Seawater carbonate chemistry and Mg/Ca ratios of laboratory-grown neogloboquadrina foraminifera

• Main Authors: Davis, Catherine V, Fehrenbacher, Jennifer, Hill, Tessa M, Russell, Ann D, Spero, Howard J
• Format: Dataset
• Language: English
• Published: PANGAEA 2017
• Subjects: Alkalinity; total; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bodega_Head; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Description; EXP; Experiment; Foraminifera; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Heterotrophic prokaryotes; Laboratory experiment; Magnesium/Calcium ratio; Neogloboquadrina incompta; Neogloboquadrina pachyderma; North Pacific; OA-ICC; Ocean Acidification International Coordination Centre; Open ocean; Other; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Registration number of species; Salinity; standard deviation; Shell dimension; Single species; Species; Temperate; Temperature; water; Type; Uniform resource locator/link to reference; Bering Sea; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.892335; https://doi.org/10.1594/PANGAEA.892335

Mg/Ca ratio paleothermometry in foraminifera is an important tool for the reconstruction and interpretation of past environments. However, existing Mg/Ca:temperature relationships for planktic species inhabiting mid- and high- latitude environments are limited by a lack of information about the development and impact of low-Mg/Ca ratio “crusts” and the influence of the carbonate system on Mg/Ca ratios in these groups. To address this, we cultured individual specimens of Neogloboquadrina incompta and Neogloboquadrina pachyderma in seawater across a range of temperature (6 °- 12 °C) and pH (7.4 – 8.2). We found by laser ablation inductively couple mass spectrometry analyses of shells that culture-grown crust calcite in N. incompta had a lower Mg/Ca ratio than ontogenetic calcite formed at the same temperature, suggesting that temperature is not responsible for the low Mg/Ca ratio of neogloboquadrinid crusts. The Mg/Ca:temperature relationship for ontogenetic calcite in N. incompta was consistent with the previously published culture-based relationship and no significant relationship was found between Mg/Ca ratios and pH in this species. However, the Mg/Ca ratio in laboratory cultured N. pachyderma was much higher than that reported in previous core-top and sediment trap samples, due to lack of crust formation in culture. Application of our ontogenetic calcite-specific Mg/Ca:temperature relationships to fossil N. pachyderma and N. incompta from five intervals in cores from the Santa Barbara Basin and the Bering Sea show that excluding crust calcite in fossil specimens may improve Mg/Ca-based temperature estimates.