PhD: Identifying critical temperature thresholds in marine ecosystems

Anthropogenic climate change is impacting biodiversity with direct consequences for ecosystem functioning and Earth system dynamics. However, our ability to predict changes is largely limited by the lack of clarity in the complex relationship between environmental and community change. This is particularly true of planktic foraminifera, a major group of calcifying marine plankton and key players in global carbon cycling. Fortunately, planktic foraminifera have an exceptional fossil record that spans multiple short-lived (~100-170 kyrs) global warming events or ‘hyperthermals’ that occurred between ~57-48 Myrs ago, our best geological analogues for the ongoing anthropogenic change. The fossil record across these events provide a unique and direct window into how foraminifera responded to multiple synergistic drivers, accounting for species/trophic level interactions and adaptation, difficult or impossible to observe in laboratory cultures or ecological models. However, how planktic foraminiferal ecosystems change and scale with key environmental parameters such as temperature across hyperthermal events is not well known. Here, we will generate high-resolution records of planktic foraminiferal community and temperature (a “master” climate variable and important driver of planktic foraminiferal diversity) from the same samples across the early Paleogene, an interval characterized by different rates and magnitudes of temperature and associated environmental change. This will allow identification for the first time of critical temperature thresholds for planktic foraminiferal community changes, as well as any characteristic (and therefore) predictable biotic responses, filling key gaps in our understanding of both past and modern ecosystem evolution.

Project research objectives are:

[1] What is the timing and amplitude of sea surface temperatures (SST) change across early Paleogene background (i.e., between events) and “hyperthermal” events?

[2] How do planktic foraminiferal communities change across the early Paleogene background and “hyperthermal” events?

[3]: What are the SST thresholds for inducing different types (e.g., richness, origination, extinction, ecology) of planktic foraminiferal community change and are they the same everywhere in the ocean?

[4] How do SST thresholds compare between different time intervals and thus, what can they tell us about modern and future communities.