Award: OCE-1220554

This project studied ocean acidification across the Paleocene-Eocene Thermal Maximum, a natural acidification event that happened ~56 million years ago, and which bears similarities to modern ocean acidification. Using boron isotopes in the fossil shells of marine plankton, we established that the ocean acidified by ~0.3 units at the PETM, an extent similar to what is expected by the end of this century, but over a much longer period of time (~4 thousand years compared to 200 years). Despite the longer duration of the onset of acidification at the PETM, ocean ecosystems experienced dwarfism, extinction, and shifts in community composition. This coincidence of acidification and ecosystem changes highlights the likely negative impacts of unabated CO2 emissions and associated ocean acidification on modern ecosystems in the coming decades and centuries. While ecosystems did not entirely collapse at the PETM, mankind will have to anticipate future ecosystem changes, which may include species that are consumed by humans; e.g., oyster growth is already impacted by ongoing acidification. In addition to the ecosystem changes associated with the onset of the PETM, our records also demonstrate that it took Earth tens of thousands of years to recover from this perturbation. For humans this means that the path we are embarking on today will not only be felt by our children and grandchildren, but by hundreds of generations to come. Training young scientists and public outreach: This project allowed the training of two graduate students and one postdoc, who have been guided to design the sampling and interpret data from individual study sites. In addition, results from this study have been incorporated into college and graduate level courses at Columbia University (V1030 Introduction to Oceanography, W4920 Paleoceanography, W4926 Chemical Oceanography), the Urbino Summer School in Paleoclimatology, public lectures at the Lamont-Doherty Earth Observatory, at the AARP Rockland in Nyack, the Laguardia High School in NYC, and on a University alumni cruise to Costa Rica. Last Modified: 09/14/2016 Submitted by: Baerbel Hoenisch