The paper introduces a new quasi-conservative tracer, \( N^* \), defined as a linear combination of nitrate and phosphate, to investigate the distribution of nitrogen fixation and denitrification in the world oceans. The spatial patterns of \( N^* \) are determined using data from the Geochemical Ocean Sections Study (GEOSECS) cruises (1972-1978) and additional cruises in the Atlantic Ocean. Low \( N^* \) concentrations (< -3 μmol kg^-1) are found in the Arabian Sea and eastern tropical North and South Pacific, consistent with direct observations of water column denitrification in these oxygen minimum zones. High \( N^* \) concentrations (> 2.0 μmol kg^-1) indicative of prevailing nitrogen fixation are observed in the thermocline of the tropical and subtropical North Atlantic and the Mediterranean, suggesting that these basins act as sources of fixed nitrogen. The study estimates a nitrogen fixation rate of 28 Tg N yr^-1 in the North Atlantic Ocean, which is about 3 times larger than the most recent global estimate. The results suggest that the present-day budget of nitrogen in the ocean may be in approximate balance. The concept of \( N^* \) is based on the assumption of a constant stoichiometric ratio during nitrification, and it effectively eliminates the effect of nitrification on nitrate and phosphate concentrations. The distribution of \( N^* \) is consistent with known spatial patterns of denitrification and nitrogen fixation, supporting the utility of this tracer for global-scale investigations.The paper introduces a new quasi-conservative tracer, \( N^* \), defined as a linear combination of nitrate and phosphate, to investigate the distribution of nitrogen fixation and denitrification in the world oceans. The spatial patterns of \( N^* \) are determined using data from the Geochemical Ocean Sections Study (GEOSECS) cruises (1972-1978) and additional cruises in the Atlantic Ocean. Low \( N^* \) concentrations (< -3 μmol kg^-1) are found in the Arabian Sea and eastern tropical North and South Pacific, consistent with direct observations of water column denitrification in these oxygen minimum zones. High \( N^* \) concentrations (> 2.0 μmol kg^-1) indicative of prevailing nitrogen fixation are observed in the thermocline of the tropical and subtropical North Atlantic and the Mediterranean, suggesting that these basins act as sources of fixed nitrogen. The study estimates a nitrogen fixation rate of 28 Tg N yr^-1 in the North Atlantic Ocean, which is about 3 times larger than the most recent global estimate. The results suggest that the present-day budget of nitrogen in the ocean may be in approximate balance. The concept of \( N^* \) is based on the assumption of a constant stoichiometric ratio during nitrification, and it effectively eliminates the effect of nitrification on nitrate and phosphate concentrations. The distribution of \( N^* \) is consistent with known spatial patterns of denitrification and nitrogen fixation, supporting the utility of this tracer for global-scale investigations.