Fengjie LIU ([Email Address Removed]), for more information.

To apply for this opportunity, please visit: and click the 'Ready to apply? Apply online.'

Biological Sciences (4) Chemistry (6) Environmental Sciences (13) Geology (18)

Funding Notes

This competitive funded studentship supports 3.5 years of full-time studies, covering UK fees (, annual stipend of £15,843 and a research training support grant of £5000 for the duration of the studies.
Shortlisted candidates will have an interview on the 9th of March 2022 (date tbc).
This opportunity is open to UK and international applicants. If you are an international student, you will need to cover the differences in fees.


Boyd, P. W. and others 2007. Mesoscale iron enrichment experiments 1993-2005: synthesis and future directions. Science 315: 612-617.
Browning, T. J. and others 2017. Nutrient co-limitation at the boundary of an oceanic gyre. Nature 551: 242-246.
Falkowski, P. 2012. Ocean Science: The power of plankton. Nature 483: S17.
Gledhill, M., and K. Buck. 2012. The organic complexation of iron in the marine environment: a review. Frontiers in Microbiology 3.
IPCC. 2018. Summary for Policymakers, p. 32. In P. Z. V. Masson-Delmotte, H. O. Pörtner, D. Roberts, J. Skea, P. R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Chen, X. Zhou, M. I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, T. Waterfield [ed.], Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. World Meteorological Organization.
Moore, C. M. and others 2013. Processes and patterns of oceanic nutrient limitation. Nature Geoscience 6: 701-710.
Morel, F. M. M., A. B. Kustka, and Y. Shaked. 2008. The role of unchelated Fe in the iron nutrition of phytoplankton. Limnology and Oceanography 53: 400-404.
Shaked, Y., B. S. Twining, A. Tagliabue, and M. T. Maldonado. 2021. Probing the bioavailability of dissolved iron to marine eukaryotic phytoplankton using in situ single cell iron quotas. Global Biogeochemical Cycles 35: e2021GB006979.
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