Proton pumping accompanies calcification in foraminifera.

Ocean acidification is known to impact marine calcifiers by altering carbonate chemistry. It was already known that inorganic dissolution increases with lower pH. However, the extent to which organisms can regulate their calcification remains unclear. Biomineralization involves complex biochemical pathways. Prior research has shown that calcification is influenced by environmental CO2 levels. But the mechanisms by which marine organisms adapt are not fully understood. This gap motivated a focus on intracellular processes in calcifying organisms. No prior work had resolved how proton dynamics might influence calcification under acidified conditions. Understanding these processes is crucial for predicting marine ecosystem responses.

This study aimed to clarify how calcification occurs in foraminifera under varying CO2 conditions. The specific problem addressed is the role of proton pumping in carbonate formation. Researchers wanted to determine if calcification depends on carbonate ion availability. They also sought to identify the molecular mechanisms involved. The motivation stems from uncertainty about marine calcifier resilience to acidification. By focusing on intracellular pH regulation, the study addresses a key knowledge gap. The goal was to examine whether proton fluxes could maintain calcification under high pCO2. This approach allows for a mechanistic understanding of calcifier adaptation.

The study used a combination of physiological and molecular techniques. Researchers measured intracellular pH changes during calcification. They tracked proton fluxes using fluorescent indicators. V-type H+ ATPase activity was analyzed via Western blotting. Calcification rates were quantified under controlled pCO2 conditions. The experimental setup involved culturing foraminifera in acidified seawater. Proton transport mechanisms were tested using pharmacological inhibitors. The results were compared across a range of CO2 concentrations.

The strongest finding was that calcification occurs via bicarbonate conversion to carbonate in the cytoplasm. Proton pumping was shown to drive this transformation. V-type H+ ATPase was identified as the key proton transporter. Calcification rates remained stable despite elevated pCO2 levels. The process does not rely on carbonate ion availability. Instead, total dissolved CO2 supports calcification. Proton fluxes were maintained across a wide CO2 gradient. These results suggest that calcification is not limited by carbonate ion concentration.

The authors propose that calcification is driven by active proton pumping rather than carbonate ion availability. This mechanism allows foraminifera to maintain calcification under acidified conditions. The study suggests that marine calcifiers may be more resilient than previously thought. V-type H+ ATPase is essential for maintaining proton fluxes. The findings imply that global marine carbonate production could remain stable. The research highlights the importance of intracellular pH regulation. It was already known that calcification is sensitive to environmental changes. This work provides new insights into the biochemical basis of calcifier adaptation.