Seminar: Dr. Alison Taylor, UNC-Wilmington

Cell Biology of Coccolithophores: Insights into Calcification, Physiology, and Ecology (Host: Adrian Marchetti) Understanding the cell biology and mechanism of calcification in coccolithophores, the most significant producers of marine biogenic calcite, is of central importance if we are to fully understand their roles in biogeochemical cycles, predict responses to climate change, and validate paleoproxies. We are therefore investigating the cell structures and transport processes that mediate the intracellular production of the CaCO₃ plates known as coccoliths, which are secreted onto the cell surface to produce the extracellular covering known as the coccosphere. Of particular interest is how coccolithophores maintain homeostatic balance, such as pH, under a wide range in external conditions and internal metabolic states, and their physiological responses to changing surface ocean pH. More recently, we have demonstrated the presence of diatom-like silicon transporters and a requirement for Si in calcification in some, but not all groups of coccolithophores. This has important implications for their competitive interactions under Si-limited conditions. Several examples of how we are using biophysics, molecular biology and high-resolution imaging to address these questions will be discussed.