Bangia atropurpurea (Mertens ex Roth) C. Agardh is a freshwater red alga species that is distributed worldwide. B. atropurpurea is highly adaptable due to its stress-tolerance, which ensures survival under desiccation periods and under radiation extremes typical of the supra- and upper eulittoral zones. Whereas a number of previous investigations addressed some of the physiological and biochemical traits involved in stress-tolerance, we studied the spatial arrangement of the mature (multiseriate) and immature (uniseriate) filaments and of selected bioorganic compounds along a gradient defined by distance from the waterline. Substantial physiological and biochemical differences were previously observed among phenological stages in the marine environment. In this study, we showed a nonrandom spatial structure of both phenological stages and photosynthetic pigments and photoprotective compounds, R-phycocyanin and R-phycoerythrin along the supralittoral-eulittoral gradient. This observed pattern strongly suggests a complex interplay between physio-morphological regulation and spatial arrangement of mature and immature filaments in conferring the typical stress tolerance of B. atropurpurea.