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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2020-206
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-206
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 30 Jun 2020

Submitted as: research article | 30 Jun 2020

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This preprint is currently under review for the journal BG.

Monsoonal forcing controlled cold water coral growth off south-eastern Brazil during the past 160 kyrs

André Bahr1, Monika Doubrawa1,2, Jürgen Titschack3,4, Gregor Austermann1, Dirk Nürnberg5, Ana Luiza Albuquerque6, Oliver Friedrich1, and Jacek Raddatz7 André Bahr et al.
  • 1Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany
  • 2Earth and Environmental Sciences,KU Leuven, Celestijnenlaan 200e, 3001 Leuven, Belgium
  • 3MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str. 8, 28359 Bremen, Germany
  • 4Senckenberg am Meer, Marine Research Department, 26382 Wilhelmshaven, Germany
  • 5GEOMAR Helmholtz Centre for Ocean Research, Wischhofstraße 1-3, 24148 Kiel, Germany
  • 6Departamento de Geoquímica, Universidade Federal Fluminense, Outeiro São João Baptista s/n. – Centro, Niterói, RJ, Brazil
  • 7Institute of Geosciences, Goethe University, Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany

Abstract. Cold-water corals (CWC) constitute important deep-water ecosystems that are increasingly under environmental pressure due to ocean acidification and global warming. The sensitivity of these deep-water ecosystems to environmental change is demonstrated by abundant paleo-records drilled through CWC mounds that reveal a characteristic alteration between rapid formation and dormant or erosive phases. Previous studies have identified several parameters such as food supply, oxygenation, and carbon saturation state of bottom water as central for driving or inhibiting CWC growth, yet there is still a large uncertainty about the relative importance of the different environmental parameters. To advance this debate we have performed a multi-proxy study on a sediment core retrieved from the 25 m high Bowie Mound, located in 866 m water depth on the continental slope off south-eastern Brazil, a structure built up mainly by the CWC Solenosmilia variabilis. Our results indicate a multi-factorial control on CWC growth and mound formation at Bowie Mound during the past ~160 kyrs, which reveals distinct formation pulses during glacial high northern latitude cold events (Heinrich Stadials, HS) largely associated with anomalous continental wet periods. The ensuing enhanced run-off elevated the terrigenous nutrient and organic matter supply to the continental margin, and might have boosted marine productivity. The dispersal of food particles towards the CWC colonies during HS was facilitated by the highly dynamic hydraulic conditions along the continental slope that prevailed throughout glacial periods. These conditions caused the emplacement of a pronounced nepheloid layer above Bowie Mound aiding the concentration and along-slope dispersal of organic matter. Our study thus demonstrates a yet unrecognized impact of continental climate variability on a highly vulnerable deep-marine ecosystem.

André Bahr et al.

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André Bahr et al.

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Short summary
We explore the sensitivity of cold-water corals (CWC) to environmental changes utilizing a multi-proxy approach on a coral-bearing sediment core from off south-eastern Brazil. Our results reveal that over the past 160 kyrs CWCs flourished during glacial high northern latitude cold events (Heinrich Stadials). These periods were associated with anomalous wet phases on the continent enhancing terrigenous nutrient and organic matter supply to the continental margin, boosting food supply to the CWC.
We explore the sensitivity of cold-water corals (CWC) to environmental changes utilizing a...
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