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| Titel |
Sediment chemoautotrophy in the coastal ocean |
| VerfasserIn |
Diana Vasquez-Cardenas, Filip J. R. Meysman, Peter van Breugel, Henricus T. S. Boschker |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130808
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| Publikation (Nr.) |
 EGU/EGU2016-11120.pdf |
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| Zusammenfassung |
| A key process in the biogeochemistry of coastal sediments is the reoxidation of reduced
intermediates formed during anaerobic mineralization which in part is performed by
chemoautotrophic micro-organisms. These microbes fix inorganic carbon using the energy
derived from reoxidation reactions and in doing so can fix up to 32% of the CO2 released by
mineralization. However the importance and distribution of chemoautotrophy has not been
systematically investigated in these environments. To address these issues we surveyed
nine coastal sediments by means of bacterial biomarker analysis (phospholipid
derived fatty acids) combined with stable isotope probing (13C-bicarbonate) which
resulted in an almost doubling of the number of observations on coastal sedimentary
chemoautotrophy.
Firstly, sediment chemoautotrophy rates from this study and rates compiled from literature
(0.07 to 36 mmol C m−2 d−1) showed a power-law relation with benthic oxygen uptake (3.4
to 192 mmol O2 m−2 d−1). Benthic oxygen uptake was used as a proxy for carbon
mineralization to calculate the ratio of the CO2 fixed by chemoautotrophy over the total CO2
released through mineralization. This CO2 efficiency was 3% in continental shelf, 9% in
nearshore and 21% in salt marsh sediments. These results suggest that chemoautotrophy
plays an important role in C-cycling in reactive intertidal sediments such as salt marshes
rather than in the organic-poor, permeable continental shelf sediments. Globally in the coastal
ocean our empirical results show that chemoautotrophy contributes ∼0.05 Pg C y−1 which is
four times less than previous estimates.
Secondly, five coastal sediment regimes were linked to the depth-distribution of
chemoautotrophy: 1) permeable sediments dominated by advective porewater transport, 2)
bioturbated sediments, and cohesive sediments dominated by diffusive porewater
transport characterized by either 3) canonical sulfur oxidation, 4) nitrate-storing
Beggiatoa, or 5) electrogenic sulfur oxidation. Sediments with an O2-H2S interface
exhibited highest chemoautotrophy activity in the top centimeter via canonical
sulfur oxidation, whereas in the presence of electrogenic sulfur oxidation a uniform
distribution of chemoautotrophy throughout the top centimeters of the sediment was
evidenced. Lowest dark carbon fixation was found in permeable advective-driven
sediments with deep oxygen penetration resulting in higher subsurface than surface
activity. Hence, the depth-distribution of chemoautotrophy in coastal sediments
varies due to several biogeochemical characteristics such as grain size, organic
carbon content, presence of filamentous sulfur oxidizing bacteria, and macrofaunal
activity. |
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