The isotopes of oxygen (16,17&18) have been utilized as tracers of marine biogeochemical processes impacting dissolved oxygen (O₂) since the 1970's, however it is only recently with the development of membrane inlet mass spectrometry (MIMS) that instrumentation was robust enough for at sea measurements. In this presentation we will give a brief overview of the current application of oxygen isotopes to biogeochemical processes of relevance to ocean deoxygenation:  sources (e.g. gross oxygen production (GOP) via photosynthesis) and sinks (e.g. community respiration). Data will be presented on GOP by picoplankton (Prochlorococcus and Synechococcus) cultures. Field work from a low oxygen environment (Lough Furnace, Ireland) also suggests that oxygen isotopes may help constrain oxygen fluxes and reveal interactions with nitrogen and sulfur biogeochemistry.  Oxygen isotopes are also applicable to reactions involving other Reactive Oxygen Species (ROS: O₂, O₂^- , H₂O₂ & OH) in seawater, ROS are important roles in phytoplankton health and in redox reactions with trace metals (e.g. Fe, Cu and Mn) and organic matter. Using this approach we employed H₂¹⁸O₂  with picoplankton cultures to quantify catalase and peroxidase activity in cells.  Picoplankton work was supported by the TRIATLAS project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 817578. Field work in Ireland was supported by the IMBER endorsed project NUTS&BOLTS, co-funded by EPA Research (2018-W-LS-19) and the Marine Institute. 

Primary Presenter: Peter Croot, University of Galway (croot.peter@gmail.com)

Authors:

Maija Heller, University of Galway  (maija.heller@marine.ie)