MRI: Acquisition of a field-deployable mass spectrometer for biogeochemical research and education.

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This award will facilitate the purchase of a Proton Transfer Reaction Mass Spectrometer (PTR-MS) to study a variety of questions relating to the biogeochemical cycling of volatile sulfur, nitrogen and carbon compounds in aquatic environments. Mass spectrometers have become an invaluable tool in the laboratory research, as evidenced by the large number of research institutions with mass spectrometry core facilities. Yet, considerably fewer mass spectrometers are routinely used in the field, particularly on oceanographic expeditions. The PTR-MS system will provide an unparalleled ability to simultaneously measure parameters relating to the concentrations and fluxes of a number of ecologically and climatically important compounds such as carbon dioxide, methane, nitrous oxide and dimethylsulfide (DMS) onboard research ships and in remote field camps. The instrument will provide a novel and state-of-the-art research tool for undergraduate and graduate research.Ongoing studies point out that climate feedback mechanisms involving phytoplankton, DMS and cloud formation are poorly understand, which in turn hinders efforts to successfully model them. Refinement of many of the functional relationships in the oceanic DMS cycle is required to improve future models, including developing taxon-specific relationships. Similarly, the inability of current models to successfully and consistently reproduce some features of the cycle, such as the "summer DMS paradox", suggests that key processes may not be incorporated or accurately depicted in some models. The relative proportions of the cleavage of the oceanic precursor dimethylsulfoniopropionate (DMSP) to DMS or demethylation to other S-compounds are also thought to be an important control on DMS production, but the factors controlling these proportions remain unclear. Concurrently, changing global climate is expected to cause an array of physico-chemical responses in the world?s oceans that will have profound impact on marine phytoplankton communities both at a cellular level (physiologically) and at a community level (ecologically). The impacts could occur through changes in nutrient cycling, such as iron or nitrogen, or changes in abiotic factors that control phytoplankton growth, such as temperature and light. Depending on the taxa involved, the responses of the phytoplankton communities will impact both positively and negatively global biogeochemical cycles, including those of carbon, nitrogen and sulfur, and feedback mechanisms involving those elements. The PTR-MS system will be used to address a number of critical questions in the biogeochemical cycling of sulfur, nitrogen and carbon, including species-specific intracellular DMSP concentrations and biosynthesis rates, phytoplankton metabolomics, the role of vitamin B12 in the production of DMSP and the modulation of oceanic DMS levels, seawater ammonia concentrations and the coupling between oceanic DMS and ammonia emissions, and biogeochemical cycling in Antarctic lakes and sub-glacial environments. The results obtained from the PTR-MS system during these investigations will advance understanding of aquatic biogeochemical processes and provide critical information on the rates of formation (or degradation) of a number of biogeochemically important compounds and the relative importance of critical biogeochemical pathways, at both cellular and ecosystem levels. This data will help refine global biogeochemical and climate models.