Abstract
The degradation of sedimentary particulate organic carbon (POC) is a key carbon cycle process that fuels the deep subseafloor biosphere. The reactivity of POC is expected to decrease with increasing sediment age, severely restricting the energy available to microorganisms. Conversely, increasing temperatures during burial have been proposed to stimulate POC degradation, possibly supplying significant energy to the deep biosphere. To test the importance of temperature, we assembled POC measurements in two global sets of drill sites where sediments underwent either relatively low or high temperatures during burial, which should have resulted in different rates of POC degradation. For ages 5–10 Ma, the decrease of the average POC content with burial is clearly more pronounced in the sites with high temperature histories. Our results support the hypothesis that temperature is one of the fundamental controls on the rate of POC degradation within deeply buried marine sediments.
Highlights
Has been suggested that methane must have migrated upward from deep sources[21]
Reaction-transport modeling shows that observed methane hydrate occurrences can be explained by deep particulate organic carbon (POC) degradation driven by increasing temperature[24] and suggests that higher ocean temperatures in the Paleogene enhanced microbial methane production, building up a sizable global gas hydrate reservoir[25]
We take a different approach from previous studies, which focused on experiments at laboratory time scales and on observations and modeling at a few sites, by looking at a large global data set of POC, temperature, and sediment age collected in deep sediments by scientific ocean drilling
Summary
Has been suggested that methane must have migrated upward from deep sources[21] Methane in these hydrate deposits is typically microbial, and it is unclear how it could be generated at substantial depths if POC reactivity steadily decreases with increasing age. Others found that including the temperature effect resulted in modeled concentrations of dissolved metabolites (inorganic carbon and ammonium) higher than those observed[15]. These authors concluded that temperature does not significantly affect POC degradation in deeply buried sediments, perhaps because the succession of microorganisms in the sediment column have adapted to the local temperature. The POC decrease with age should be more pronounced in locations where temperatures were higher during burial and degradation rates were faster
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
