Nitrogen (N) transformations and fluxes at the sediment‐water interface (SWI) were measured in Missisquoi Bay, Lake Champlain, to clarify the role of N in cyanobacterial blooms in temperate, eutrophic lakes. N sources (e.g., N fixation and tributary inputs), sinks (e.g., denitrification/anammox), and internal “links” (e.g., dissimilatory reduction to ; DNRA) were evaluated at a river discharge (PRM) and in the central basin (M...