WAITING-OUT THE CRETACEOUS-PALEOGENE MASS EXTINCTION EVENT (Invited Presentation)

Planktonic foraminifera, like calcareous algae, are remarkable recorders of the Cretaceous-Paleogene mass extinction event in spite of severe extinction losses (>90% of species). A recent comparative investigation of calcareous primary producers pointed to two key traits for surviving the impact winter: a resting phase and the ability to consume organic carbon (i.e., mixotrophy). Extinction patterns in foraminifera and other marine clades also suggest that many of the survivors (and early diversifiers) may have waited-out the bad times through some form of metabolic suppression or resting phase, including strategies like diapause or the presence of a large propagul bank. The implications and utility of this approach in the prolonged aftermath of the K-Pg boundary are multifold. Here I leverage the unprecedented clarity provide by recent work on the environmental effects of the Chicxulub impact –including darkness, impact winter, acidification, and (subsequent) productivity changes– to consider the relative importance of each selective filter on the survivorship patterns observed. This context is then used to reconsider the structure and function early Paleocene food-webs in the open ocean.