PhD Studentship: Environmental Controls on Productivity in Viruses of Marine Phytoplankton: Linking Modelling With Experimental Ecology

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.


Dr Hywel Williams,
College of Life and Environmental Sciences, University of Exeter – Main supervisor
Dr Mike Allen, Plymouth Marine Laboratory
Dr Darren Clark, Plymouth Marine Laboratory
Dr Susan Kimmance, Plymouth Marine Laboratory

Project description:  Marine viruses are the most abundant biological entities on the planet and play a fundamental role in the marine carbon cycle. Yet they are routinely omitted from marine ecosystem models used to predict global carbon fluxes, primarily because increasingly available empirical data has not yet been translated into a coherent theoretical framework for viral impacts on carbon and nutrient cycling. This interdisciplinary project will tackle this problem, combining state-of-the-art microbial ecosystem modelling (conducted at University of Exeter) with controlled laboratory culture experiments (conducted at Plymouth Marine Laboratory), to address the key relationship between viral productivity and environmental conditions.

Viral productivity (rate of production of new virus particles) has a first-order effect on plankton mortality (hence turnover, nutrient cycles, and ecosystem productivity). We will apply a novel adaptive modelling methodology to test the core hypothesis that environmental conditions affect viral productivity via intermediate effects on resource allocation within the infected cell. We will focus on viruses infecting two important classes of phytoplankton – cyanobacteria and coccolithophores – and how their productivity is affected by environmental gradients of light, temperature, and nutrient availability.

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We have pioneered an adaptive modelling framework (Clark et al, 2013) which predicts traits of marine phytoplankton as the outcome of environmental conditions and simulated natural selection acting on a diverse set of plankton types. This approach has successfully been used to predict phytoplankton cell size and chlorophyll content along seasonal, latitudinal and vertical gradients of light and nutrient availability. Elsewhere we have used simple models of host-virus evolutionary ecology to explain observed patterns of interaction in plankton communities. Here we will apply this expertise to build a new mechanistic model, based on stoichiometric constraints and resource allocation within the infected cell (e.g. investment in quantity vs quality of virus particles), to determine virus productivity under varying environmental conditions. We will then validate the model against literature datasets for cyanobacteria-cyanophage and with a new set of culture experiments using established coccolithophore and coccolithovirus strains (Allen et al. 2007). These experiments will assess the impact of light, temperature and nutrients on viral burst size, infection rates, and total production, under controlled laboratory conditions.

The final strand of the project will be to embed our new plankton-virus model into regional/global biogeochemical models, to make predictions of viral impacts on marine ecosystem processes. Validation data for this part of the project will come in part from the Western Channel Observatory, routinely monitored by supervisors MA and SK and colleagues at PML.

The closing date for applications is midnight Friday 10 January 2014.

For further information, please visit the Apply button below.

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