Description: There is a general lack of information on the succession of marine benthic algae in Antarctica. We performed two colonization experiments in the upper subtidal (3 and 5 metres depth) using artificial substrates in Potter Cove (South Shetland Islands): in the outer cove, an area mainly unaffected by sedimentation, and in the inner cove, in close proximity to a retreating glacier, with high sediment inflow particularly during the melting season. Seasonal and interannual changes in total, diatom and macroalgal cover, species composition and ecological indexes were assessed over four years. Tiles were analysed in spring and summer in the laboratory and by year-round photographic monitoring. Irradiance (photosynthetically active radiation and ultraviolet radiation), salinity and temperature were monitored on a monthly basis. Benthic algae dominated the assemblages, with macroalgae reaching ~70% cover after two years. There were site and temporal differences in the contribution of diatom mats (mainly pennate forms) and macroalgal cover. Diatom cover was higher at the glacier-influenced site, particularly at the early stages, and decreased significantly with time. Between years, macroalgal assemblages changed significantly in a site-specific manner. Assemblages mainly comprised annual and pseudoperennial species at both sites, with absence of adult large Desmarestiales. Although a year separated the establishment of the two experiments, there were convergence patterns in the changes of cover over time - that seemed to be controlled by competitive interactions - and in the patterns of species replacement. However, the inner cove site exhibited lower number of macroalgal taxa and a tendency to decreased diversity over time that could be related to higher the level of stress and disturbance caused by glacial influence.