Incorporation of Mg and Sr in calcite of cultured benthic foraminifera (Heterostegina depressa and Ammonia tepida) and seawater carbonate chemistry, 2010

DOI

We investigated the effect of the calcium concentration in seawater and thereby the calcite saturation state (omega) on the magnesium and strontium incorporation into benthic foraminiferal calcite under laboratory conditions. For this purpose individuals of the shallow-water species Heterostegina depressa (precipitating high-Mg calcite, symbiont-bearing) and Ammonia tepida (low-Mg calcite, symbiont-barren) were cultured in media under a range of [Ca2+], but similar Mg/Ca ratios. Trace element/Ca ratios of newly formed calcite were analysed with Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and normalized to the seawater elemental composition using the equation DTE=(TE/Cacalcite)/(TE/Caseawater). The culturing study shows that DMg of A. tepida significantly decreases with increasing omega at a gradient of -4.3x10-5 per omega unit. The DSr value of A. tepida does not change with omega, suggesting that fossil Sr/Ca in this species may be a potential tool to reconstruct past variations in seawater Sr/Ca. Conversely, DMg of H. depressa shows only a minor decrease with increasing omega, while DSr increases considerably with omega at a gradient of 0.009 per omega unit. The different responses to seawater chemistry of the two species may be explained by a difference in the calcification pathway that is, at the same time, responsible for the variation in the total Mg incorporation between the two species. Since the Mg/Ca ratio in H. depressa is 50-100 times higher than that of A. tepida, it is suggested that the latter exhibits a mechanism that decreases the Mg/Ca ratio of the calcification fluid, while the high-Mg calcite forming species may not have this physiological tool. If the dependency of Mg incorporation on seawater [Ca2+] is also valid for deep-sea benthic foraminifera typically used for paleostudies, the higher Ca concentrations in the past may potentially bias temperature reconstructions to a considerable degree. For instance, 25 Myr ago Mg/Ca ratios in A. tepida would have been 0.2 mmol/mol lower than today, due to the 1.5 times higher [Ca2+] of seawater, which in turn would lead to a temperature underestimation of more than 2 °C.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne and Gattuso, 2011) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI).

Supplement to: Raitzsch, Markus; Dueñas-Bohórquez, Adriana; Reichart, Gert-Jan; de Nooijer, Lennart Jan; Bickert, Torsten (2010): Incorporation of Mg and Sr in calcite of cultured benthic foraminifera: impact of calcium concentration and associated saturation state. Biogeosciences, 7(3), 869-881

Identifier
DOI https://doi.org/10.1594/PANGAEA.758073
Related Identifier https://doi.org/10.5194/bg-7-869-2010
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.758073
Provenance
Creator Raitzsch, Markus (ORCID: 0000-0003-4214-358X); Dueñas-Bohórquez, Adriana; Reichart, Gert-Jan ORCID logo; de Nooijer, Lennart Jan ORCID logo; Bickert, Torsten ORCID logo
Publisher PANGAEA
Contributor Nisumaa, Anne-Marin
Publication Year 2010
Funding Reference Seventh Framework Programme https://doi.org/10.13039/100011102 Crossref Funder ID 211384 https://cordis.europa.eu/project/id/211384 European Project on Ocean Acidification; Sixth Framework Programme https://doi.org/10.13039/100011103 Crossref Funder ID 511106 https://cordis.europa.eu/project/id/511106 European network of excellence for Ocean Ecosystems Analysis
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 304 data points
Discipline Earth System Research