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SUMMARY:The effect of future warming on carbon remineralization by iron- a
 nd sulfate-reducing bacteria in sediments of a glaciated Arctic fjord
DTSTART:20250723T111500Z
DTEND:20250723T123000Z
DTSTAMP:20260608T020600Z
UID:indico-event-805@events.geomar.de
CONTACT:office-fb2@geomar.de
DESCRIPTION:Speakers: Katja Laufer-Meiser (Marine Geosystems)\n\nWilsterma
 nn C.\, Wunder L.C.\, Friedrich M.W.\, Schmidt M.\, Michaud A. B.\, Perner
  M.\, Laufer-Meiser K.\nAbstract\nSediments of glaciated fjords are biogeo
 chemical active interfaces connecting the cryosphere and terrestrial ecosy
 stems with the open ocean. They are hotspots of carbon burial and especial
 ly prone to climate change. Due to the Arctic amplification\, they are war
 ming faster than most other areas on Earth\, with yet mostly unknown conse
 quences for sediment biogeochemistry. Microbial iron and sulfate reduction
  are typically the most important processes for anaerobic carbon remineral
 ization in these sediments. We conducted anoxic microcosm incubations with
  sediment from Kongsfjorden\, Svalbard\, (114 m water depth) to identify m
 icroorganisms involved in these processes via RNA stable isotope probing (
 RNA-SIP). To simulate the effect of future warming\, incubations were done
  at 4°C (current temperature) and 12°C (expected in 50 years). We added 
 either 13C- or 12C-acetate (500 µM) and to some treatments also ferrihydr
 ite (5 mM) and/or molybdate (20 mM). Over time of incubation\, we followed
  concentrations of dissolved and solid-phase Fe\, H2S\, and measured sulfa
 te-reduction rates (SRR) with a 35S-SO42- tracer. We furthermore followed 
 the δ13C signal of CO2 in the headspace to confirm the utilization of the
  added acetate.\nOur results show that the addition of acetate stimulated 
 sulfate reduction\, with SRR approximately three times higher than the una
 mended control. During the 15-day incubations\, at 4°C SRR remained at th
 e same level\, while at 12°C SRR continuously increased and were about 10
 -times higher at the end. The addition of ferrihydrite stimulated iron red
 uction\, indicated by the decrease of poorly crystalline ascorbate-extract
 able Fe(III) over time. However\, the corresponding increase in dissolved 
 Fe(II) was only minor. Together with undetectable H2S and the measured SRR
 \, this indicates a close interplay of iron and sulfur cycles in this syst
 em. Results from RNA-SIP show that Arcobacteraceae are predominately respo
 nsible for Fe reduction at 4°C while Colwelliaceae predominate at 12°C. 
 Surprisingly\, classical sulfate reducing bacteria had a reduced abundance
  in the heavy fractions compared to the 12C control\, also when SRR were i
 ncreasing. The results highlight the sensitivity of the bacterial communit
 y and their associated metabolic processes towards warmer temperatures and
  that this has the potential to change the biogeochemistry of fjord sedime
 nts.\n\nhttps://events.geomar.de/event/805/
LOCATION:8A-002 - Hörsaal Ostufer / Lecture Hall East (GEOMAR - Standort 
 Ostufer  / GEOMAR - East Shore)
URL:https://events.geomar.de/event/805/
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