I then investigated a key component of these assemblages, Subbotina, using individual morphological and geochemical measurements to link their traits to the environment and assess their persistence through the climatic fluctuations of the Middle Eocene (Chapter 3). The results from this study show that analytical size fraction choice is a key determinant of diversity signals in deep-time and furthermore it is small species that maintain ecological function during transient climatic events. I created a diversity record of planktonic foraminifera through the Middle Eocene Climatic Optimum comprising of 22,800 individuals classified to three taxonomic levels and investigated the responses of these assemblages using effective diversity: a novel approach for Palaeogene and deep-time systems (Chapter 2). The primary objective of this thesis is to measure and understand the relationship between planktonic foraminifera and their environment, to enable a more biologically informative assessment of the fossil record. 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. How we utilize the fossil record is therefore of critical Importance. 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. What is unknown is how biotic communities and ecosystems will react to this change on both short and long timescales.
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