Benthic fluxes are important sources of nutrients and dissolved carbon to the water column. Yet, most approaches for quantifying benthic fluxes are labor intensive and cover relatively small areas of the ocean. Here, we use 224 Ra to quantify ecosystem‐scale vertical mixing across a largely hypoxic deep water column in the Baltic Sea and related benthic Si fluxes. Bottom water profiles from 50 stations along a ~ 5000 km cruise...