How do foraminifera grow? Determining the role of cellular ion transport processes in biogenic marine calcite formation

Gavin Foster, Dr David Evans, Main Supervisor, University of Southampton,; Professor Sumeet Mahajan, University of Southampton,; Professor Jonathan Erez, Hebrew University of Jerusalem

The shells of calcifying planktonic marine organisms such as the foraminifera represent one of the largest long-term carbon sinks on Earth’s surface and are an important archive of geochemical systems that record past climate change. As such, and because the response of these organisms to anthropogenic climate change may be an important carbon cycle feedback, it is vitally important to understand how these organisms calcify. However, foraminifera biomineralisation is only poorly understood [1]. In particular, it is not known whether these organisms produce ‘low-magnesium’ calcite (<0.01 mol% MgCO3) by actively lowering the Mg concentration of seawater transported to the site of biomineralisation within the cell [2], or if other processes, such as nonclassical calcium carbonate precipitation (via amorphous calcium carbonate) alternatively enables the organism to control shell chemistry.

Solving this issue would enable us to understand the sensitivity of calcification to past, present, and future environmental change.

To do so, this project will apply a suite of techniques to the study live foraminifera, including confocal and Raman microscopy, and isotope labelling experiments. Ultimately, this information will be built into a biomineralisation model to help mechanistically underpin our understanding of the extent to which marine organisms will be impacted by future climate change and ocean acidification, within the framework of two recently-funded projects tackling this issue and a wider team of researchers.


As the most abundant CaCO3 producers in the modern ocean, the project will focus on understanding the biomineralisation processes of the ‘low-magnesium’ foraminifera, live-collected from the Red Sea as part of this project. Previous work has suggested that active Mg transport may be a key process involved in the calcification process of these organisms [2], such that a key goal will be to understand whether the production of low-Mg calcite is possible as a result of active regulation of the calcification site Mg/Ca ratio. To do so, the project will:

1] Observe ion transport during the calcification process of live planktonic foraminifera in vivo by using confocal microscopy coupled with fluorescent indicators, with a focus on determining whether active magnesium transport is a key component of the biomineralisation process.

2] Couple the observational data with laboratory culture experiments of foraminifera grown in the presence of isotope labels to determine the transport dynamics of these key ions.

3] Constrain the importance of non-classical CaCO3 formation pathways [3] in this group of organisms by determining the presence or absence of amorphous calcium carbonate at the calcification site and/or within cellular compartments using Raman microscopy and multimodal CARS microscopy.

The information generated here will ultimately be synthesised together to produce a new, quantitative biomineralisation model for the foraminifera.

University of Southampton/National Oceanography Centre

The Graduate School of the School of Earth Sciences at the University of Southampton 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 School of Ocean and Earth Science.

The project will provide interdisciplinary training and transferable skills that will add value for a career in academia or industry. Specifically, the candidate will be trained in:

  • Extensive experience in working with live marine organisms (foraminifera), including the collection of these organisms via plankton towing and maintenance under controlled laboratory conditions. This part of the project will involve prolonged research visits with collaborative partners at the Hebrew University of Jerusalem and the Interuniversity Institute for Marine Sciences in Eilat, Israel.
  • Training and extensive experience in the use of confocal microscopy to observe intracellular processes in vivo, including the use of fluorescent tracers.
  • Analytical geochemistry, including working in ultra-clean laboratories, the operation of (multi collector) inductively coupled plasma mass spectrometers, and data processing.
  • The use of Raman spectroscopy to noninvasively observe nonclassical calcification processes.
  • The use of computer-controlled titration equipment and the production of amorphous and crystalline materials under tightly controlled conditions.
  • The development and application of numerical models to geochemical datasets and (bio)mineralisation.
  • Proficiency in programming languages (Matlab/python) including for the purposes of building geochemical models.
  • Quantitative and qualitative analytical skills.
  • Scientific communication through multiple media and at various local, national and international conferences/meetings.


Eligibility & Funding Details:

Funding: This project is fully funded to cover UK/Home tuition fees and stipend



Background Reading: 

[1] Erez, J. (2003). The source of ions for biomineralization in foraminifera and their implications for paleoceanographic proxies. Reviews in mineralogy and geochemistry, 54(1), 115-149.

[2] Zeebe, R. E., & Sanyal, A. (2002). Comparison of two potential strategies of planktonic foraminifera for house building: Mg2+ or H+ removal? Geochimica et Cosmochimica Acta, 66(7), 1159-1169.

[3] Evans, D., Webb, P. B., Penkman, K., Kroger, R., & Allison, N. (2019). The characteristics and biological relevance of inorganic amorphous calcium carbonate (ACC) precipitated from seawater. Crystal Growth & Design, 19(8), 4300-4313.