Estuaries are vulnerable to anoxia induced by reduced freshwater inflows which is of particular relevance to Australia under conditions of drought and climate change. Anoxia has the potential to both increase and reduce nitrogen (the limiting nutrient in coastal ecosystems) removal efficiency, however, this remains highly uncertain owing to a lack of studies. This project will combine process studies with hydrodynamic biogeochemical modeling to provide insight into how anoxia affects nitrogen cycling and retention in the Yarra Estuary, and the interactions between river flow and nitrogen loading. The new knowledge and approach gained from this project will help set ecological river inflow requirements for estuaries.