Particulate phosphorus (P) cycling is closely linked to organic carbon export and carbon sequestration in the ocean. Previous studies have suggested that atmospheric deposition may enhance the biological pump in the Kuroshio Extension region of the Northwestern Pacific. Although dust is recognized as an important nutrient source in the open ocean, its influence on particulate phosphorus in sinking particles remains poorly constrained. We analyzed 21 sinking particle samples collected at 10- or 30-day intervals from August 2018 to August 2019. The samples were obtained from sediment traps deployed at 900 m and 4100 m at station KE08 in the Northwestern Pacific (33°41.8'N, 156°39.7'E; water depth: 5,330 m). Phosphorus was separated into five operationally defined fractions: total P, organic P, inorganic P, HCl-extractable P, and NaOH-extractable P. The contents of CaCO₃, lithogenic material, and opal were estimated from inorganic carbon, Al, and Si contents, respectively. Satellite-derived net primary production and MERRA-2 atmospheric deposition data were also considered. At 900 m, Ti/Al ratios of sinking particles were comparable to those reported for continental dust source materials, and dust flux was positively correlated with lithogenic flux. Lithogenic flux at 900 m showed positive correlations with POC flux and the fluxes of individual P fractions. However, higher lithogenic flux did not correspond to a clear shift in P composition. Temporal variations in the C:OP ratio were similar to those in POC flux and showed a negative correlation with opal content. On average, the proportions of organic P and inorganic P relative to total P were similar between 900 m and 4100 m, whereas proportion of HCl-extractable P relative to total P increased and that of NaOH-extractable P decreased at 4100 m relative to 900 m.
 

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