Comparison of two potential strategies of planktonic foraminifera for house building: Mg 2+ or H + removal?

Effect of salinity and seawater calcite saturation state on Mg and Sr incorporation in cultured planktonic foraminifera

“…This strategy would not be as costeffective as extracting the same [Mg 2+ ] regardless of the element concentration of the parent solution. This assumption is in line with inorganic calcite precipitation studies by Zeebe and Sanyal (2002) in which it is shown that, in order to initiate the calcification process at biogenic precipitation rates, the best cost-effective strategy is H + removal from the calcifying area. Therefore, the foraminifer would not change the rate at which Mg 2+ is extruded from the cell in order to calcify.…”

“…3A, B and C and 4A). Higher amounts of extracted Mg 2+ -coming from the parent solution into the foraminifer cytoplasm -would mean an increase in the energy required to extrude this excess of Mg 2+ from the cell (Zeebe and Sanyal, 2002). This strategy would not be as costeffective as extracting the same [Mg 2+ ] regardless of the element concentration of the parent solution.…”

Biomineralization in perforate foraminifera

“…Carbon dioxide uptake and proton efflux are also directly related in cyanobacteria (Ogawa and Kaplan, 1987). Ter Kuile et al (1989b) suggested that Ca 2+ is taken up by Ca 2+ -ATPase and this mechanism was subsequently used by Zeebe and Sanyal (2002) and Zeebe et al (2008) to show that H + removal is far more energy-efficient than Mg 2+ -removal during calcification. Such a mechanism would be consistent with a coupling of ion transporters (e.g.…”

“…These conditions are only partly known in benthic species (e.g. Erez, 2003;Bentov and Erez, 2005) and have only been modeled in planktonic species Zeebe and Sanyal, 2002). The volume between the crystal surface and the shielding cytoplasmic envelope or pseudopodial network is extremely small, limiting interpretation from light microscopic observations.…”

“…However, TEM images of initial calcification in O. universa and other planktonic species suggest that the privileged space between rhizopodia and calcifying surfaces may be b 10 nm (Bé et al, 1979;Spero, 1988). Little is known about the chemical composition of the fluid from which CaCO 3 nucleates, but high concentrations of Ca 2+ and CO 3 2 − need to be actively maintained, while the [Mg 2+ ] needs to be reduced to satisfy observations and ensure calcification (Zeebe and Sanyal, 2002). Elevated pH at the site of calcification would promote the conversion of CO 2 and HCO 3 − to CO 3 2− , thereby enhancing CaCO 3 nucleation and growth.…”