Trace metals (e.g., Zn, Mn, Ni, Cu, Co, and Cd) are essential micronutrients that influence ocean productivity and biogeochemistry. The metal quotas of phytoplankton provide valuable insights into both the physiological demand for these metals and the environmental conditions under which cells grow. However, most available metal quota data are derived from laboratory culture experiments and are commonly regarded as fixed stoichiometric values, which may not fully represent those in natural populations. In this study, we investigates particulate trace metal-to-phosphorus (M:P) stoichiometries along two transects (155°E and 165°E) spanning 10°N–50°N in the Northwest Pacific Ocean. Suspended particles were collected using large volume in situ pumps aboard R/V Tan Kah Kee during three cruises (KK2003, KK2202, and KK2504). The results reveal distinct latitudinal patterns in phytoplankton-associated metal stoichiometry across the Northwest Pacific. For Cd and Zn, their M:P ratios increased from 0.03 and 0.3 pmol:nmol at ＜25°N to 0.6 and 6.9 pmol:nmol at ＞45°N, respectively, indicating enhanced Cd and Zn requirements under high latitude conditions. In contrast, Co exhibited an opposite pattern, with relatively elevated Co:P ratios at lower latitudes (0.25 pmol:nmol at 12.5°N) but remaining relatively low (0.03–0.15 pmol:nmol) at higher latitude. For Mn, Cu, and Ni, although their particulate concentrations in the upper 100 m increased toward higher latitudes in parallel with increasing particulate phosphorus concentrations, their M:P ratios showed no clear latitudinal trends. This lack of variation may reflect either intrinsically stable metal requirements or stronger contributions from non-biological particulate components that obscure biological signals. These contrasting elemental responses highlight the heterogeneous controls of environmental conditions and phytoplankton community structure on marine metal stoichiometry.

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