FORAMINIFERA POPULATION DYNAMICS IN THE SOUTHERN HEMISPHERE DURING THE EOCENE HOTHOUSE

Ancient sediments and historical geology can be used to contextualize the effect of modern global warming on biogeochemical cycles in the Earth’s oceans. The Eocene hothouse was a period of extended global warmth that lasted from 56-47 million years ago. Deep-sea sediments were collected from an International Ocean Discovery Program (IODP) Expedition 378 on the Campbell Plateau to for example investigate the impact of global warming on sensitive high-latitude ocean systems during the Eocene. Foraminifera are ubiquitous single-celled calcifying organisms that can be used to reconstruct ancient oceans by studying their population dynamics and isotopic signatures. Preliminary data of planktonic foraminifera population assemblages shows switches in abundance in the genera Morozovella and Acarinina over time. These switches correlate with bulk carbon isotope excursions, supporting the theory that ecosystems in the Southern Ocean changed in response to warming. Despite occupying the same niches in their environment, these genera had very different responses to global change indicating possible key differences in their biology to lead to a divergence in success. Studying how different ancient calcifying organisms respond to a regional change over time can provide valuable information on how modern calcifying organisms will react in a modern warming world.