Microbial carbon cycling in marine environments: linking micro-scale processes to global carbon dynamics

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The ocean is home to complex and diverse microorganisms that shape the dynamics of these ecosystems in a myriad of ways. Through their metabolism and growth, marine microorganisms play a central role in the global carbon cycle and influence the size and magnitude of carbon that becomes sequestered in deep ocean waters and sediments. My research focuses on heterotrophic microorganisms which break down organic carbon and release carbon dioxide (CO2) as a byproduct of their metabolism, this is referred to as the remineralization of organic matter. Heterotrophic microorganisms are the primary producers of CO2 in the ocean and any substantial change in their metabolic activity has the potential to significantly alter how carbon is processed and stored in the ocean. The proposed research will use a variety of molecular and isotopic tools to gain new insights into the controls on heterotrophic microorganisms as well as the metabolic pathways and ecological interactions that underpin carbon cycling in the ocean. The core research questions are: 1) how does the metabolic potential of microorganisms influence organic matter remineralization? (2) do ecological interactions between microorganisms increase or decrease rates of organic matter remineralization? and (3) is cell density an important control on the production of enzymes that initiate the remineralization of organic matter? These questions will be examined through three testable hypotheses in studies conducted by two MSc students, two PhD students and four undergraduate students. Overall the results of this research will advance our understanding of the microbial mechanisms that regulate carbon fluxes in the ocean. Ultimately, this will allow us to develop a much needed molecular-level framework to improve our ability to predict how marine carbon cycling will change under a future warmer climate. Additionally, microorganisms play a direct role in remediating spilled oil in the ocean. Deciphering the fundamental mechanisms that regulate microbial activity will greatly improve our ability to develop oil spill response plans and remediation strategies. This research program will maintain and build Canada's profile in this critical field of research, especially as global climate change threatens the health of our oceans. I have played a leading role in establishing new research tools that aim to understand the interactions between microorganisms and organic carbon. My interdisciplinary background in the fields of isotope geochemistry, molecular biology and microbiology, make me uniquely qualified to lead the proposed research program.