Antarctic sea ice algae : primary production and carbon allocation

Sea ice is a semi-solid matrix of brine-filled channels, typically displaying strong vertical gradients in temperature, salinity, light, and space. Prolonged biological activity within the confines of the brine channels itself alters the microenvironment and physicochemistry. To be able to cope with these changes, ice algae display a complex suite of physiological and metabolic adaptations. One such adaptation is the exudation of photosynthetically-derived organic carbon. Research undertaken for the thesis details primary production and carbon allocation of ice algal communities in laboratory and field conditions, and discusses the relationships between microbial growth dynamics, responses to physicochemical change, and ecosystem dynamics. The thesis finds that sea ice algae are capable of exuding large quantities of photosynthetically-derived organic carbon. Allocation to exuded organic carbon is highest during times of adverse conditions, such as challenging biochemical and physicochemical conditions. The composition of exuded carbon varies between defined pools, including dissolved organic carbon, colloidal organic carbon, and extracellular polymeric substances. The observed magnitude of changes in carbon allocation indicates that each extracellular carbon pool imparts different ecological roles and/or benefits to the producer organism. The thesis highlights the complexity of sea ice primary productivity, subsequent carbon allocation, and the driving factors within the diverse sea ice habitat. With an increased ability to quantify direct exudation of organic carbon, the contribution of sea ice algae to total primary production and carbon flux dynamics across ice-covered seas could now be estimated.