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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.

Research article 19 Feb 2019

Research article | 19 Feb 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Environmental and biological controls on Na / Ca ratios in scleractinian cold-water corals

Nicolai Schleinkofer1, Jacek Raddatz1, André Freiwald2,3, David Evans1, Lydia Beuck2, Andres Rüggeberg4, and Volker Liebetrau5 Nicolai Schleinkofer et al.
  • 1Goethe University Frankfurt, Institute of Geosciences, Altenhöferallee 1, 60438 Frankfurt am Main, Germany
  • 2Senckenberg am Meer, Marine Research Department, Südstrand 40, 26382 Wilhelmshaven, Germany
  • 3MARUM (Zentrum für Marine Umweltwissenschaften), Bremen University, Leobener Str. 8, 28359 Bremen, Germany
  • 4Department of Geosciences, Faculty of Science and Medicine, University of Fribourg, Chemin du Musée 6, CH-1700 Fribourg, Switzerland
  • 5GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, D-24148 Kiel, Germany

Abstract. Here we present a comprehensive attempt to correlate aragonitic Na / Ca ratios from Lophelia pertusa, Madrepora oculata and a caryophylliid cold-water coral (CWC) species with different seawater parameters such as temperature, salinity and pH. Living CWC specimens were collected from 16 different locations and analyzed for their Na / Ca content using solution-based inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements. The results reveal no apparent correlation with salinity (30.1–40.57 g/kg) but a significant inverse correlation with temperature (−0.31 mmol/mol/°C). Other marine aragonitic organisms such as Mytilus edulis (inner aragonitic shell portion) and Porites sp. exhibit similar results highlighting the consistency of the calculated CWC regressions. Corresponding Na / Mg ratios show a similar temperature sensitivity to Na / Ca ratios, but the combination of two ratios appear to reduce the impact of vital effects and domain-dependent geochemical variation. The high degree of scatter and elemental heterogeneities between the different skeletal features in both Na / Ca and Na / Mg however limit the use of these ratios as a proxy and/or make a high number of samples necessary. Additionally, we explore two models to explain the observed temperature sensitivity of Na / Ca ratios for an open and semi-enclosed calcifying space based on temperature sensitive Na and Ca pumping enzymes and transport proteins that change the composition of the calcifying fluid and consequently the skeletal Na / Ca ratio.

Nicolai Schleinkofer et al.
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Nicolai Schleinkofer et al.
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Short summary
In this study we tried to correlate Na / Ca ratios from scleractinian cold-water corals with environmental parameters such as salinity, temperature and pH. We do not observe a correlation between Na / Ca ratios and seawater salinity but we do observe a strong correlation with temperature. Na / Ca data from warm-water corals (Porites spp.) and bivalves (Mytilus edulis) support this correlation, indicating that similar controls on the incorporation of sodium exist in these aragonitic organisms.
In this study we tried to correlate Na / Ca ratios from scleractinian cold-water corals with...