Seven years of time-series observations of biogeochemical processes in the subtropical North Pacific Ocean gyre have revealed dramatic changes in the microbial community structure and in the mechanisms of nutrient cycling in response to large-scale ocean-atmosphere interactions. Several independent lines of evidence show that the fixation of atmospheric nitrogen by cyanobacteria can fuel up to half of the new production. These and other observations demand a reassessment of present views of nutrient and carbon cycling in one of the Earth’s largest biomes.