Copyright © 2018 by the International Society of Offshore and Polar Engineers (ISOPE) Vertical profiles of seawater neodymium (Nd) concentration and isotopic composition were determined for a location near the Takuyo-Daigo Seamount in the northwest Pacific Ocean. The Nd isotopic composition profile is similar to the surface layer Nd isotopic composition of ferromanganese crusts collected from the Takuyo-Daigo Seamount. This confirms that Nd in the surface layer of ferromanganese crusts is supplied directly by ambient seawater.