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The distribution of the endemic brown alga Fucus virsoides was assessed along the northern Adriatic coastline. A high-resolution geographic information system database was created using visual census methods to identify the presence and abundance of algae, including the geomorphology of the substrate. Samples of F. virsoides were collected for analysis of the quantitative spatial distribution. The abundance of F. virsoides was related to several environmental variables, including the relative exposure index (REI). The results support the hypothesis that the distribution of F. virsoides in the Gulf of Trieste is influenced mainly by the stability of mediolittoral substrata, wave exposure and the vicinity of freshwater inputs. Populations of this species are widespread in the Gulf of Trieste. Many of them were found growing inside small harbours or along a boatyard, where fluctuations in salinity and nutrient concentrations are frequent. Therefore, we conclude that F. virsoides cannot be considered an ecological indicator for seawater pollution nor for climate change, since it is subjected naturally to high pollution levels and environmental variability.