PhD Studentship: Predicting the Effects of Global Warming on Marine Phytoplankton and Oceanic Biogeochemical Cycles



This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP).

Studentships will be awarded on the basis of merit and will commence in September 2014. For eligible students the award will cover UK/EU tuition fees and an annual stipend (in 2013/14 this was £13,726 for full-time students, pro rata for part-time students) for three and a half years.

Supervisors:

Dr Gabriel Yvon-Durocher, College of Life and Environmental Sciences, University of Exeter
Prof Timothy Lenton, College of Life and Environmental Sciences, University of Exeter
Prof Nicholas Smirnoff, College of Life and Environmental Sciences, University of Exeter
Dr Glen Wheeler (Plymouth Marine Laboratory/Marine Biological Association of the United Kingdom)

Project description:  This project will use a series of experiments on marine phytoplankton to further develop our sub-cellular model of phytoplankton physiology – the ‘EVE’ model – by characterising the mechanistic basis for the thermal acclimation of metabolic rate and elemental composition. Because the EVE model is embedded within an ocean general circulation model (GCM) these refinements will help to reduce uncertainty in predictions of the effects of ocean warming on marine phytoplankton and the biogeochemical cycles they mediate. The project will test the hypothesis that, across the major phyla of marine phytoplankton, there are analogous sub-cellular resource-allocation trade-offs, which underpin the thermal acclimation of metabolism and elemental composition.

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The EVE model assumes acclimation involves changes in sub-cellular resource allocation to P-rich biosynthesis machinery (especially ribosomes), to N-rich photosynthetic machinery, and to cellular structure. The increased efficiency of ribosomes at higher temperatures leads to the prediction that warming will increase cellular N:P ratios, with consequent implications for biogeochemical cycles. This prediction is supported by evidence from a meta-analysis of experiments on the response of the N:P ratio of phytoplankton biomass to variation in temperature.

However, we currently lack the data to explore the mechanisms that link temperature and elemental composition to the specific biochemical and physiological processes, which are needed to adequately parameterise the temperature dependence of the key components of the model, resulting in large uncertainties in the model’s predictions.

The student will therefore measure the thermal acclimation of selected marine phytoplankton isolates, encompassing broad phylogenetic diversity (diatoms, haptophytes, prasinophytes, dinoflagellates and cyanobacteria). In each species, the ability of growth, respiration and photosynthesis to acclimate to temperature will be assessed along with changes in elemental composition (C:N:P stoichiometry). These measurements will be followed up by detailed biochemical and cell biological approaches to identify the underlying mechanistic basis of thermal acclimation. This will include the following: relative per cell concentrations of the key respiratory and photosynthetic proteins (using multiple reaction monitoring with a triple quadrupole mass spectrometer for species with a sequenced genome- at least 3 of those selected); rRNA concentrations (Agilent Bioanalyser); mitochondrial and chloroplast cross- sectional areas (light and confocal microscopy).

The student will use this experimental evidence to make structural and parameter refinements to the EVE model to explore their consequences for marine biogeochemical cycles in the context of the ocean GCM.

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The closing date for applications is midnight Friday 10 January 2014. Interviews are expected to take place in February.

For further information, please visit the Apply button below. 

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