Uncovering the role of oxygen on organic carbon cycling: insights from a continuous culture study with a facultative anaerobic bacterioplankton species (Shewanella baltica)

Deoxygenation is tied to organic carbon (C org ) supply and utilization in marine systems. Under oxygen-depletion, bacteria maintain C org respiration using alternative electron acceptors such as nitrate. Since anaerobic respiration’s energy yield is lower, C org remineralization may be reduced and its residence time increased. We investigated the influence of oxygen and alternative electron acceptors’ availability on C org cycling by heterotrophic bacteria during a continuous culture experiment with Shewanella baltica , a facultative anaerobic γ-Proteobacteria in the Baltic Sea. We tested six different oxygen levels, from suboxic (