Autotrophic Dissolved Organic Phosphorus Uptake Stimulates Nitrogen Fixation in Subtropical Gyres

Abstract Dissolved organic phosphorus (DOP) has been identified as a key phosphorus source that supports primary production and microbial nitrogen (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. Direct DOP assimilation reduces phosphorus limitation in nutrient‐depleted gyres, thereby stimulating global N2 fixation, the global distribution of which is re‐estimated. The new estimate shows a significant increase in N2 fixation rates in the North Atlantic compared to the previous estimate because 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.