C. Gonzalez-Silva R.A. Mancilla L. Salas R.E. Palma J.J. Wynne C.P. McKay R. Vicuna A. Azua-Bustos 2009 Caves offer a stable and protected environment from harsh and changing outside prevailing conditions. Hence, they represent an interesting habitat for studying life in extreme environments. Here, we report the presence of a member of the ancient eukaryote red algae Cyanidium group in a coastal cave of the hyperarid Atacama Desert. This microorganism was found to form a seemingly monospecific biofilm growing under extremely low photon flux levels. Our work suggests that this species, Cyanidium sp. Atacama, is a new member of a recently proposed novel monophyletic lineage of mesophilic "cave" Cyanidium sp., distinct from the remaining three other lineages which are all thermo-acidophilic. The cave described in this work may represent an evolutionary island for life in the midst of the Atacama Desert. ?? Springer Science + Business Media, LLC 2009. application/pdf 10.1007/s00248-009-9500-5 en Ancient photosynthetic eukaryote biofilms in an Atacama Desert coastal cave article