Microbial Responses to Ocean Deoxygenation

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The oceans are losing oxygen as the combined result of warming climate and increasing nutrient fluxes from land. Direct impacts of deoxygenation will be felt most acutely by marine organisms that will face challenges related to diminished respiration, habitat compression and loss, immune suppression, impaired reproduction, increased disease and mortality, and reduced growth. Indirect effects extend to life on land and include climate feedbacks and altered biogeochemical cycles. For humans, direct affects come from the vulnerability of the world's fisheries to deoxygenation, which thus poses serious risks to global food security. The specific impacts of ocean deoxygenation, however, will be strongly influenced by marine microorganisms and their responses to declining oxygen. These responses are highly uncertain, and thus so too is our ability to forecast and manage the impacts of ocean deoxygenation. The proposed research will couple state-of-the-art geochemical and microbiological analyses to determine microbial responses to deoxygenation in the epicenter of ocean oxygen loss-the North-Eastern Sub-Arctic Pacific ocean (NESAP). The NESAP is the oceanographic province with the most intense oxygen loss, and the core of the NESAP oxygen minimum zone is nearing a tipping point, at which anaerobic microbial metabolisms will engage. The NESAP is an ideal province in which to define microbial responses to deoxygenation, since a range of oxygenation states can be found both vertically as a function of depth, and laterally with distance off-shore. The NESAP can be accessed from the BC coast and through time-series experiments, which also house a rich archive of historical data. The proposed research will augment these time-series experiments with analyses designed to: 1) quantitatively determine the physiological response of marine bacteria to declining oxygen; 2) determine how oxygen availability influences trophic structure at the base of the marine food web; 3) determine the response of nutrient cycling in the NESAP to declining oxygen; and 4) reconstruct historical oxygenation states in the NESAP. The outcomes of the proposed research will include qualitative and quantitative models that describe microbial responses to ocean deoxygenation to enable better predictions of future deoxygenation and its impacts. This information is critical for the management of Canadian fisheries with implications for food security and responses to climate change. Through interactions and briefings to Department of Fisheries and Oceans, this research will inform future management policy. Beyond fisheries policy, information on microbial oxygen metabolism is more broadly extensible across sectors where microbial oxygen control can be leveraged for better health and process outcomes. Importantly, the proposed research will lead to 2 newly minted HQP with transdisciplinary expertise poised to tackle problems across multiple sectors.