The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Dissolved organic phosphorus (DOP) has been identified as a key phosphorus source that supports primary production and microbial N₂ fixation. However, the specific contribution and spatial distribution of DOP utilization remain poorly understood due to limited in-situ measurements. In this study, we explored the role of DOP in supporting N₂ fixation using a modified inverse biogeochemical ocean model. Our findings reveal that DOP utilization primarily occurs in subtropical gyres, where it serves as a critical phosphorus source. The direct DOP assimilation reduces phosphorus limitation in nutrient-depleted gyres, thereby stimulating global N₂ fixation, whose global distribution is re-estimated. The new estimate shows a significant increase in N₂ fixation rates in the North Atlantic compared to the previous estimate due to the fact that DOP utilization reduces the severe phosphorus limitation in that region. Neglecting DOP utilization would result in an approximately 9% underestimation of the global N₂ fixation rate.

dissolved organic phosphorus, nitrogen fixation, inverse model