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 (N 2 ) 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 N 2 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 N 2 fixation, the global distribution of which is re‐estimated. The new estimate shows a significant increase in N 2 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 N 2 fixation rate.