Preprints
https://doi.org/10.5194/egusphere-2024-3636
https://doi.org/10.5194/egusphere-2024-3636
03 Dec 2024
 | 03 Dec 2024

Brief Communications: Stream Microbes Preferentially Utilize Young Carbon within the Ancient Bulk Glacier Dissolved Organic Carbon Pool

Amy D. Holt, Jason B. Fellman, Anne M. Kellerman, Eran Hood, Samantha H. Bosman, Amy M. McKenna, Jeffery P. Chanton, and Robert G. M. Spencer

Abstract. Glaciers export ancient, bioavailable dissolved organic carbon (DOC). Yet, the sources of organic carbon (OC) underpinning bioavailability are poorly constrained. We assessed the isotopic composition of respired OC from bioincubations of glacier DOC. Relative to DOC, respired OC was younger (+4,350 – 8,940 yBP) and 13C enriched (+9.2 – 12.2 ‰), consistent with utilization of an in situ produced microbial carbon source. Molecular-level analyses suggest respired OC was associated with the aliphatic-rich portion of the dissolved organic matter pool. These findings provide direct evidence that a hidden pool of young OC may underpin the high bioavailability of ancient glacier DOC.

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Glacier runoff is a source of old, bioavailable dissolved organic carbon (DOC) to downstream...
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