Temperature and carbonate ion effects on Mg/Ca and Sr/Ca ratios in benthic foraminifera : aragonitic species Hoeglundina elegans
Lear, Caroline H.
Oppo, Delia W.
Linsley, Braddock K.
MetadataShow full item record
Core top samples from Atlantic (Little Bahama Banks (LBB)) and Pacific (Hawaii and Indonesia) depth transects have been analyzed in order to assess the influence of bottom water temperature (BWT) and aragonite saturation levels on Mg/Ca and Sr/Ca ratios in the aragonitic benthic foraminifer Hoeglundina elegans. Both the Mg/Ca and Sr/Ca ratios in H. elegans tests show a general decrease with increasing water depth. Although at each site the decreasing trends are consistent with the in situ temperature profile, Mg/Ca and Sr/Ca ratios in LBB are substantially higher than in Indonesia and Hawaii at comparable water depths with a greater difference observed with increasing water depth. Because we find no significant difference between results obtained on “live” and “dead” specimens, we propose that these differences are due to primary effects on the metal uptake during test formation. Evaluation of the water column properties at each site suggests that in situ CO3 ion concentrations play an important role in determining the H. elegans Mg/Ca and Sr/Ca ratios. The CO3 ion effect is limited, however, only to aragonite saturation levels ([ΔCO3]aragonite) below 15 μmol kg−1. Above this level, temperature exerts a dominant effect. Accordingly, we propose that Mg/Ca and Sr/Ca in H. elegans tests can be used to reconstruct thermocline temperatures only in waters oversaturated with respect to the mineral aragonite using the following relationships: Mg/Ca = (0.034 ± 0.002)BWT + (0.96 ± 0.03) and Sr/Ca = (0.060 ± 0.002)BWT + (1.53 ± 0.03) (for [ΔCO3]aragonite > 15 μmol kg−1). The standard error associated with these equations is about ±1.1°C. Reconstruction of deeper water temperatures is complicated because in undersaturated waters, changes in Mg/Ca and Sr/Ca ratios reflect a combination of changes in [CO3] and BWT. Overall, we find that Sr/Ca, rather than Mg/Ca, in H. elegans may be a more accurate proxy for reconstructing paleotemperatures.
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 21 (2006): PA1007, doi:10.1029/2005PA001158.
Suggested CitationArticle: Rosenthal, Yair, Lear, Caroline H., Oppo, Delia W., Linsley, Braddock K., "Temperature and carbonate ion effects on Mg/Ca and Sr/Ca ratios in benthic foraminifera : aragonitic species Hoeglundina elegans", Paleoceanography 21 (2006): PA1007, DOI:10.1029/2005PA001158, https://hdl.handle.net/1912/3440
Showing items related by title, author, creator and subject.
Benthic foraminifera living in Gulf of Mexico bathyal and abyssal sediments : community analysis and comparison to metazoan meiofaunal biomass and density Bernhard, Joan M.; Sen Gupta, Barun K.; Baguley, Jeffrey G. (2005-12-07)Benthic foraminiferal biomass, density, and species composition were determined at ten sites in the Gulf of Mexico. During June 2001 and June 2002, sediment samples were collected with a GoMex boxcorer. A 7.5-cm diameter ...
Impact of intentionally injected carbon dioxide hydrate on deep-sea benthic foraminiferal survival Bernhard, Joan M.; Barry, James P.; Buck, Kurt R.; Starczak, Victoria R. (2008-10)Sequestration of carbon dioxide (CO2) in the ocean is being considered as a feasible mechanism to mitigate the alarming rate in its atmospheric rise. Little is known, however, about how the resulting hypercapnia and ocean ...
Taxonomic notes on the abyssal agglutinated benthic foraminifera of the HEBBLE area (lower Nova Scotian Continental Rise) Kaminski, Michael A. (Woods Hole Oceanographic Institution, 1983-09)Eighty species and morphological varieties of agglutinated benthic foraminifera were identified in sediments from the HEBBLE Site (4800 m depth) and the HEBBLE Shallow Site (4185 m) on the lower Nova Scotian Continental ...