The Siberian Arctic ecosystem is experiencing significant changes due to increasing freshwater input, changes in water mass distribution, and varying anthropogenic pressures. This proposal integrates key microscale biogeochemical (MPs, trace metals) and food web (phytoplankton, zooplankton, and the microbial loop) components, to provide an understanding of how these environmental processes interact and impact ecosystem services (e.g. productivity) within the region. The observations will be conducted on the planned for the Nansen and Amundsen Basins Observational System (NABOS) cruise. Key advancements include determining the role of riverine inputs in delivering trace nutrients and MPs to Arctic seas, how sea ice processes dictate the distribution of these elements and compounds, and how these influences control net ecosystem productivity and lower trophic level species composition. This research will provide novel, full water column measurements of trace metals, MPs, and lower trophic level dynamics, including species composition, phytoplankton pigments, total and active cell abundances, net microbial productivity and respiration rates in the East Siberian and Laptev seas. Specifically, we will assess the sources and sinks of trace metals (Fe, Mn, Cu, Ni, Cd, Zn, Pb) and MPs in the coastal Arctic marine ecosystem; describe microbial (bacteria, phytoplankton) species composition and metabolism across varying biogeochemical and salinity regimes; assess phytoplankton taxono