[2017 GO-SHIP P06 transect TDN d15N] - Total dissolved nitrogen (TDN) concentrations and δ15N measurements from samples collected on R/V Nathaniel B. Palmer GO-SHIP cruises NBP1706 and NBP1707 in the South Pacific from Jul 3 to Sep 30, 2017 (Collaborative Research: Dissolved organic phosphorus controls on marine nitrogen fixation and export production)

Samples were collected roughly every 2 degrees of longitude across the transect. Samples were measured using persulfate oxidation of the TDN in the sample to nitrate, and then using the denitrifier method to measure the d15N of the resulting nitrate.

Dissolved organic nitrogen (DON) is the dominant form of bioavailable nitrogen in the euphotic zone of subtropical gyres, where nitrate (NO3-) concentrations are low. However, identifying regions where DON consumption may support surface ocean productivity remains challenging due to the relatively narrow range in euphotic zone DON concentrations. These paired measurements of TDN concentrations and their d15N values will help resolve patterns of DON production and consumption across the largest subtropical ocean gyre.