Abrupt and Sustained Acidification in Southern Tethyan Margin During the Paleocene–Eocene Thermal Maximum: Impacts on Foraminifera

Today, many marine organisms are highly sensitive to environmental and climatic changes. The PCO₂/reduced pH scenario is widely considered as the ultimate threat to modern biodiversity. Recently, the increase of PCO₂ and ocean acidification have been significantly reducing the growth and fertilization rates of animals, as well as their reproduction capacity, which raises the question of how marine systems of the Paleocene–Eocene Thermal Maximum (PETM) reacted to the rapid release of several thousand gigatons of isotopically light carbon into the oceans and the atmosphere. The answer to this question may help to investigate the fate of modern and future marine ecosystems in times of sharply rising acidification and CO₂ levels. During the PETM, the marine sediments of the Roman Bridge section (Central Tunisia, southern Tethyan margin) experienced abrupt and sustained acidification advocated by the sharp decrease of Ca concentrations, the near absence of calcite, and the very bad preservation state of foraminifera. The carbonate chemistry changes had significantly influenced the calcifiers. Consequently, the foraminifera population, being sensitive to abrupt acidification, exhibited disruptions during the PETM, including the extinction of species, dwarfism, decrease in abundance and diversity and occurrence of dissolved and fragmented shells.