Paleoecology and evolutionary response of planktonic foraminifera to themid-Pliocene Warm Period and Plio-Pleistocene bipolar ice sheet expansion

The Pliocene-Recent is associated with many important climatic and paleoceanographic changes, which have shaped the biotic and abiotic nature of the modern world. The closure of the Central American Seaway and the development and intensification of Northern Hemisphere ice sheets had profound global impacts on the latitudinal and vertical structure of the oceans, triggering the extinction and radiation of many marine groups. In particular, marine calcifying planktonic foraminifera, which are highly sensitive to water column structure, exhibited a series of extinctions as global temperatures fell. By analyzing high-resolution (similar to 5 kyr) sedimentary records from the Eastern Equatorial Pacific Ocean, complemented with global records from the novel Triton dataset, we document the biotic changes in this microfossil group, within which three species displayed isochronous co-extinction, and species with cold-water affinity increased in dominance as meridional temperature gradients steepened. We suggest that these changes were associated with the terminal stages of the closure of the Central American Seaway, where following the sustained warmth of the mid-Pliocene Warm Period, bipolar ice sheet expansion initiated a world in which cold- and deep-dwelling species became increasingly more successful. Such global-scale paleoecological and macroevolutionary variations between the Pliocene and the modern icehouse climate would suggest significant deviations from pre-industrial baselines within modern and future marine plankton communities as anthropogenic climate forcing continues.

Automated summary

The Pliocene-Recent period has witnessed significant climatic and paleoceanographic changes that have transformed the modern world. The closure of the Central American Seaway and the expansion of Northern Hemisphere ice sheets have globally impacted the structure of oceans, leading to the extinction and radiation of marine species. By examining sedimentary records from the Eastern Equatorial Pacific Ocean and global datasets, researchers have observed extinctions and dominance shifts in marine calcifying planktonic foraminifera, which are sensitive to water column structure and temperature gradients. These changes are associated with the closure of the Central American Seaway and the subsequent expansion of polar ice sheets, favoring cold- and deep-water species. These findings have implications for understanding the impact of anthropogenic climate change on modern marine plankton communities.