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Speaker: Lorna Kearns, Postdoctoral Fellow, University of Texas Institute of Geophysics

Host: Chris Lowery

Title: Descent into the icehouse: how overlooked species of planktonic foraminifera maintained community structure through the middle Eocene

Abstract: Humans are changing the Earth. What is unknown is how biotic communities and ecosystems will react to these changes on both short and long timescales. The fossil record can provide us with a means of investigating ecosystem responses to long-term climatic fluctuations which can act as baselines for future anthropogenic induced change. How we utilize the fossil record is therefore of critical importance. The high spatial and temporal resolution of the planktonic foraminifera fossil record provides an ideal system to investigate ecosystem responses to climatic fluctuations at multiple scales and levels. Here I will demonstrate that by using appropriate methods the relationship between planktonic foraminifera and their environment can be used to facilitate a more biologically informed assessment of the fossil record.

I will present a diversity record of planktonic foraminifera through the Middle Eocene Climatic Optimum comprising of 22,800 individuals which shows analytical size fraction choice is a key determinant of diversity signals in deep-time. Furthermore, this record shows that it is small species that maintain ecological function during transient climatic events. Through coupled trait and geochemical analysis, I will then show that survival of one planktic foraminifera genus, Subbotina, through this climatically dynamic interval was aided by trait plasticity and a wider ecological niche than previously thought for a subthermocline dwelling genus supporting a generalist life strategy.

These results raise fundamental questions about how communities respond to climate excursions. In addition, our results emphasize the need to design studies with the aim of collecting the most inclusive data possible to allow detection of community changes and determine which species are likely to dominate future environments.