The aim of this study is to understand the macroalgal vertical zonation at Potter Cove (Isla 25 de Mayo/ King George Island) in five selected areas with different degree of glacial influence, and thus a different degree of sedimentation, from a physiological point of view. From December 2009 to March 2010, five macroalgal species (Desmarestia anceps, Himantothallus grandifolius, Ascoseira mirabilis, Iridaea cordata and Palmaria decipiens) were sampled at 5, 10, 20 and 30 m depth. After collection, photosynthetic parameters and chlorophyll a content were determined. In areas with high glacial influence the maximal vertical distribution limit of all species was 10 m depth, while in areas with intermediate and low/none glacial impact, it was 20 and 30 m depth, respectively. Areas with high glacial influence presented limiting light conditions below 20 m depth coinciding with the absence of macroalgae. In intermediate and low disturbed areas, light intensities were not limiting. Palmaria decipiens was the only studied species showing lower light saturation points at deeper depths. Chl a content did not show significant differences with increasing depth. Our first results show that the vertical zonation of the studied species is positively correlated to the light penetration which decreases as the glacial influence (as production of sediment input) increases. A further increase of sedimentation due to global warming will undoubtedly lead to an elevation of the lower distribution limit of the studied species and will probably have a great effect on macroalgal primary productivity in Potter Cove.