Nitrogen isotope ratio in dissolved organic nitrogen in the subtropical South and North Pacific.

Abstract

In this study, we focused on the relationship between DON and NO₃- in the subtropical South and North Pacific and attempted to quantitatively compare d¹⁵N between DON and NO₃-. The results showed that DON concentrations from the surface to 150 m depth in the subtropical North Pacific were 4 to 5 uM at most points. The d¹⁵N of DON were +0 to +6 which were relatively lower than those of NO₃-. Whereas the DON concentrations from the surface to 100 m depth in the subtropical South Pacific were similar to those in the North Pacific subtropical region, the d¹⁵N of NO₃- up to 200 m depth was +5 ~ +11, and that of DON at the same depth was +5 ~ +9, both higher than in the North Pacific subtropical region.