The stoichiometric ratios of particulate carbon (C), nitrogen (N), and phosphorus (P) are critical for assessing biological pump efficiency, yet the vertical evolution of C:N:P ratios within the twilight zone and its regional variability remain poorly constrained. This study utilized observational data from three cruises—GEOTRACES GP09 (oligotrophic North Pacific subtropical gyre), GP16 (eastern tropical Pacific upwelling region), and EXPORTS (subarctic northeast Pacific high‑nutrient, low‑chlorophyll region)—to systematically analyze the vertical distributions of particulate C, N, and P concentrations and their stoichiometric ratios in the upper 500 m. Results show that particulate C:N and C:P ratios increased with depth in all cruises, confirming preferential remineralization of N and P relative to C within the twilight zone. However, the rates of increase differed markedly among regions: the steepest rise in C:P ratio occurred in GP09 (slope = 0.36), followed by GP16 (slope = 0.12), and the most gradual change in EXPORTS (slope = 0.044), indicating that preferential P remineralization is more intense in oligotrophic waters. Correlation analyses revealed that the coupling between elemental ratios and hydrochemical parameters was tighter in more nutrient‑depleted regions, suggesting that the regulatory strength of environmental factors on vertical stoichiometric changes is closely linked to surface nutrient supply. Martin curve fitting further demonstrated that the attenuation coefficients (b‑values) for particulate P in the low‑latitude regions (GP09 and GP16) were significantly higher than those for particulate C and N, and substantially exceeded the corresponding values in EXPORTS, quantitatively confirming strong regional differences in the preferential remineralization of P relative to C and N. A conceptual model of latitudinal differences in vertical particle remineralization was constructed, revealing that the surface nutrient regime profoundly shapes the vertical evolution of particulate C:P ratios by modulating microbial demand for P remineralization in the twilight zone, and highlighting the pivotal role of differential P cycling in linking surface ecological processes to deep carbon export. This study provides crucial observational constraints for improving the parameterization of particle remineralization in ocean biogeochemical models.

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