Nutrients play a fundamental role in regulating primary production (PP) and biological carbon pump efficiency in the Arctic Ocean. However, under rapid climate warming, trends in PP and nutrient dynamics in the East Siberian Sea (ESS), a critical shelf region, remain poorly constrained. In this study, we combine hydrochemical data from the first China-Russia joint Arctic expedition (2016) with historical observations (GLODAPv2, 2008) to assess changes in nutrient inventories and their biogeochemical drivers over the span of eight years. Results show that dissolved silicon (DSi), dissolved inorganic phosphate (DIP), and nitrate (NO₃⁻) inventories in the ESS shelf declined significantly by 410.24, 21.95, and 138.03 mmol m⁻², respectively. Analysis using end-member mixing and Monte Carlo simulation revealed no substantial shift in water mass contributions between 2008 and 2016: riverine input (11.65% vs. 15.17%), sea ice meltwater (−0.26% vs. 1.91%), Atlantic Water (19.05% vs. 30.15%), and Pacific Water (66.03% vs. 56.14%). By reconstructing pre-bloom DSi concentrations and estimating net biological utilization, we determined that diatom-driven changes in net primary productivity (∆NPP) led to an increase of 15.49−23.84 Tg C on ESS shelf during 2008−2016. Our findings suggest that the observed decline in DSi inventory reflects enhanced biological uptake, resulting in a significant rise in PP concurrent with sea ice retreat. This implies that Arctic marginal seas may partially offset climate warming through intensified biological carbon sequestration.