Stress Tolerance of the Endemic Antarctic Brown Alga Desmarestia anceps to UV Radiation and Temperature is Mediated by High Concentrations of Phlorotannins

The endemic Antarctic brown macroalga Desmarestia anceps is strongly shade adapted, but shows also a high capacity to cope with different environmental stressors, e.g. UV radiation and temperature. Therefore this species colonizes wide depth gradients, which are characterized by changing environmental conditions. In the present study, we examine whether the different physiological abilities allowing D. anceps to grow across a wide depth range is determined by high levels of phlorotannins. Photosynthesis, measured by PAM-fluorometry, the contents of soluble phlorotannins, antioxidant capacities of field-grown were analysed in response to different conditions of radiation (PAR and PAR+UV) and temperature (2, 7 and 12°C). The results show that maximal quantum of fluorescence (Fv/Fm) decreased with increasing doses of UV radiation but remained unaffected by temperature. High levels of soluble phlorotannins were detected and confirmed by microscopic observation revealing the abundance of large physodes. Exposure to UV radiation and elevated temperature showed that phlorotannins were not inducible by UV but increased at 12°C. ROS scavenging capacity was positively correlated with the contents of phlorotannins. In general, highest contents of phlorotannins were correlated with the lowest inhibition of Fv/Fm in all experimental treatments, highlighting the UV-protective role of these compounds in D. anceps. This article is protected by copyright. All rights reserved.