Stoichiometric, Isotopic, and Modeling Tracers of Marine Autotrophic Dissolved Organic Nutrient Production and Consumption

Dissolved organic N (DON) and dissolved organic P (DOP) represent the largest pools of bioavailable N and P in oligotrophic surface waters. While both serve as assimilative nutrient sources for autotrophs when inorganic forms of N and P are scarce, the location and quantitative significance of their utilization remain unclear. Here, we review new geochemical metrics and modeling tools that link surface-ocean DON and DOP to basin-scale biogeochemical processes and identify their source and sink regions. We find that surface-ocean dissolved organic nutrients are influenced by both phosphate and iron stress, as well as denitrification in the Pacific and atmospheric dust deposition in the Atlantic, and support up to 66% and 80% of annual net community production in the western North Pacific and North Atlantic gyres, respectively. Collectively, this work refines our understanding of the role of organic nutrients in supporting the biological pump and the controls on upper-ocean nutrient cycling.