The Western Antarctic Peninsula (WAP) is a hotspot for changes caused by humans. The total column ozone is not expected to increase in the next several decades leading to an increased UVB radiation at the earth’s surface and, hence, on polar organisms. Global warming is accelerated at the WAP in comparison with the global mean and in some areas water temperatures have risen by 2°C in the last 50 years. Seaweeds are an essential part of the polar coastal ecosystem showing a high level of endemism. Little is known how these communities react on stressors such as UV radiation, light intensity, increasing temperatures and sedimentation and decreased salinity (from the melt water run-off from the glaciers). A variety of field and laboratory experiments on seaweed communities and young developmental stages (spores) were performed over the last ten years in order to tackle this question. A focus was lying on the interactive effects of various variables such as UV and grazing or temperature, sedimentation and grazing and the effect of light and temperature among others. We also performed long term colonization experiments over 4 years to elucidate the general patterns of polar seaweed succession. Interactive effects occurred for example between grazing and UV radiation in field experiments and between temperature and light intensity in laboratory experiments. Other data are currently analyzed. Our results showed that juvenile stages are especially vulnerable to environmental perturbations and that the degree of susceptibility is species-specific. Shift in community structure as a response to environmental change are likely to occur with yet unknown consequences for the associated heterotrophic organisms.