Unravelling oceanic multi-element cycles using single cell ionomics

Prof Christopher Moore, Gavin Foster, Dr Maeve Lohan, Kate Hendry (BAS), Clara Manno (BAS)
Rationale: 

Oceanic elemental cycles are strongly influenced by marine microbes, including phytoplankton. Although it has long been recognised that the elemental composition of microbes is a key determinant of these cycles (1), analytical limitations mean current understanding is typically based on observations of limited numbers of elements averaged across mixed microbial communities. Appreciation of potentially important heterogeneities at individual and population levels and a more holistic understanding of multi-element cycling is thus lacking (1, 2). Consequently, single-cell analysis is a fast-growing field, but many techniques are hampered by low throughput. We aim to apply a new analytical tool (Time of Flight Inductively Coupled Plasma Mass Spectrometry, ToF-ICPMS) to facilitate rapid multi-element analysis of individual marine phytoplankton cells (3). This project will focus on the key question of how variability in (co-)limiting nutrient availability influences the multi-elemental cellular composition of non-limiting nutrients (2), which has significant consequences for understanding coupled nutrient cycling (1, 2). Although this problem has been addressed in specific cases on an element-by-element basis (1), we lack true multi-element (‘ionomic’) treatments (2), which also account for the heterogeneity of mixed natural communities. This project represents a key advance towards deeper understanding of multi-elemental ocean biogeochemical cycles.

Methodology: 

Although single-cell analysis has become increasing important for cellular biologists, its application in the marine sciences remains limited. Any methodology needs to be sensitive enough to detect the elements of interest in individual cells but rapid enough to generate statistically meaningful information at the level of the (sub-)populations within a community. ToF-ICPMS has recently emerged as the method of choice for single cell analysis, either through solution-mode (3) or via laser ablation. In this project different phytoplankton taxa will be grown both as monocultures and mixed cultures under controlled conditions of variable (co-limiting) nutrient (N, P, Fe, Mn, Zn) availability, to investigate how physiological limitation by one element influences the cellular composition of multiple other elements (those with mass numbers from P upwards) and how this varies between taxa and sub-populations (1, 2). This fundamental culture work will be complimented by measurements on samples of oceanic plankton collected from key locations (from local coastal waters to the Southern Ocean and hopefully all involving participation by the student) to explore elemental quotas and interactions in mixed natural communities. The project will thus generate novel data addressing key questions relating to the controls on coupled ocean nutrient cycling. 

Location: 
University of Southampton
Training: 

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 the School of Ocean and Earth Science. The student will also have the opportunity to interact with scientists at the British Antarctic Survey (BAS).

Specific training will include:

·         Training in solution-mode and laser ablation-mode ToF-ICPMS.

·         Training in phytoplankton culturing and (eco-)physiological characterization

·         Training in the sampling of natural phytoplankton communities and methods for experimental manipulation of natural communities

·         Analysis of complex multi-factor data as required to develop an understanding of multi-element cycling from cellular to ocean scales

There may be the opportunity to undertake fieldwork to sample natural communities at sea both locally to the UK but also further afield, including in the Southern Ocean.

Eligibility & Funding Details: 

Please see https://inspire-dtp.ac.uk/how-apply for details.

Background Reading: 
  1. Moore et al. (2013) Processes and patterns of upper ocean nutrient limitation. Nature Geoscience 6 701-710 DOI:10.1038/NGEO1765
  2. Jeyasingh et al. (2017) Ecological Stoichiometry beyond Redfield: An Ionomic Perspective on Elemental Homeostasis. Front. Microbiol. https://doi.org/10.3389/fmicb.2017.00722
  3. Von de Au, M, et al. (2020) Single cell-inductively coupled plasma-time of flight-mass spectrometry approach for ecotoxicological testing, Algal Research, 49, 101964 https://doi.org/10.1016/j.algal.2020.101964