Temperature Influence on Proton Pumping and Mg-Incorporation in Foraminifera

The Mg/Ca ratio in foraminiferal shells is commonly used as a proxy for reconstructing sea surface and bottom water temperatures. However, its incorporation results from complex interactions between seawater conditions and biologically regulated factors. While the former effects are well-constrained, poorly understood biological factors contribute to interspecies variations in Mg/Ca-temperature calibrations and a notable difference in Mg sensitivity compared to inorganically precipitated calcium carbonates. Here we show that temperature significantly influences cellular ion modulation in low-Mg species, leading to elevated enzymatic reaction rates that enhance H⁺ removal (J = 0.67 to 5.00 nmol^-s) during calcification, and boost the precipitation rate. On high-Mg species, on the other hand, a similar fivefold increase in H⁺ local flux was observed (J = 0.08 to 0.40 nmol^-s), but its impact on the calcification rate was mild. In both cases, H⁺ pumping rates align with Mg uptake, indicating a potential (indirect) link between temperature-sensitive behavior of transporters and Mg partitioning.