EGU21-1837
https://doi.org/10.5194/egusphere-egu21-1837
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Impact of Thiomargarita on the rates of N, S and P turnover in mudbelt sediments from the Benguela Upwelling System: a model study

Pei-Chuan Chuang1, Matthias Zabel2, Stefan Sommer1, Florian Scholz1, Paul Vosteen1, and Andrew W. Dale1
Pei-Chuan Chuang et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1–3, 24148 Kiel, Germany
  • 2MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str., 28359 Bremen, Germany

The availability of major nutrients, nitrogen (N) and phosphorus (P), largely controls primary productivity in eastern boundary upwelling systems. The oxygen minimum zone (OMZ) on the Namibian shelf is characterized by high productivity and extraordinarily high particulate organic carbon (POC) contents (up to 19 % dry weight) in the surface sediments. The anaerobic degradation of POC by bacterial sulfate reduction leads to the production of hydrogen sulfide (H2S) that supports extensive communities of large sulfur bacteria Thiomargarita namibiensis in surface shelf sediments. These bacteria oxidize sulfide by reducing nitrate (NO3-) to either ammonium (NH4+) or dinitrogen (N2). Thiomargarita also affect phosphorus cycling by intracellular incorporation of polyphosphates and extracellular formation of hydroxyapatites. In order to understand and quantify the complexity of the coupled benthic cycles of C, N, P, S, Fe in the Benguela Upwelling System, a reaction-transport model (RTM) was used to simulate sediment biogeochemical data collected from the RV Meteor cruise (M157, August 4th-September 16th 2019) off Namibia. This allowed deeper insights into the role of sulfur-oxidizing bacteria on P and N fluxes across the sediment surface. Results are presented that point toward potentially strong feedbacks by Thiomargarita on primary production in response to ongoing global warming and ocean deoxygenation.

How to cite: Chuang, P.-C., Zabel, M., Sommer, S., Scholz, F., Vosteen, P., and Dale, A. W.: Impact of Thiomargarita on the rates of N, S and P turnover in mudbelt sediments from the Benguela Upwelling System: a model study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1837, https://doi.org/10.5194/egusphere-egu21-1837, 2021.

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