Seawater carbonate chemistry and biological processes of foraminifera, Globigerinoides ruber and Globigerinella siphonifera during experiments, 2011

• Main Authors: Kisakürek, B, Eisenhauer, Anton, Böhm, Florian, Hathorne, Ed C, Erez, Jonathan
• Format: Dataset
• Language: English
• Published: PANGAEA 2011
• Subjects: Alkalinity; total; standard deviation; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Finnigan TRITON thermal ionization mass spectrometer (TIMS); Foraminifera; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Globigerinella siphonifera; shell; weight; Globigerinoides ruber; Growth/Morphology; Growth rate; Heterotrophic prokaryotes; Identification; Laboratory experiment; Measured; OA-ICC; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.763297; https://doi.org/10.1594/PANGAEA.763297

Specimens of two species of planktic foraminifera, Globigerinoides ruber and Globigerinella siphonifera, were grown under controlled laboratory conditions at a range of temperatures (18-31 °C), salinities (32-44 psu) and pH levels (7.9-8.4). The shells were examined for their calcium isotope compositions (d44/40Ca) and strontium to calcium ratios (Sr/Ca) using Thermal Ionization Mass Spectrometry and Inductively Coupled Plasma Mass Spectrometry. Although the total variation in d44/40Ca (~0.3 per mill) in the studied species is on the same order as the external reproducibility, the data set reveals some apparent trends that are controlled by more than one environmental parameter. There is a well-defined inverse linear relationship between d44/40Ca and Sr/Ca in all experiments, suggesting similar controls on these proxies in foraminiferal calcite independent of species. Analogous to recent results from inorganically precipitated calcite, we suggest that Ca isotope fractionation and Sr partitioning in planktic foraminifera are mainly controlled by precipitation kinetics. This postulation provides us with a unique tool to calculate precipitation rates and draws support from the observation that Sr/Ca ratios are positively correlated with average growth rates. At 25 °C water temperature, precipitation rates in G. siphonifera and G. ruber are calculated to be on the order of 2000 and 3000 µmol/m**2/h, respectively. The lower d44/40Ca observed at 29 °C in both species is consistent with increased precipitation rates at high water temperatures. Salinity response of d44/40Ca (and Sr/Ca) in G. siphonifera implies that this species has the highest precipitation rates at the salinity of its natural habitat, whereas increasing salinities appear to trigger higher precipitation rates in G. ruber. Isotope effects that cannot be explained by precipitation rate in planktic foraminifera can be explained by a biological control, related to a vacuolar pathway for supply of ions during biomineralization and a pH regulation mechanism ...