Abstract
Intertidal algae have to cope with diurnally and seasonally fluctuating environmental factors such as salinity, temperature, dehydration, and light. In New Zealand, solar radiation, including the ultraviolet wavelengths, is also an important stress factor for such algae. Therefore, two native ( Bostrychia arbuscula W.H.Harvey [Ceramiales], Champia novae-zelandiae (J.D.Hooker & Harvey) Harvey [Rhodymeniales]) and one introduced red algal taxon ( Schizymenia spp. J. Agardh [Nemastomatales]) were investigated over 12 months in terms of stress metabolites which contribute to ultraviolet radiation (UVR) and salinity tolerance. Mycosporine-like amino acids (MAAs), which act as sunscreens, and organic osmolytes were qualitatively and quantitatively analyzed. Porphyra-334, shinorine, and palythine were the most dominant MAAs yet distributed differently among the species. B. arbuscula showed a correlation between photosynthetically active radiation (PAR)/UVR and slightly higher MAA concentrations in summer. In contrast, C. novae-zelandiae displayed the lowest level of MAAs in summer, and no correlation was found between MAA values and solar radiation. In Schizymenia spp., the highest MAA amounts were found in summer, and for most months, a correlation with PAR/UV radiation was visible. While digeneaside and sorbitol were the dominant organic osmolytes in B. arbuscula , floridoside occurred in C. novae-zelandiae and Schizymenia spp. Only B. arbuscula exhibited higher organic osmolyte concentrations in summer. In contrast, floridoside contents in C. novae-zelandiae and Schizymenia spp. were low and highly variable over the course of the seasons. Our data indicate that both native red algal species are well acclimated to the intertidal zone. For the introduced Schizymenia spp., a more narrow salinity tolerance can be assumed, while the high MAA values may explain its establishment in New Zealand.