Global warming is affecting the Antarctic continent in complex ways. Because Antarctic organisms are specialized to living in the cold, they are vulnerable to increasing temperatures, though quantitative analyses of this issue are currently lacking. Here we compiled a total of 184 estimates of heat tolerance belonging to 39 marine species and quantified how survival is affected concomitantly by the intensity and duration of a thermal stress. Species exhibit thermal limits displaced towards colder temperatures, with contrasting strategies between arthropods and fish that exhibit low tolerance to acute heat challenges, and brachiopods, echinoderms and molluscs that tend to be more sensitive to chronic exposure. These differences might be associated with mobility. A dynamic mortality model suggests that Antarctic organisms already encounter temperatures that might be physiologically stressful and indicate that these ecological communities are indeed vulnerable to ongoing rising temperatures.

We performed an extensive review of the literature and built a database of heat tolerance for marine organisms distributed in the Southern Ocean (i.e., south of 60° S latitude). We started by retrieving information published in previous reviews on the subject, and combined the original sources from these reviews with more recent published references found with a Boolean search in ISI Web of Science with the following keywords: ‘thermal tolerance’ or ‘Antarctic animals’ or ‘CTmax’ or ‘thermal limits’ or ‘heat tolerance’. The search for heat tolerance ended in August 2020. The resulting dataset was combined with high-resolution ambient temperature data records, obtained in intertidal and subtidal Antarctic environments, to estimate thermal mortality in field conditions.

All analyses were performed with open source R (https://cran.r-project.org/)