The objective was to investigate functional changes of macrobenthic communities along the salinity gradient in the south-western Baltic Sea. Two different approaches were chosen: (1) the appraisal of functional diversity and composition and (2) mapping species biomass as a basic tool for quantification of single key functions. A distinct shift of the functional composition was detected. In contrast, a potential shift in functional diversity was buffered by the dominance of ubiquitous species. Quantitative distribution maps were drawn for important bivalve species.