Ammonium was injected from the subseafloor hydrothermal system at the Endeavour Segment, Juan de Fuca Ridge, into the deep-sea water column resulting in an NH4 þ-rich (6177 nM) neutrally buoyant hydrothermal plume. This NH4 was quickly removed by both autotrophic ammonia oxidation and assimilation. The former accounted for at least 93% of total net NH4 þ removal, with its maximum rate in the ne...
