During a survey in September 2010 in Tjärnö, Sweden, we examined differences in the occurrence of the barnacle Semibalanus balanoides at rocky shores. We sought to proof whether there were differences in the density of S. balanoides in habitats depending either on wave energy or on orientation of the rocks facing north and south respectively. Data analysis showed no differences in occurrence of the barnacles depending on wave energy in the habitat. In contrast there is a significant difference

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... etween examined rock faces with opposite orientation. Habitats with northerly orientation harboured greatly more individuals of S. balanoides than southerly orientated habitats. These results indicate that several factors influence the occurrence of barnacles in habitats connected to orientation. We suggest that there is a correlation between solar exposure, which influences thermal stress and the risk of desiccation and the frequency of occurrence of S. balanoides.