Long‐Term Reorganization of Ocean Nutrient Distribution

Abstract Nutrient availability is a major driver of ocean biodiversity and productivity, yet long‐term global changes remain poorly constrained. Using over 14 million nitrate and phosphate measurements collected between 1925 and 2025, we quantify long‐term trends in nutrient concentrations across ocean biomes and depths. We find that surface waters in oligotrophic and mesotrophic regions show significant declines in phosphate, whereas nitrate is also slightly decreasing in oligotrophic but increasing in mesotrophic regions. Many coastal areas exhibit nutrient enrichment. Subsurface waters reveal widespread nitrate accumulation, suggesting an imbalance driven by biological nitrogen fixation and reduced vertical mixing. Comparison with Earth system models indicates that current simulations underestimate the pace of nutrient shifts. Our results highlight a large‐scale biogeochemical reorganization of ocean nutrient distributions that may intensify under future climate warming.