Global change will likely result in an expansion of open ocean oxygen minimum zones, enhanced atmospheric deposition of nutrients and acidification of the surface ocean on very short, human time-scales. It is imperative that we quantitatively understand the pathways, interactions and environmental regulation of microbial processes that control oceanic nutrient cycling in the water column and sediments. To achieve these objectives a combination of chemical, molecular, microbiological and mathematical modelling techniques are used. NanoSIMS technology enables us to link the identity of microbial cells in a complex microbial community to cellular uptake rates and determine nutrient fluxes.