Devaleraea ramentacea represents one of the few red macroalgal species endemic to the Arctic. Previous unifactorial experiments revealed a generally high tolerance of D. ramentacea to variation in abiotic conditions. Although in the field the effects of photosynthetically active (PAR) and UV-radiation, temperature and salinity are usually interconnected, studies on interactive effects on its physiology are scarce. Mesocosm-experiments under natural solar radiation as well as laboratory set-ups under defined, artificial radiation conditions were conducted at Spitsbergen in order to reveal physiological responses of D. ramentacea under multiple abiotic stress. The algae were exposed to experimental treatments with/without UV-radiation, at three different water temperatures and at different salinities. In each treatment, photosynthetic performance was monitored by PAM chlorophyll fluorescence measurements and algal fragments were conserved for later biochemical analysis. Photosynthetic measurements confirm the high tolerance of adult sporophytes of D. ramentacea towards single and combined stress factors. Experimentally induced changes in the content of UV-screening mycosporine-like amino acids (MAA) and the enzymatic activity of superoxid-dimutase were studied. A specific characteristic of D. ramentacea under changing abiotic conditions is the greening of the tips. The factors inducing the loss of phycobiliproteins and the changes in physiological performance in the affected thallus fragments are addressed. Results will be discussed in the context of the species distributional patterns.