Triple oxygen isotopes of respiration and photo-oxidation of DOC

The biogeochemical fluxes that cycle oxygen (O2) play a critical role in regulating Earth's climate and habitability. Triple-oxygen isotope (TOI) compositions of marine dissolved O2 are considered a robust tool for tracing oxygen cycling and quantifying gross photosynthetic O2 production. This method assumes that photosynthesis, microbial respiration, and gas exchange with the atmosphere are the primary influences on dissolved O2 content, and that they have predictable, fixed isotope effects. Despite its widespread use, there are major elements of this approach that remain uncharacterized, including the TOI dynamics of respiration by marine heterotrophic bacteria and abiotic O2 sinks such as the photochemical oxidation of dissolved organic carbon (DOC). Here, we report the TOI fractionation for O2 utilization by two model marine heterotrophs (Vibrio harveyi and Ruegeria pomeroyi DSS-3) and by abiotic photo-oxidation of representative terrestrial and coastal marine DOC. These data are described further in the related publication, Sutherland et al., 2022 (doi: 10.1093/pnasnexus/pgac233).