High frequency organic carbon and oxygen measurement reveal variability in respiratory quotients

The respiratory quotient (RQ), defined as the ratio of oxygen consumed to organic carbon removed during organic matter remineralization, is a critical metric for understanding organic carbon flux and storage in the ocean. Traditional oceanographic studies often rely on a fixed RQ value (~1.4), based on Redfield stoichiometry. However, recent research reveals considerable variability in RQs associated with dissolved organic matter, with values ranging from 0.3 to over 3.1. Constraining this variability is essential for accurately modeling organic carbon and oxygen dynamics in marine systems. Using high-frequency measurements of dissolved organic carbon (DOC) and oxygen in mixed culture bioassays, we detected shifts in RQs that may reflect changes in bacterial community composition, organic matter composition, and dominant metabolic pathways. Our results demonstrate dynamic temporal changes in RQs, often obscured by lower-frequency sampling methods. Here, we present our high-frequency sampling methodology and highlight how heterotrophic bacterioplankton dynamics influence RQ variability. These findings highlight the role of environmental and biological factors in shaping RQs and offer new insights into organic carbon and oxygen cycles in marine ecosystems.

Presentation Preference: Poster

Primary Presenter: Rachel Sandquist, University of California at Santa Barbara (rasandquist@ucsb.edu)

Authors:

Rachel Sandquist, University of California at Santa Barbara  (rasandquist@ucsb.edu)

Keri Opalk, University of California at Santa Barbara  (keri.opalk@ucsb.edu)

Craig Carlson, University of California at Santa Barbara  (craig_carlson@ucsb.edu)