Deciphering the composition and fate of dissolved organic matter in a rapidly changing Arctic Ocean

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Marine dissolved organic matter (DOM) is central to the current and future global carbon cycle, with a reservoir comparable in size to the current atmospheric carbon dioxide reservoir. The fact that the oceans are a huge reservoir of carbon has continued to urge scientists to investigate what DOM is in terms of its source, chemical composition, reactivity and function in marine environments for decades. Marine DOM originates from marine primary production, however only a small fraction is identifiable as common molecules. My research program aims to elucidate the composition and dynamics of dissolved organic matter in marine ecosystems. During the next five years, I plan to continue my research program on the cycling and dynamics of DOM in the highly stratified Arctic's Canada Basin. Specifically, the main objectives will be to: 1)Link fluorescence properties of marine DOM to identifiable molecules. Excitation emission matrix spectroscopy associated with Parallel Factor Analysis (EEM-PARAFAC) has been applied to gain insights about the distribution and dynamics of protein-like and humic-like DOM but there is still a lack of direct evidence linking PARAFAC components to molecularly characterized molecules. Concurrent determination of fluorescence composition, lignin phenol, carbohydrates and amino acids will be used to investigate the relationships between specific fluorescent components and identifiable molecules. 2)Assess the refractory nature of DOM. Mesocosm experiments will be conducted aboard the Canadian Coast Guard icebreaker to assess how the bulk and molecular composition of DOM changes over time, and with changes in bacteria taxonomy. Our research aims to illuminate dark-ocean organic biogeochemistry that is crucial for understanding the cycling of DOM in the global ocean. 3)Investigate the seasonal dynamics of DOM in the Arctic Ocean. High frequency measurements from in situ fluorescent DOM sensors will expand our observations spatially and seasonally. The temporal variability in DOM fluorescence will be related to the change in stratification, biological activities, mineralization and ice cover. This research program will allow to better understand the composition, source and dynamics of DOM in marine waters. The 19 HQP involved in this program would also have the unique opportunity to work in the Canadian Arctic where rapid environmental changes are occurring. The skills and knowledge gained within this project, including cutting edge analytical techniques, arctic experience and intercultural and leadership skills will be invaluable in careers in academia, government or industry.