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Biogeosciences An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 20 May 2019

Submitted as: research article | 20 May 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Biogeosciences (BG).

Bottom-water deoxygenation at the Peruvian Margin during the last deglaciation recorded by benthic foraminifera

Zeynep Erdem1, Joachim Schönfeld2, Anthony E. Rathburn3, Maria-Elena Pérez4, Jorge Cardich5, and Nicolaas Glock2 Zeynep Erdem et al.
  • 1NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University, P.O. Box 59, 1790 AB Den Burg, Texel, the Netherlands
  • 2GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, 24148, Kiel, Germany
  • 3Department of Geological Sciences, California State University, Bakersfield, CA, 93311, USA
  • 4Natural History Museum, Department of Palaeontology, London, UK
  • 5Instituto del Mar del Peru (IMARPE), A. Gamarra y Gral. Valle, Chucuito, Callao 01, Peru

Abstract. Deciphering the dynamics of dissolved oxygen in the mid-depth ocean during the last deglaciation is essential to understand the influence of climate change on modern oxygen minimum zones (OMZs). Many paleo-proxy records from the Eastern Pacific Ocean indicate an extension of oxygen depleted conditions during the deglaciation but the degree of deoxygenation has not been quantified to date. The Peruvian OMZ, one of the largest OMZs in the world, is a key area to monitor such changes in near-bottom water oxygenation in relation to changing climatic conditions. Here, we analysed the potential to use the composition of foraminiferal assemblages from the Peruvian OMZ as a quantitative redox-proxy. A multiple regression analysis was applied to a joint dataset of living (rose Bengal stained, fossilizable calcareous species) benthic foraminiferal distributions from the Peruvian continental margin. Bottom-water oxygen concentrations ([O2]BW) during sampling were used as dependant variable. The correlation was significant (R2 = 0.82; p < 0.05) indicating that the foraminiferal assemblages are rather governed by oxygen availability than by the deposition of particulate organic matter (R2 = 0.53; p = 0.31). We applied the regression formula to four sediment cores from the northern part of the Peruvian OMZ between 3° S and 8° S and 600 m to 1250 m water depths; thereby recording oxygenation changes at the lower boundary of the Peruvian OMZ. Each core displayed a similar trend of decreasing oxygen levels since the Last Glacial Maximum (LGM). The overall [O2]BW change from the Last Glacial Maximum and the Holocene was constrained to 30 μmol/kg at the lower boundary of the OMZ, whereas at shallower depths [O2]BW was relatively stable along the deglaciation. The deoxygenation trend was time-transgressive. It commenced at the southern core, and gradually spread to deeper waters and to the northernmost core location. This pattern indicates a gradual expansion of the OMZ during the last deglaciation, as a result of increasing surface productivity in the Eastern Equatorial Pacific and decreasing advective oxygen supply to intermediate waters off Peru.

Zeynep Erdem et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Zeynep Erdem et al.
Data sets

Peruvian Margin living benthic foraminiferal distributions in percentages Z. Erdem, J. Schönfeld, A. E. Rathburn, M.-E. Pérez, J. Cardich, and N. Glock

Zeynep Erdem et al.
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Short summary
Recent observations from today’s oceans revealed that oxygen concentrations are decreasing, and oxygen minimum zones are expanding together with current climate change. With the aim of understanding past climatic events and its relationship with oxygen content we looked at the fossils, called benthic foraminifera, preserved in the sediment archives from Peruvian margin and quantified the bottom water oxygen content for the last 22 thousand years.
Recent observations from today’s oceans revealed that oxygen concentrations are decreasing,...