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Marine sediments hold a vast story of changing climatic and oceanographic conditions in Earth's geologic past. This story is largely written by unicellular organisms: notably algae, zooplankton, and archaea. These organisms are abundant and widespread and, crucially, their calcitic shells or certain components of their biomass are resistant to degradation and can be preserved for millions of years. Paleoceanographers study these remains and have found that the chemical makeup of calcite and of certain biomarkers, or molecular fossils, is dependent on the seawater temperature in which they grow. As a result, proxies for temperature have been identified based on ratios of chemical components found in marine sediments. Although these proxies are robustly validated in modern marine settings they are not perfect paleo-thermometers. Instead, each proxy can be subject to a number of confounding factors related to seawater chemistry, ecology, physiology, and mixing effects.

This thesis aims to provide additional mechanistic understanding of both thermal and non-thermal influences on several marine temperature proxies. The thesis provides insight into biases in several ocean proxies in the Mediterranean Sea.