Abstract
Previously, we presented data that indicated microbial sulfide oxidation would out-compete strictly chemical, abiotic sulfide oxidation reactions under nearly all conditions relevant to extant ecosystems (Luther et al., 2011). In particular, we showed how anaerobic microbial sulfide oxidation rates were several orders of magnitude higher than even metal catalyzed aerobic sulfide oxidation processes. The fact that biotic anaerobic sulfide oxidation is kinetically superior to abiotic reactions implies that nearly all anaerobic and sulfidic environments should host microbial populations that oxidize sulfide at appreciable rates. This was likely an important biogeochemical process during long stretches of euxinia in the oceans suggested by the geologic record. In particular, phototrophic sulfide oxidation allows the utilization of carbon dioxide as the electron acceptor suggesting that this process should be particularly widespread rather than relying on the presence of other chemical oxidants. Using the Chesapeake Bay as an example, we argue that phototrophic sulfide oxidation may be more important in many environments than is currently appreciated. Finally, we present methodological considerations to assist other groups that wish to study this process.
Highlights
The accumulation of molecular oxygen in Earth’s biosphere was not instantaneous with the onset of oxygenic photosynthesis
We provide technical details on one method for measuring phototrophic dependent sulfide oxidation
Our goal is to provide a solid technical foundation for others that wish to make similar measurements and allow them to benefit from our experiences in setting up these types of experimental rigs
Summary
The accumulation of molecular oxygen in Earth’s biosphere was not instantaneous with the onset of oxygenic photosynthesis. It is thought to have occurred over billions of years and not necessarily as a smooth gradual progression of O2 concentrations, but as a series of at least two steps (Scott et al, 2008; Frei et al, 2009; Farquhar et al, 2011). Substantial reservoirs of reduced chemical species (i.e., Fe2+and HS−) are thought to have existed in early oceans and these would have to be oxidized prior to the full oxygenation of the oceans. As O2 production is light dependent, ocean oxygenation and oxidation was most likely a top down process, i.e., shallow layers with highest oxygen production rates would have become oxygenated more rapidly over time than deep water layers (Figure 1). The Archaean ocean was ferruginous with low sulfur concentrations (Canfield et al, 2000). The initial rise of oxygen in the atmosphere increased continental weathering www.frontiersin.org
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