Effects of temperature on Mg/Ca in neogloboquadrinid shells determined by live culturing

Abstract

[1] New culturing protocols allowed the development of a Mg/Ca temperature calibration equation for Neogloboquadrina pachyderma (d.). When cultured between 9°C and 19.2°C, Mg/Ca in N. pachyderma (d.) shell calcite exhibits a clear dependence on temperature. Shell calcite Mg/Ca increased exponentially with temperature: Mg/Ca = 0.51 À0.15 +0.23 * exp (0.10±0.02*T) . Limited data suggest N. dutertrei exhibit similar elemental temperature relationships to N. pachyderma (d.). We applied the temperature relationship established by culturing to Mg/Ca in neogloboquadrinid shells collected using plankton tows. Compared to measured SST, the calculated temperatures were within ±2°C for Mg/Ca (95% CI). Multiple samples from single tows generally had calculated temperatures that ranged from near-surface values to temperatures consistent with calcification depths down to $70 m. Our work indicates that Mg/Ca temperature calibration equations for temperate and polar foraminiferal species have a similar exponential constant but a higher pre-exponential constant than those for surface-dwelling tropical species. Therefore accurate paleotemperature reconstructions from temperate and polar species require the use of an equation distinct from those used for tropical species.

Reconstructing seawater δ18O from paired coral δ18O and Sr/Ca ratios: Methods, error analysis and problems, with examples from Tahiti (French Polynesia) and Timor (Indonesia)

“…SODA SST regression (b 1 = À0.063 mmol/mol/°C). Published regression slopes of d 18 O vs. SST in biological carbonates range from À0.15&/°C to À0.23&/°C (O'Neil et al, 1969;Bemis et al, 1998;von Langen et al, 2000;Spero et al, 2003). Corals show more or less the same range of d 18 O-SST relationships (À0.15&/°C to À0.22&/°C; Weber and Woodhead, 1972;Wellington et al, 1996;Gagan et al, 1998;Juillet-Leclerc and Schmidt, 2001;Suzuki et al, 2005).…”

Planktic Foraminifera

“…For example, magnesium (Mg) in foraminiferal shells has a close relationship with the water temperature at the time and location of shell formation (Savin and Douglas 1973;Cronblad and Malmgren 1981;Nürnberg 1995;Nürnberg et al 1996). The relationship between water temperature and Mg/Ca has been confirmed not only for living species under natural conditions but also under laboratory conditions (e.g., Delaney et al 1985;Anand et al 2003;von Langen et al 2005). The residence time of Mg in the ocean is about 10 million years and its distribution is heterogeneous (Broecker and Peng 1982).…”

Deglacial ocean warming and marine margin retreat of the Cordilleran Ice Sheet in the North Pacific Ocean

“…Mg/Ca = 0.52 * e (0.10 * Temperature) (±0.7 • C standard error) (1) Other published calibration equations (Mashiotta et al, 1999;von Langen et al, 2005;Nürnberg, 1995;Kozdon et al, 2009) based on temperate and subpolar planktonic foraminiferal species have a similar exponential constant to the Elderfield and Ganssen (2000) calibration, therefore the choice of another calibration equation does not result in a significant difference in reconstructed temperature (Fig. S3).…”