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Dr M Johnson
No more applications being accepted
Funded PhD Project (European/UK Students Only)
About the Project
This fully funded studentship is co-funded by Cefas (Centre for environment, fisheries and aquaculture science) and the faculty of science at UEA as part of their strategic alliance. It will be based around Cefas platforms (ships, autonomous moorings) but it is also anticipated that the project will be strongly linked to the £10M NERC research programme “Shelf Sea Biogeochemistry” (NERC-SSB; 2013-2017), in which most of the supervisory team and collaborators are involved. This means the successful applicant will be exposed to both policy-driven and academically driven research environments and networks outside of the immediate university environment.
The project will address key unknowns in the continental shelf carbon pump (CSCP), by
quantifying the role of dissolved organic matter (DOM) and transparent exopolymer particle (TEP) production in the 'over-consumption' of carbon i.e. the drawdown of DIC (dissolved inorganic carbon) in surface waters in excess of that predicted by Redfieldian C:N ratios. Ultimately this will lead to novel parameterisations for the representation of these processes in marine biogeochemical models such as ERSEM (the European Regional Seas Ecosystem Model; modelling focus for NERC-SSB).
The CSCP may be responsible for up to 25% of the CO2 exported from the atmosphere to the deep ocean globally; and be key for the rapid, long-term sequestration of anthropogenic CO2. Carbon pumping is enhanced by decoupling of the carbon to nutrient stoichiometry from that of the primary producers (the “Redfield ratio”; typically ~16:1 C:N). Such processes may act either via direct production of carbon-rich material by primary producers or by the preferential remineralisation of nutrient over carbon. Such processes are likely to be particularly important in the summer regime when Redfieldian recycled production should have no net effect on the DIC concentration (C and N cycling fully coupled), but accumulation and export of carbon rich organics allows additional CO2 uptake. Prowe et al. (2009) identify that the 'overflow production' of carbon-rich TEP under nutrient limitation may double DIC uptake per unit of nitrogen in surface waters of the North Sea compared to Redfieldian predictions.
The student will quantify inorganic and organic C and N pools and carbon overconsumption in the field; and derive parameterisations of TEP production and dissolved organic matter dynamics targetted to ERSEM. The student will participate in Cefas cruises in the North Sea on the RV Endeavour. TEP samples will be sent from SSB cruises in the Celtic Sea. Cefas Smartbuoy samples from the North Sea will be analysed for DOC and DON, extending an existing data set, giving insight into high-frequency dynamics of DOM and its stoichiometry by validation of process measurements and ERSEM output. Subsequent work may involve laboratory study of phytoplanton or mixed community cultures, further field or modelling work depending on the student's interests. The supervisory team consists of Martin Johnson, Gill Malin and Dorothee Bakker (UEA), Naomi Greenwood (Cefas) and collaborators Claire Mahaffey (Liverpool) and Luca Polimene (Plymouth Marine Laboratory).
The project will address key unknowns in the continental shelf carbon pump (CSCP), by
quantifying the role of dissolved organic matter (DOM) and transparent exopolymer particle (TEP) production in the 'over-consumption' of carbon i.e. the drawdown of DIC (dissolved inorganic carbon) in surface waters in excess of that predicted by Redfieldian C:N ratios. Ultimately this will lead to novel parameterisations for the representation of these processes in marine biogeochemical models such as ERSEM (the European Regional Seas Ecosystem Model; modelling focus for NERC-SSB).
The CSCP may be responsible for up to 25% of the CO2 exported from the atmosphere to the deep ocean globally; and be key for the rapid, long-term sequestration of anthropogenic CO2. Carbon pumping is enhanced by decoupling of the carbon to nutrient stoichiometry from that of the primary producers (the “Redfield ratio”; typically ~16:1 C:N). Such processes may act either via direct production of carbon-rich material by primary producers or by the preferential remineralisation of nutrient over carbon. Such processes are likely to be particularly important in the summer regime when Redfieldian recycled production should have no net effect on the DIC concentration (C and N cycling fully coupled), but accumulation and export of carbon rich organics allows additional CO2 uptake. Prowe et al. (2009) identify that the 'overflow production' of carbon-rich TEP under nutrient limitation may double DIC uptake per unit of nitrogen in surface waters of the North Sea compared to Redfieldian predictions.
The student will quantify inorganic and organic C and N pools and carbon overconsumption in the field; and derive parameterisations of TEP production and dissolved organic matter dynamics targetted to ERSEM. The student will participate in Cefas cruises in the North Sea on the RV Endeavour. TEP samples will be sent from SSB cruises in the Celtic Sea. Cefas Smartbuoy samples from the North Sea will be analysed for DOC and DON, extending an existing data set, giving insight into high-frequency dynamics of DOM and its stoichiometry by validation of process measurements and ERSEM output. Subsequent work may involve laboratory study of phytoplanton or mixed community cultures, further field or modelling work depending on the student's interests. The supervisory team consists of Martin Johnson, Gill Malin and Dorothee Bakker (UEA), Naomi Greenwood (Cefas) and collaborators Claire Mahaffey (Liverpool) and Luca Polimene (Plymouth Marine Laboratory).
Funding Notes
This studentship will cover the full cost of tuition fees and provide a Research and Training Support Grant of £10,794.
References
Toggweiler, J. (1993). Carbon overconsumption. Nature, 363, 210–211.
(ii) Prowe, A. E. F., Thomas, H., Pätsch, J., Kühn, W., Bozec, Y., Schiettecatte, L.-S., Borges, A. V., et al. (2009). Mechanisms controlling the air–sea flux of CO2 in the North Sea. Continental Shelf Research, 29(15), 1801–1808. doi:10.1016/j.csr.2009.06.003
(iii) Kahler, P., & Koeve, W. (2001). Marine dissolved organic matter: can its C: N ratio explain carbon overconsumption? Deep Sea Research Part I: Oceanographic Research, 48, 49–62.
(iv) Johnson, M. T., Greenwood, N., Sivyer, D. B., Thomson, M., Reeve, A., Weston, K., & Jickells, T. D. (2012). Characterising the seasonal cycle of dissolved organic nitrogen using Cefas SmartBuoy high-resolution time-series samples from the southern North Sea. Biogeochemistry, online first. doi:10.1007/s10533-012-9738-8
(ii) Prowe, A. E. F., Thomas, H., Pätsch, J., Kühn, W., Bozec, Y., Schiettecatte, L.-S., Borges, A. V., et al. (2009). Mechanisms controlling the air–sea flux of CO2 in the North Sea. Continental Shelf Research, 29(15), 1801–1808. doi:10.1016/j.csr.2009.06.003
(iii) Kahler, P., & Koeve, W. (2001). Marine dissolved organic matter: can its C: N ratio explain carbon overconsumption? Deep Sea Research Part I: Oceanographic Research, 48, 49–62.
(iv) Johnson, M. T., Greenwood, N., Sivyer, D. B., Thomson, M., Reeve, A., Weston, K., & Jickells, T. D. (2012). Characterising the seasonal cycle of dissolved organic nitrogen using Cefas SmartBuoy high-resolution time-series samples from the southern North Sea. Biogeochemistry, online first. doi:10.1007/s10533-012-9738-8
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