Articles | Volume 10, issue 10
Biogeosciences, 10, 6185–6198, 2013
Biogeosciences, 10, 6185–6198, 2013

Research article 01 Oct 2013

Research article | 01 Oct 2013

Effect of ocean acidification on the benthic foraminifera Ammonia sp. is caused by a decrease in carbonate ion concentration

N. Keul*,1, G. Langer2, L. J. de Nooijer3, and J. Bijma4,1 N. Keul et al.
  • 1Alfred Wegener Institute, Am Handelshafen 12, Bremerhaven, 27570, Germany
  • 2Department of Earth Sciences, Cambridge University, Cambridge, CB2 3EQ, UK
  • 3Department of Marine Geology, Royal Netherlands Institute of Sea Research, Landsdiep 4, 1979 SZ, 't Horntje, the Netherlands
  • 4Jacobs University, Earth and Space Sciences, Campus Ring 8, Bremen, 28759, Germany
  • *now at: Lamont-Doherty Earth Observatory, Geosciences, Columbia University, 61 Rd 9W Palisades, NY 10964, USA

Abstract. About 30% of the anthropogenically released CO2 is taken up by the oceans; such uptake causes surface ocean pH to decrease and is commonly referred to as ocean acidification (OA). Foraminifera are one of the most abundant groups of marine calcifiers, estimated to precipitate ca. 50 % of biogenic calcium carbonate in the open oceans. We have compiled the state of the art literature on OA effects on foraminifera, because the majority of OA research on this group was published within the last three years. Disparate responses of this important group of marine calcifiers to OA were reported, highlighting the importance of a process-based understanding of OA effects on foraminifera. We cultured the benthic foraminifer Ammonia sp. under a range of carbonate chemistry manipulation treatments to identify the parameter of the carbonate system causing the observed effects. This parameter identification is the first step towards a process-based understanding. We argue that [CO32−] is the parameter affecting foraminiferal size-normalized weights (SNWs) and growth rates. Based on the presented data, we can confirm the strong potential of Ammonia sp. foraminiferal SNW as a [CO32−] proxy.

Final-revised paper