Trace metal regulation of autotrophic and heterotrophic processes involved in the cycling of climate-active gases in the Subarctic Pacific and the Arctic Oceans

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Over much of the world's oceans, the supply of 'bioactive' trace metals such as iron (Fe) and copper (Cu) influences microbial processes that produce and consume climate-active gases (e.g. carbon dioxide, nitrous oxide and methane). Climate-dependent changes in ocean acidification and decreasing sub-surface oxygen levels are expected to alter Fe and Cu chemistry most dramatically, thus potentially affecting the rate of microbial gas cycling, leading to biogeochemical climate feedbacks. Although the biochemical roles of Fe in photosynthetic and heterotrophic metabolism are well established in a few individual species, and some information is available on Cu metabolism in diatoms (an ecologically important phytoplankton taxon) and denitrifiers, little is known about the physiology of Fe and Cu in many other bacteria and phytoplankton groups. Moreover, the response of marine microorganisms to climate related changes in trace metal availability is largely unexplored. This proposal seeks funds to investigate how altered oceanic pH and O2 levels will affect Fe and Cu bioavailability, and how these changes will influence the rate of key autotrophic and heterotrophic pathways (e.g. greenhouse gas cycling, trace metal transport, homeostasis,) by phytoplankton, as well as denitrifying and methane oxidizing bacteria. The proposed research program will integrate field-based and laboratory studies. Field investigations will be conducted in a) the NE Subarctic Pacific, a Fe poor region with acidified surface waters and an expanding sub-surface oxygen minimum zone, and b) the Arctic Ocean, an understudied region where ocean acidification and methane release are prominent. The proposed research will advance our fundamental knowledge of trace metal physiology in key marine microorganisms, with possible applications for environmental bioremediation. More broadly, understanding how trace elements control C and nutrient cycling in the Arctic and NE Pacific Oceans is essential to better predict climate change impacts on marine biogeochemical cycles, C sequestration capacity and sea-air gradients of 'climate active' gases.