How do Organic Nutrients Sustain Shelf Seas Productivity?

Second Supervisor (External Lead):  Dr Katherine Helliwell

Lead Supervisor (Director of Studies): Professor Mark Fitzsimons

Third Supervisor: Dr Andy Rees 

Applications are invited for a 3.5-year PhD studentship with Marine Research Plymouth – a collaborative partnership between the University of Plymouth, the Plymouth Marine Laboratory and the Marine Biological Association. The studentship is due to start on 1 October 2024.

This project is one of four topics available for the studentship. We anticipate supporting one position, which will be allocated to the best combination of candidate and project as they emerge from interviews across the pool of available topics. Browse all available topics.

Plymouth has been at the forefront of global marine research for more than a century, and today it is home to the largest concentration of marine researchers in the UK. Come and join our vibrant community of marine PhD students. 

Marine phytoplankton play vital roles in regulating the global climate, contributing almost half of net primary production. A major factor controlling phytoplankton assemblages is the availability of crucial nutrients including nitrogen (N) and phosphorus (P), the supply of which can vary dramatically in space and time. Most work examining the role of N and P in driving phytoplankton productivity has focussed on inorganic forms (e.g., nitrate and phosphate). By comparison, the roles of organic N and P forms (DON and DOP, respectively), which can make up to 50% of the dissolved N and P pools in seawater, are poorly understood. We recently demonstrated that marine phytoplankton are capable of assimilating organic N and P, even in the presence of high levels of inorganic nutrients. Additionally, we have found that the availability of organic N forms enhances organic P acquisition, suggesting that phytoplankton coordinate N and P signalling and uptake pathways in order to maximise acquisition of these essential nutrients. The aim of this project is to integrate field and laboratory methodologies to further examine organic N and P usage and coordination by phytoplankton in the Western English Channel.  

The project will aim to characterise the dissolved organic nutrient pools in relation to the seasonal succession of coastal phytoplankton communities. The student will characterise compositional changes within the DON and DOP pools in the Western English Channel over the course of the annual cycle, coupling field sampling (on the PML research vessel Quest) with analytical chemistry using HPLC.

Physiological experiments with a range of phytoplankton will also be conducted to examine the bioavailability of environmentally relevant DON and DOP forms. Additionally, the nature (timescale, specificity and extent) of coordination between DON availability and DOP acquisition will be examined.

The successful candidate will gain training in a wide range of field and laboratory skills, including analytical chemistry (chromatography), phytoplankton physiology and marine biogeochemistry, and will have access to professional development opportunities. 

Applicants should have a first or upper second class honours degree in an appropriate subject or a relevant masters qualification in physical or biological science with an analytical science component. The ideal candidate would be an enthusiastic, motivated individual interested in working at the intersect of field oceanography, analytical chemistry and microbiology.

Non-native English speakers must have an IELTS Academic score of 6.5 or above (with no less than 5.5 in any element) or equivalent.

The studentship is supported for 3.5 years and includes full home tuition fees plus a stipend at the 2024/25 rate (to be confirmed; compare the 2023/24 rate of £18,110 per annum). The last 6 months of the four-year registration period is a self-funded ‘writing-up’ period. The studentship will only fully fund those applicants who are eligible for home fees with relevant qualifications. Applicants normally required to cover international fees will have to cover the difference between the home and the international tuition fee rates (approximately £12,697 per annum at 2023/24 rate).

If you wish to discuss this project further informally, please contact Dr Katherine Helliwell.

Shortlisted candidates will be informed as soon as possible after the deadline, with interviews likely to take place in the second half of February. We regret that we may not be able to respond to all applications. Applicants who have not received a response within six weeks of the closing date should consider that their application has been unsuccessful on this occasion.