THE ECOLOGICAL RESPONSE OF PLANKTON TO MAJOR MESOZOIC AND CENOZOIC CLIMATE EVENTS (Invited Presentation)

Anthropogenic disruptions including climate change, habitat destruction, pollution, overfishing, etc. are causing extreme pressure on the biosphere, which has the potential to cause a major extinction event if we do not take corrective action soon. Earth history contains numerous examples of extinctions caused by severe climatic and environmental changes which can help us contextualize modern change. However, it also contains numerous examples of severe climatic and environmental changes which did not lead to significant extinction, or which only caused extinctions of certain groups. By comparing the biotic response of individual groups of organisms during different paleoceanographic events we can build an understanding of what types of changes affected the diversity of those groups in the past, and thus which groups might be at risk from changes occurring today. Here, we examine the species-level diversity of planktic foraminifera and calcareous nannoplankton from the Mesozoic to the present across a number of major events, including the Triassic-Jurassic boundary (T-J), Cretaceous Oceanic Anoxic Events (OAEs), the Cretaceous-Paleogene (K-Pg) mass extinction, the Paleocene-Eocene Thermal Maximum (PETM) and the Eocene-Oligocene Transition (EOT). We find that, with the exception of the T-J and the K-Pg, plankton extinction is decoupled from the overall marine extinction. Extinction in the plankton appears to be primarily caused by changes in water column stratification, upper water column temperature, and perhaps, chemistry. Changes which cause extinction in other marine groups, like anoxia and acidification, have little effect on the plankton or are associated with speciation.