© 2015 British Phycological Society. Many species of macroalgae along the western Antarctic Peninsula have a high coverage of filamentous algal endophytes. A previous field study showed that endophyte presence negatively impacts growth and survival in some Antarctic algae, but can have no impact on others. We examined nine species of common macroalgal hosts from the area surrounding Palmer Station, Antarctica, to examine fine-scale impacts of endophyte presence on host physiology. Physiological parameters were selected based on their potential to influence fitness of host algae. These included photosynthetic parameters, thallus toughness and susceptibility to grazers in those species previously known to be chemically defended. We found that few macroalgal hosts are impacted by the presence of endophytes and that these impacts are not consistent across all physiological parameters. Iridaea cordata and Pachymenia sp. were the only species among the nine examined that demonstrated physiological stress in the presence of endophytes. Out of four species in a previous study, I. cordata was also the most heavily impacted by endophyte presence.