The fossil record of larger symbiont-bearing foraminifera: A unique archive to assess the impact of decreasing pH and calcite saturation

Over the past two centuries, fossil fuel burning and other anthropogenic activities have caused the atmospheric CO₂ concentration to rise from 280 ppm to 419 ppm. Over the same time interval, the surface oceans have absorbed more than 500 billion tons of carbon dioxide from the atmosphere, or approximately 30 % of the total anthropogenic carbon dioxide emissions. This absorption of CO₂ from the atmosphere has benefitted human mankind significantly by reducing the greenhouse gas levels in the atmosphere. When anthropogenic CO₂ is absorbed by seawater, chemical reactions occur that reduce seawater pH, concentrations of carbonate ions, and the saturation states of the biominerals aragonite and calcite in a process commonly referred to as ocean acidification. When the pH and carbonate saturation drop in seawater, carbonate biominerals in shells and skeletons may begin to dissolve, and the water become corrosive for this reason.

Atmospheric CO₂, pH and carbonate saturation have fluctuated significantly over the Phanerozoic history in the oceans. This research presentation focuses on the on the abundance, biodiversity and biogeography of larger benthic symbiont-bearing foraminifera during the Phanerozoic. Benthic and planktic foraminifera produce approximately 20 % of the overall carbonate in modern oceans and as such they are major components of the carbonate budget. How did larger benthic foraminifera react to changes in the oceans over the course of the Phanerozoic history? How did high CO₂ and low pH levels impact this important group and what lesson can we learn from the fossil record for future developments?

This presentation illustrates the reaction of modern and fossil larger benthic symbiont-bearing foraminifera (LBF) to major perturbations in the ocean systems. Larger symbiont-bearing foraminifera have an excellent fossil record, are ubiquitous components of tropical and subtropical biotas and contribute significantly to the carbonate produced in the tropical world's oceans. The fossil record of larger symbiont-bearing foraminifera provides a unique archive to assess the impact of decreasing pH and calcite saturation on environments in future oceans.