Shelf-seas support up to one fifth of global primary productivity and thus help sustain fisheries and regulate global climate by taking up carbon dioxide (CO2). This CO2 uptake function is dubbed the 'shelf-sea carbon pump', which is at the heart of NERC's £6 million-Shelf Sea Biogeochemistry (SSB) research programme. This PhD project will be embedded within the SSB programme and make direct contributions to key research questions, such as the magnitude of the current annual exchange of carbon between UK/European shelf seas, the atmosphere, and the open ocean as well as physical and biogeochemical controls on shelf primary production, from the local to the shelf sea scale.
In particular, you will measure net production (N) based on underway measurements of oxygen/argon concentration ratios to constrain the biological component of the shelf-sea pump. This technique together with gross production (G) measurements based on triple oxygen isotope ratios of dissolved oxygen have emerged as alternative biogeochemical approaches to traditional bottle incubations. These biogeochemical methods provide rates at unprecedented temporal and spatial resolution, are less laborious and the derived rates are free from errors caused by increased mortality or exclusion of grazers due to enclosure of the sample.

This project will involve shipboard membrane inlet mass spectrometry and triple oxygen isotope ratio analyses in discrete samples, combined with estimates of air-sea exchange using satellite remote sensing. The triple oxygen isotope-based gross production estimates, G(17O), will be compared with G estimated from fast repetition rate fluorescence, G(FRRF). The project will also explore whether differences found in previous G(FRRF) and G(17O) comparisons can be reduced by using recent advances in protocols for the interpretation of FRRF data (Oxborough et al., 2012).
Led by UEA, the studentship will be co-supervised by Dr Suzanne Painting (Cefas), Dr David Suggett (University of Essex), Dr Jamie Shutler (Plymouth Marine Laboratory). The SSB programme will provide data to help quantify and understand variations in production rates, e.g. physical transport rates including vertical diffusion, phytoplankton community composition, grazing pressure, etc. Information on the community composition will help to improve gross production estimates if the isotopic composition of the photosynthetic end-members proves to be species-dependent as recently suggested (Kaiser, 2011).

Requirements, training and opportunities: We seek a student with good laboratory, practical and technical skills and at least a BSc Honours 2:1 or MSc degree in either chemistry, environmental sciences, oceanography, physics, biology or another relevant science. You are expected be fit and able to join two research cruises of at least 4 weeks' duration each. Experience in the use of modern mass spectrometry, marine optical techniques and remote sensing is desirable, but not essential. Visits to partner labs Cefas (Lowestoft), University of Essex and Plymouth Marine Laboratory will be integrated into the project. You will participate in regular SSB meeting and attend national and international conferences to present your results. You will be enrolled in the UEA Science Graduate School and acquire transferable skills in IT, management and communications, while participating in research of global significance.

(i) Luz & Barkan (2000) Assessment of oceanic productivity with the triple-isotope composition of dissolved oxygen, Science 288: 2028, 10.1126/science.288.5473.2028
(ii) Kaiser et al. (2005) Marine productivity estimates from continuous oxygen/argon ratio measurements by shipboard membrane inlet mass spectrometry, Geophys. Res. Lett. 32: L19605, 10.1029/2005GL023459
(iii) Suggett et al. (2009) Comparing electron transport with gas exchange: parameterising exchange rates between alternative photosynthetic currencies for eukaryotic phytoplankton, Aquat. Microb. Ecol. 56: 147, 10.3354/ame01303
(iv) Kaiser (2011) Technical note: Consistent calculation of aquatic gross production from oxygen triple isotope measurements, Biogeosciences 8: 1793, 10.5194/bg-8-1793-2011
(v) Oxborough et al. (2012) Direct estimation of functional PSII reaction center concentration and PSII electron flux on a volume basis: a new approach to the analysis of Fast Repetition Rate fluorometry (FRRf) data, Limnol. Oceanogr. Meth. 10: 142, 10.4319/lom.2012.10.142