The Paleocene Eocene Thermal Maximum (PETM), ~56 million years ago, is perhaps the most widely studied global warming event of the Cenozoic era and recently has also become a focus for investigations of past ocean acidification. Carbon cycle perturbation across this event is manifest in records of bottom water ocean acidification but the key to utilizing the PETM in understanding ongoing anthropogenic ocean acidification is to constrain concomitant surface water chemistry change. Currently, data from modelling suggests that levels of carbonate chemistry change in surface waters may have been relatively low and the biotic response of calcifiers is in line with this conclusion. In particular, we see no evidence for a significant carbonate chemistry impact on the production, distribution or micro-evolution of calcifying nannoplankton. Here I discuss the PETM and other pertinent time intervals, including the Mesozoic Oceanic Anoxic Events, considering hypotheses being put forward that include malformation of calcifying plankton and reductions in carbonate accumulation as possible indicators of surface water acidity.
Gibbs, S., 2010. Is there evidence for a biotic response to surface water acidification in the geologic past? American Geophysical Union, Fall Meeting 2010, abstract #PP21E-05. Abstract.
