Sulphur is an essential element for living organisms and emissions of the sulphur trace gas dimethyl sulphide [(CH3)2S; DMS] from the sea to the air is a vital pathway in the global sulphur cycle. Additionally DMS oxidises rapidly in air to produce particles that may then contribute to cooling the climate through cloud formation. The major DMS precursor is dimethylsulfoniopropionate [(CH3)2S+CH2CH2COO-; DMSP], a cellular component of marine algae that has properties in common with well-known compatible solutes. 

Studies on the intracellular DMSP concentration for a range of marine phytoplankton cultures published in the late 1980's by Keller and co-workers introduced the concept that the prymnesiophytes and dinoflagellates are the major DMSP-producing phytoplankton groups and that diatoms generally have low DMSP:carbon ratios (see Stefels et al 2007). These studies and the field data available at that time influenced the research field by paving the way to research on species with high intracellular DMSP concentrations especially Emiliania huxleyi and various Phaeocystis species.

Fast forwarding to today, we can find various examples of high-DMSP level diatom strains from estuarine, benthic and ice algal communities (e.g. Tison et al 2010). Additional cellular roles have also been suggested for DMSP including that of lead compound in an anti-oxidant cascade that enables cells to detoxify the harmful reactive oxygen species produced under conditions including enhanced UV radiation, CO2 and Fe limitation, high copper levels and nutrient limitation. Various studies have shown that the intracellular DMSP concentration of diatoms can increase substantially under nutrient limitation or stress conditions (e.g. Franklin et al 2012; Spielmeyer and Pohnert 2012). Given that diatoms are a major component of many marine communities perhaps accounting for up to 40% of marine primary production (Sarthou et al 2005) the current evidence suggests that it would be worthwhile to do further physiological, field and modelling research to examine the role of diatoms in the DMS cycle today and how this could change in the future. This would be the focus of the PhD project.

The student will join the Marine Trace Gas Biology Laboratory. Experimentation on phytoplankton cultures will be central to the project and some field-based research should be possible. The student will have access to a wide range of equipment e.g. cell counting and characterisation equipment, controlled light and temperature incubators, fluorescence microscopy, gas chromatography and liquid chromatography instrumentation. The project would suit a self-motivated and resourceful student, with a good experimental skills and practical ingenuity. The ideal candidate would have relevant analytical skills and experience of working with phytoplankton cultures.  Applicants will need a 1st class or 2i BSc degree in the Biological, Chemical or Environmental Sciences, Marine Biology, Oceanography, Plant Sciences and/or an MSc in this subject range.

Stefels, J., Steinke, M. Turner, S., Malin, G. & Belviso. S. 2007. Environmental constraints on the production of the climatically active gas dimethylsulphide (DMS) and implications for ecosystem modelling. Biogeochemistry 83(1-3): 245-275.

Tison, J.L., Brabant, F., Dumont, I. and Stefels, J. 2010 High-resolution dimethyl sulfide and dimethylsulfoniopropionate time series profiles in decaying summer first-year sea ice at Ice Station Polarstern, western Weddell Sea, Antarctica. Journal of Geophysical Research – Geosciences 115: G04044, doi:10.1029/2010JG001427.

Franklin, D.J., Airs, R.L., Fernandes, M., Bell, T.G., Bongaerts, R.J., Berges, J.A. & Malin, G. 2012. Identification of senescence and death in Emiliania huxleyi andThalassiosira pseudonana: Cell staining, chlorophyll alterations, and dimethylsulfoniopropionate (DMSP) metabolism.  Limnology & Oceanography 57: 305-317. DOI: 10.4319/lo.2012.57.1.0305.

Spielmeyer, A. and Pohnert, G. 2012. Daytime, growth phase and nitrate availability dependent variations of dimethylsulfoniopropionate in batch cultures of the diatom Skeletonema marinoi. Journal of Experimental Marine Biology and Ecology 413: 121-130 doi:10.1016/j.jembe.2011.12.004.

Sarthou, G., Timmermans, K.R., Blain, S. & Treguer, P. (2005) Growth physiology and fate of diatoms in the ocean: a review. Journal of Sea Research 53: 25– 42.