Calcification in foraminifera largely supported by ion channels- biomineralization pathways and their effect on trace elemental composition

Despite much excellent work in the field of paleoclimatology aiming at the establishment of new proxies, the base of all proxy- environment relationships, the biomineralisation pathway, is currently not adequately known. Yet without understanding the calcification in foraminifera on a cellular level, we are not able to improve existing proxies/ develop new ones and are therefor potentially left with an inadequate reconstruction of e.g. paleo pCO₂ in climate change research. The here presented study remedies this gap by examining the biomineralisation pathway of foraminifera on a cellular level. Two benthic foraminifera (one with symbionts, one without) were cultured under a range of pharmacological inhibitors, targeting calcification relevant ion channels. Both species were found to be highly sensitive to a calcium channel blocker, clearly demonstrating that the majority of calcium ions needed during calcification is taken up via trans-membrane transport in both species. In a similar fashion we could demonstrate that H⁺ ions are pumped out during calcification in the non symbiontic species whereas the symbiontic species was insensitive to the used proton pump inhibitor, which we link to the activity of symbionts. Based on these results an updated biomineralization model will be presented. Additionally trace elemental composition of the cultured foraminifera will be discussed in the light of this biomineralization model, focusing on climate change research relevant proxies.