The role of iron in nitrogen fixation and photosynthesis in changing polar oceans

Dr Maeve Lohan, Dr Amber Annett, Tom Bibby, SOES

Iron is essential for marine primary production due to its enzymatic requirement in key metabolic functions such as photosynthesis, respiration and the acquisition of macronutrients such as nitrogen fixation [1].  Oceanic photosynthesis powers life in the oceans and is fundamental to the carbon-cycle and hence the climate [2]. In many parts of the ocean, particularly the Southern Ocean, iron availably limits the growth of phytoplankton.

As the Arctic Ocean warms and becomes ice free, primary productivity, which underpins the entire Arctic ecosystem, has already increased, but the future trend is unclear due to the ongoing debate on Arctic micro-nutrient limitation and the imbalance in the Arctic nitrogen budget [3]. Nitrogen fixation, which has a large iron requirement may therefore be a critical source of nitrogen to sustain contemporary and future ocean productivity.

We aim to carryout shipboard bioassays to investigate the role of iron for nitrogen fixation in the Arctic and to understand how iron, nutrients and light the iron-limited Southern Ocean. This project will provide important new insights into the role of iron in both nitrogen fixation and photosynthesis in a time when the climate is changing rapidly.


  1. You will participate in 2 NERC funded research cruises, one to the Arctic (Barents Sea & Fram Strait) and the second to South Atlantic into the iron limited Southern Ocean. On both of these research cruises we will conduct shipboard bioassays to investigate the role of iron in nitrogen fixation and photosynthesis. This will provide a broader context to the laboratory work.
  2. Trace metal concentrations will be determined in both the dissolved and particulate form using High Resolution Inductively Coupled Mass Spectrometry (HR-ICP-MS)
  3. Using iron isotopes we will fingerprint the sources of iron to these different regions
  4. The student will work with other members of the N-ARC and NPOP project to provide a large scale ocean view on the role of iron in nitrogen fixation and photosynthesis in regions undergoing rapid climate change.



All doctoral candidates will enroll in the Graduate School of NOCS (GSNOCS), where they will receive specialist training in oral and written presentation skills, have the opportunity to participate in teaching activities, and have access to a full range of research and generic training opportunities. GSNOCS attracts students from all over the world and from all science and engineering backgrounds. There are currently around 200 full- and part-time PhD students enrolled (~60% UK and 40% EU & overseas).  Specific training will include:


  • Trace metal sample collection and analyses on board ship
  • Training in the sampling of natural phytoplankton communities and methods for experimental manipulation of natural communities on board ship
  • Training in state-of-the-art analytical techniques including inductively coupled plasma mass spectrometry (ICP-MS) for accurate and precise analysis of dissolved and particulate bioactive trace elements. Analytical work will be undertaken in our world-class trace metal clean facilities.
  • Analysis of complex multi-factor data as required to develop an understanding of multi-element cycling from cellular to ocean scales
  • Trace metal isotopes
  • Presenting research findings at international and nation conferences


Eligibility & Funding Details: 

Please see for details.


Background Reading: 

[1] Lohan, M.C. & Tagliabue, A. (20XX). Ocean Micronutrients: Trace metals that are essential for marine life. Elements: doiL10.2138/gselements.14.6

[2] Karl DM. Solar energy capture and transformation in the sea. Elem Sci Anth. 2014;2:21. DOI:

[3] Arrigo & van Dijken (2015). Continued increases in Arctic Ocean primary production. Prog. Oceangr. 135: 60.