Emma’s PhD is focused on remotely sensed and in situ observations of fluorescence quantum yield (FQY) in the Southern Ocean. Fluorescence quantum yield is the ratio of photons emitted to those absorbed, serving as a measure of the photosynthetic efficiency of a phytoplankton population. This important biological parameter is influenced by numerous factors including taxonomy, light environment and nutrient status. Understanding the variability in signal through strategic in situ sampling will ultimately allow her to apply her findings to remotely sensed ocean colour data. In order to study FQY from space she will be using a fluorescence line height (FLH) product together with phytoplankton specific absorption determined using an inherent optical properties (IOP) inversion algorithm. She will attempt to attribute variation in the FQY signal to factors identified from her in situ studies. These relationships can be further investigated using the underlying IOP model, which can accommodate various characteristics of phytoplankton communities such as cell size and accessory pigment composition. Having an accurate understanding of the variables affecting FQY will allow her to confidently apply an FQY algorithm over a decadal time series, helping to characterise and better understand Southern Ocean phytoplankton dynamics.