Primary production in the ocean is critically important for human wellbeing—it regulates atmospheric carbon dioxide as well as sustaining almost all ocean life. But models predicting the impacts of climate change do not agree on the sign of ocean primary production in the coming century. Currently, satellite observations tell us how ocean primary productivity is changing, but not the underlying controls. Fieldwork and modelling show nutrient limitation is key, but there is currently no way to observe nutrient limitation at the scales needed to monitor climate change impacts or benchmark the accuracy of models. This project aims to overcome the scaling problem using direct, nutrient-regulated fluorescence signals passively emitted from phytoplankton and detected by satellite sensors in space.
In the Ocean Glow project, we are taking a two-pronged approach to try to break through the current blockage in our understanding of satellite-detected fluorescence signals. In the first prong, a novel laboratory mesocosm facility has been constructed and is being used to quantify the key factors regulating phytoplankton fluorescence emission, in the same way that it is stimulated and detected by satellites. In the second prong we are connecting these experimental results with the real world by undertaking field observations on research cruises through the global ocean. In the final stage of the project we plan to use this ground-based assessment to perform a data-informed deconvolution of the satellite fluorescence signal to observe nutrient limitation at a global, time-resolved scale using the existing, two-decade satellite record. If we are successful in this, it will deliver the tool needed to make important mechanistic assessments of how climate change is impacting ocean productivity.
