The Kuroshio Extension is the eastern arm of the Kuroshio western boundary current characterized by a strong latitudinal density front, high levels of eddy kinetic energy, and high chlorophyll. New research is starting to show that the Kuroshio Extension acts as a nutrient stream, leading to enhanced vertical nutrient supply in the frontal region. The combination of these factors suggests that the Kuroshio Extension should act as a hotspot of enhanced productivity. However obtaining direct in situ estimates of productivity over synoptic scales is challenging. In this talk, I present new estimates of net community production (NCP) for the Kuroshio Extension region derived from underway O2/Ar measurements made in spring, summer and early autumn. These gas measurements are made continuously while the vessel is underway, and so provide a synoptic view of local variations in NCP, which should resolve mesoscale (and submesoscale) variability. I explore the relationship between NCP and sea level anomaly and chlorophyll (CHL). There are striking regional and seasonal differences in the degree of coupling between NCP and CHL, with the two almost completely decoupled in the Kuroshio Extension in spring. I explore the mechanistic underpinnings of the relationship between NCP and CHL, and suggest that the Kuroshio Extension nutrient stream might be a key factor in supporting an NCP hotspot decoupled from CHL at the front.