Renewal of planktonic foraminifera diversity after the Cretaceous Paleogene mass extinction by benthic colonizers

Planktonic foraminifera are key to understanding paleoclimate and plankton evolution, but their origins are unclear. Here, the authors use a molecular clock to suggest that benthic foraminifera dispersed in plankton and renew planktonic foraminifera diversity after the Cretaceous Paleogene mass extinction. The biotic crisis following the end-Cretaceous asteroid impact resulted in a dramatic renewal of pelagic biodiversity. Considering the severe and immediate effect of the asteroid impact on the pelagic environment, it is remarkable that some of the most affected pelagic groups, like the planktonic foraminifera, survived at all. Here we queried a surface ocean metabarcoding dataset to show that calcareous benthic foraminifera of the clade Globothalamea are able to disperse actively in the plankton, and we show using molecular clock phylogeny that the modern planktonic clades originated from different benthic ancestors that colonized the plankton after the end-Cretaceous crisis. We conclude that the diversity of planktonic foraminifera has been the result of a constant leakage of benthic foraminifera diversity into the plankton, continuously refueling the planktonic niche, and challenge the classical interpretation of the fossil record that suggests that Mesozoic planktonic foraminifera gave rise to the modern communities.

Automated summary

Planktonic foraminifera are important for understanding ancient climate and the evolution of plankton. The origins of these organisms are unclear, but a molecular clock suggests that benthic foraminifera dispersed in the plankton and renewed the diversity of planktonic foraminifera after a mass extinction event. This study shows that calcareous benthic foraminifera are able to actively disperse in the plankton and that modern planktonic clades originated from different benthic ancestors. These findings challenge the classical interpretation of the fossil record and suggest that the diversity of planktonic foraminifera is continuously fueled by benthic foraminifera.