Preprints
https://doi.org/10.5194/bg-2021-74
https://doi.org/10.5194/bg-2021-74

  29 Mar 2021

29 Mar 2021

Review status: this preprint is currently under review for the journal BG.

Host influenced geochemical signature in the parasitic foraminifer Hyrrokkin sarcophaga

Nicolai Schleinkofer1,2, David Evans1,2, Max Wisshak3, Janina Vanessa Büscher4,5, Jens Fiebig1,2, André Freiwald3, Sven Härter1, Horst R. Marschall1,2, Silke Voigt1,2, and Jacek Raddatz1,2 Nicolai Schleinkofer et al.
  • 1Goethe Universität Frankfurt, Institut für Geowissenschaften, Frankfurt am Main, Germany
  • 2Goethe Universität Frankfurt, Frankfurt Isotope and Element Research Center (FIERCE), Frankfurt am Main, Germany
  • 3Senckenberg am Meer, Marine Research Department, Wilhelmshaven, Germany
  • 4National University of Ireland Galway, Department of Earth and Ocean Sciences, Galway, Ireland
  • 5GEOMAR Helmholtz Centre for Ocean Research Kiel, Department of Biological Oceanography, Kiel, Germany

Abstract. Hyrrokkin sarcophaga is a parasitic foraminifer that is commonly found in cold-water coral reefs where it infests the file clam Acesta excavata and the scleractinian coral Lophelia pertusa. Here, we present measurements of the elemental and isotopic composition of this parasitic foraminifer for the first time, analyzed by inductively coupled optical emission spectrometry (ICP-OES), electron probe micro analysis (EPMA) and mass spectrometry (MS).

Our results reveal that the geochemical signature of H. sarcophaga depends on the host organism it infests. Sr/Ca ratios are 1.1 mmol mol−1 higher in H. sarcophaga that infest L. pertusa, which could be an indication that dissolved host carbonate material is utilised in shell calcification, given that the aragonite of L. pertusa has a naturally higher Sr concentration compared to the calcite of A. excavata. Similarly, we measure 3.1 ‰ lower δ13C and 0.25 ‰ lower δ18O values in H. sarcophaga that lived on L. pertusa, which might be caused by the direct uptake of the host's carbonate material with a more negative isotopic composition or different pH regimes in these foraminifera (pH can exert a control on the extent of CO2 hydration/hydroxylation) due to the uptake of body fluids of the host. We also observe higher Mn/Ca ratios in foraminifers that lived on A. excavata but did not penetrate the host shell compared to specimen that penetrated the shell, which could be interpreted as a change in food source, changes in the calcification rate, Rayleigh fractionation or changing oxygen conditions.

While our measurements provide an interesting insight into the calcification process of this unusual foraminifer, these data also indicate that the geochemistry of this parasitic foraminifer is unlikely to be a reliable indicator of paleoenvironmental conditions using Sr/Ca, Mn/Ca, δ18O or δ13C unless the host organism is known and its geochemical composition can be accounted for.

Nicolai Schleinkofer et al.

Status: open (until 10 May 2021)

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  • RC1: 'Comment on bg-2021-74', Lennart de Nooijer, 12 Apr 2021 reply

Nicolai Schleinkofer et al.

Nicolai Schleinkofer et al.

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Short summary
We have measured the chemical composition of the carbonate shells of the parasitic Foraminifera Hyrrokkin sarcophaga, in order to test if it is influenced by the host organism (bivalve or coral). We find that both the chemical and isotopic composition is influenced by the host organism. For example strontium is enriched in Foraminifera that grew on corals, whose skeleton is built from aragonite which is naturally enriched in strontium compared to the bivalves calcite shell.
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