A mechanistic field investigation of the physiological response of phytoplankton to past fluctuations in surface water carbonate chemistry

The goal of this PhD studentship is to take advantage of the geological record at times of contrasting surface water saturation state (different glacial-interglacial cycles) to probe the mechanistic relationship between the physiological response across different species of these key primary producers for periods when carbonate chemistry of surface waters is known to have changed. By focusing on the more recent times, we have the best constraint on the carbonate chemistry of the ocean system, and can obtain a primary signal of production rather than an overprint of preservation. The aim is to couple established and novel techniques to generate combined records of calcification (coccolithophores only) and photosynthetic efficiency (diatoms and coccolithophores), and assuming that the population structure and size dominates the export of carbon, to chart the size distribution variations of those phytoplankton through time.